diff --git a/CREDITS b/CREDITS
index 6c59f6dc..e946331d 100644
--- a/CREDITS
+++ b/CREDITS
@@ -233,3 +233,8 @@ N: Waterfox
 W: https://github.com/WaterfoxCo/Waterfox
 C: Copyright (c) 2012 Waterfox Limited
 L: MPL 2.0
+
+N: WaveFox
+W: https://github.com/QNetITQ/WaveFox
+C: Copyright (c) 2021 QNetITQ
+L: MIT
diff --git a/css/leptonChrome.css b/css/leptonChrome.css
index ddc454b0..10b24658 100644
--- a/css/leptonChrome.css
+++ b/css/leptonChrome.css
@@ -137,9 +137,9 @@
 
   /* Navbar Border */
   #navigator-toolbox:-moz-lwtheme {
-    --tabs-border-color: rgba(0, 0, 0, 0.3);
-    /* Legacy: v96 */
-    --lwt-tabs-border-color: rgba(0, 0, 0, 0.3);
+    --tabs-border-color: rgba(0, 0, 0, 0.4);
+    /* Legacy: v96, (0, 0, 0, 0.3) -> (0, 0, 0, 0.4)  */
+    --lwt-tabs-border-color: rgba(0, 0, 0, 0.4);
   }
 
   /*= Findbar Border Color =====================================================*/
@@ -6391,24 +6391,35 @@
 }
 /*= Multi Selected Color - More Contrast =====================================*/
 @supports -moz-bool-pref("userChrome.tab.multi_selected") {
+  #TabsToolbar {
+    --uc-multiselected-tab-bgcolor: color-mix(in srgb, currentColor 28%, var(--toolbar-bgcolor, transparent));
+  }
+  #TabsToolbar[brighttext] {
+    --uc-multiselected-tab-bgcolor: color-mix(in srgb, currentColor 16%, var(--toolbar-bgcolor, transparent));
+  }
+
   #tabbrowser-tabs:not([movingtab])
     > #tabbrowser-arrowscrollbox
     > .tabbrowser-tab
     > .tab-stack
-    > .tab-background[multiselected]:not([selected]):-moz-lwtheme {
-    background-image: linear-gradient(var(--toolbar-bgcolor, transparent), var(--toolbar-bgcolor, transparent)),
-      linear-gradient(var(--toolbar-bgcolor), var(--toolbar-bgcolor)), var(--lwt-header-image, none) !important;
-  }
-
-  .tab-background[multiselected="true"]:not([selected="true"]) > .tab-loading-burst:not([bursting]) {
-    background: color-mix(in srgb, currentColor 65%, transparent);
-    opacity: 0.3;
-  }
-
-  #TabsToolbar[brighttext]
-    .tab-background[multiselected="true"]:not([selected="true"])
-    > .tab-loading-burst:not([bursting]) {
-    opacity: 0.15;
+    > .tab-background[multiselected]:not([selected]) {
+    /* Original:
+    background-attachment: scroll, scroll, fixed;
+    background-color: transparent;
+    background-image: linear-gradient(var(--lwt-selected-tab-background-color, transparent), var(--lwt-selected-tab-background-color, transparent)),
+                      linear-gradient(var(--toolbar-bgcolor), var(--toolbar-bgcolor)),
+                      var(--lwt-header-image, none);
+    background-position: 0 0, 0 0, right top;
+    background-repeat: repeat-x, repeat-x, no-repeat;
+    background-size: auto 100%, auto 100%, auto auto;
+    */
+    background-attachment: scroll, fixed !important;
+    background-color: transparent !important;
+    background-image: linear-gradient(var(--uc-multiselected-tab-bgcolor), var(--uc-multiselected-tab-bgcolor)),
+      var(--lwt-header-image, none) !important;
+    background-position: 0 0, right top !important;
+    background-repeat: repeat-x, no-repeat !important;
+    background-size: auto 100%, auto auto !important;
   }
 
   @supports -moz-bool-pref("userChrome.tab.connect_to_window") {
@@ -6431,40 +6442,70 @@
 }
 /*= Selected Tab - Box Shadow ================================================*/
 @supports -moz-bool-pref("userChrome.tab.box_shadow") {
-  #TabsToolbar[brighttext]
+  #TabsToolbar {
+    --uc-tab-background-shadow-soft: 0 0 1px;
+    --uc-tab-background-shadow-hard: 0 0 0 1px;
+    --uc-tab-shadow-color: var(
+      --tab-line-color,
+      var(--lwt-tab-line-color, var(--tabs-border-color, rgba(128, 128, 142, 0.9)))
+    );
+    --uc-tab-shadow-color-bundle: var(--tab-line-color, var(--lwt-tab-line-color, rgba(128, 128, 142, 0.9)));
+    --uc-tab-basic-shadow: 0 0 4px rgba(0, 0, 0, 0.4);
+    --uc-tab-additional-shadow: 0 0 4px rgba(128, 128, 142, 0.5);
+  }
+  @supports -moz-bool-pref("userChrome.tab.bottom_rounded_corner") {
+    @supports -moz-bool-pref("userChrome.tab.bottom_rounded_corner.wave") or -moz-bool-pref(
+        "userChrome.tab.bottom_rounded_corner.australis"
+      ) or -moz-bool-pref("userChrome.tab.bottom_rounded_corner.chrome_legacy") or -moz-bool-pref(
+        "userChrome.tab.bottom_rounded_corner.chrome"
+      ) or -moz-bool-pref("userChrome.tab.bottom_rounded_corner.edge") {
+      #TabsToolbar {
+        --uc-tab-background-shadow-hard: 0 -1px 0;
+        --uc-tab-basic-shadow: 0 -1px 0px rgba(0, 0, 0, 0.4);
+        --uc-tab-additional-shadow: 0 0 0 transparent;
+      }
+    }
+  }
+
+  #tabbrowser-tabs:not([noshadowfortests]) .tab-background:is([selected], [multiselected]) {
+    box-shadow: var(--uc-tab-basic-shadow) !important;
+  }
+
+  :root:is([lwtheme-mozlightdark], [style*="--lwt-accent-color: rgb(28, 27, 34); --lwt-text-color: rgba(251, 251, 254);"])
+    #TabsToolbar[brighttext]
     #tabbrowser-tabs:not([noshadowfortests])
-    .tabbrowser-tab[visuallyselected="true"]:not(:focus)
-    > .tab-stack
-    > .tab-background:-moz-lwtheme {
+    .tabbrowser-tab {
     /* Original: 0 0 1px var(--tab-line-color, rgba(128,128,142,0.9))
          Bright: 0 0 1px var(--tab-line-color, rgba(128,128,142,0.9)), 0 0 4px rgba(128,128,142,0.5) */
-    box-shadow: 0 0 1px var(--toolbar-color) !important;
+    /* Consider 0 0 4px rgba(128,128,142,0.9) -> 0 0 4px rgba(0,0,0,.4) new default */
   }
-
-  #TabsToolbar[brighttext]
+  :root:is([lwtheme-mozlightdark], [style*="--lwt-accent-color: rgb(28, 27, 34); --lwt-text-color: rgba(251, 251, 254);"])
+    #TabsToolbar[brighttext]
     #tabbrowser-tabs:not([noshadowfortests])
-    .tabbrowser-tab[multiselected]:not([visuallyselected])
+    .tabbrowser-tab:is([selected], [multiselected])
     > .tab-stack
     > .tab-background:-moz-lwtheme {
-    box-shadow: 0 0 1px color-mix(in srgb, var(--toolbar-color) 80%, transparent) !important;
+    box-shadow: var(--uc-tab-background-shadow-soft) var(--uc-tab-shadow-color) !important;
   }
-
-  /* Consider 0 0 4px rgba(128,128,142,0.9) -> 0 0 4px rgba(0,0,0,.4) new default */
-  #TabsToolbar:not([brighttext])
+  :root:is([lwtheme-mozlightdark], [style*="--lwt-accent-color: rgb(28, 27, 34); --lwt-text-color: rgba(251, 251, 254);"])
+    #TabsToolbar[brighttext]
     #tabbrowser-tabs:not([noshadowfortests])
-    .tabbrowser-tab:is([visuallyselected="true"], [multiselected])
-    > .tab-stack
-    > .tab-background {
-    box-shadow: 0 0 1px var(--tab-line-color, var(--lwt-tab-line-color, rgba(128, 128, 142, 0.9))),
-      0 0 4px rgba(128, 128, 142, 0.5) !important;
+    .tabbrowser-tab[visuallyselected="true"]:not(:focus),
+  :root:is([lwtheme-mozlightdark], [style*="--lwt-accent-color: rgb(28, 27, 34); --lwt-text-color: rgba(251, 251, 254);"])
+    #TabsToolbar[brighttext]
+    #tabbrowser-tabs:not([noshadowfortests])
+    .tabbrowser-tab[multiselected]:not([visuallyselected]) {
+    --uc-tab-shadow-color: var(--toolbar-color);
   }
 
-  #TabsToolbar[brighttext]
+  :root:is([lwtheme-mozlightdark], [style*="--lwt-accent-color: rgb(240, 240, 244); --lwt-text-color: rgba(21, 20, 26);"])
+    #TabsToolbar:not([brighttext])
     #tabbrowser-tabs:not([noshadowfortests])
-    .tabbrowser-tab:is([visuallyselected="true"], [multiselected])
+    .tabbrowser-tab:is([visuallyselected], [multiselected])
     > .tab-stack
-    > .tab-background:-moz-lwtheme {
-    box-shadow: 0 0 1px var(--tab-line-color, var(--lwt-tab-line-color, rgba(128, 128, 142, 0.9))) !important;
+    > .tab-background {
+    --uc-tab-shadow-color: var(--uc-tab-shadow-color-bundle);
+    box-shadow: var(--uc-tab-background-shadow-soft) var(--uc-tab-shadow-color), var(--uc-tab-additional-shadow) !important;
   }
 
   /* For themes outside of Light and Dark (which are curated by Mozilla), show a thicker border
@@ -6475,9 +6516,7 @@
     .tabbrowser-tab:is([visuallyselected="true"], [multiselected])
     > .tab-stack
     > .tab-background:-moz-lwtheme {
-    box-shadow: 0 0 0 1px
-        var(--tab-line-color, var(--lwt-tab-line-color, var(--tabs-border-color, rgba(128, 128, 142, 0.9)))),
-      0 0 4px rgba(128, 128, 142, 0.5) !important;
+    box-shadow: var(--uc-tab-background-shadow-hard) var(--uc-tab-shadow-color), var(--uc-tab-additional-shadow) !important;
   }
 
   :root:not([lwtheme-mozlightdark], [style*="--lwt-accent-color: rgb(28, 27, 34); --lwt-text-color: rgba(251, 251, 254);"])
@@ -6486,135 +6525,380 @@
     .tabbrowser-tab:is([visuallyselected="true"], [multiselected])
     > .tab-stack
     > .tab-background:-moz-lwtheme {
-    box-shadow: 0 0 0 1px
-      var(--tab-line-color, var(--lwt-tab-line-color, var(--tabs-border-color, rgba(128, 128, 142, 0.9)))) !important;
+    box-shadow: var(--uc-tab-background-shadow-hard) var(--uc-tab-shadow-color) !important;
   }
 }
 /*= Selected Tab - Bottom Rounded Corner =====================================*/
 @supports -moz-bool-pref("userChrome.tab.bottom_rounded_corner") {
-  #tabbrowser-tabs {
-    --tab-corner-rounding: 3px;
-    /* 10px looks about like chromium - 17px looks close to Australis tabs */
-    --tab-corner-padding: 0px;
-    --tab-corner-position: calc(var(--tab-corner-padding) - var(--tab-corner-rounding));
-  }
+  @supports not -moz-bool-pref("userChrome.tab.bottom_rounded_corner.wave") {
+    @supports not -moz-bool-pref("userChrome.tab.bottom_rounded_corner.australis") {
+      @supports not -moz-bool-pref("userChrome.tab.bottom_rounded_corner.chrome") {
+        @supports not -moz-bool-pref("userChrome.tab.bottom_rounded_corner.chrome_legacy") {
+          @supports not -moz-bool-pref("userChrome.tab.bottom_rounded_corner.edge") {
+            #TabsToolbar {
+              --uc-tab-corner-rounding: 3px;
+              /* 10px looks about like chromium - 17px looks close to Australis tabs */
+              --uc-tab-corner-padding: 0px;
+              --uc-tab-corner-position: calc(var(--uc-tab-corner-padding) - var(--uc-tab-corner-rounding));
+              --uc-tab-corner-left-side-svg: url("../icons/tab-bottom-corner-left.svg");
+              --uc-tab-corner-right-side-svg: url("../icons/tab-bottom-corner-right.svg");
+            }
 
-  :root:not([customizing="true"]) .tabbrowser-tab .tab-background::before,
-  :root:not([customizing="true"]) .tabbrowser-tab .tab-background::after {
-    /* Box */
-    display: block;
-    position: absolute;
-    z-index: 1;
-    bottom: 0;
-    /* Shape */
-    width: var(--tab-corner-rounding);
-    height: 100%;
-    /* Color */
-    fill: transparent;
-    stroke: transparent;
-    -moz-context-properties: fill, stroke;
-    /* Image */
-    background-size: var(--tab-corner-rounding);
-    background-repeat: no-repeat;
-    background-position-y: bottom;
-  }
-  @supports -moz-bool-pref("userChrome.tab.bottom_rounded_corner.all") {
-    :root:not([customizing="true"]) .tabbrowser-tab .tab-background::before,
-    :root:not([customizing="true"]) .tabbrowser-tab .tab-background::after {
-      content: "";
+            :root:not([customizing="true"]) .tabbrowser-tab .tab-background::before,
+            :root:not([customizing="true"]) .tabbrowser-tab .tab-background::after {
+              /* Box */
+              display: block;
+              position: absolute;
+              z-index: 1;
+              bottom: 0;
+              /* Shape */
+              width: var(--uc-tab-corner-rounding);
+              height: 100%;
+              /* Color */
+              fill: transparent;
+              stroke: transparent;
+              -moz-context-properties: fill, stroke;
+              /* Image */
+              background-size: var(--uc-tab-corner-rounding);
+              background-repeat: no-repeat;
+              background-position-y: bottom;
+            }
+            @supports -moz-bool-pref("userChrome.tab.bottom_rounded_corner.all") {
+              :root:not([customizing="true"]) .tabbrowser-tab .tab-background::before,
+              :root:not([customizing="true"]) .tabbrowser-tab .tab-background::after {
+                content: "";
+              }
+            }
+            @supports not -moz-bool-pref("userChrome.tab.color_like_toolbar") {
+              :root:not([customizing="true"]) .tabbrowser-tab .tab-background::before,
+              :root:not([customizing="true"]) .tabbrowser-tab .tab-background::after {
+                /* Based on tab background
+                   background-image: linear-gradient(var(--lwt-selected-tab-background-color, transparent), var(--lwt-selected-tab-background-color, transparent)), linear-gradient(var(--toolbar-bgcolor), var(--toolbar-bgcolor)), var(--lwt-header-image, none);
+
+                   defaults
+                   background-color: var(--tab-selected-bgcolor, var(--toolbar-bgcolor));
+                   background-image: var(--tab-selected-bgimage, var(--toolbar-bgimage));
+                */
+                fill: var(
+                  --lwt-selected-tab-background-color,
+                  var(--tab-selected-bgcolor, var(--toolbar-bgcolor))
+                ) !important;
+              }
+            }
+            :root:not([customizing="true"]) .tabbrowser-tab .tab-background::before {
+              left: var(--uc-tab-corner-position);
+              background-image: var(--uc-tab-corner-left-side-svg);
+            }
+            :root:not([customizing="true"]) .tabbrowser-tab .tab-background::after {
+              right: var(--uc-tab-corner-position);
+              background-image: var(--uc-tab-corner-right-side-svg);
+            }
+            :root:not([customizing="true"]) .tabbrowser-tab[visuallyselected] .tab-background::before,
+            :root:not([customizing="true"]) .tabbrowser-tab[visuallyselected] .tab-background::after {
+              fill: var(--tab-selected-bgcolor, var(--toolbar-bgcolor));
+              stroke: var(--tab-line-color, var(--tabs-border-color, rgba(128, 128, 142, 0.9)));
+            }
+            @supports not -moz-bool-pref("userChrome.tab.bottom_rounded_corner.all") {
+              :root:not([customizing="true"]) .tabbrowser-tab[visuallyselected] .tab-background::before,
+              :root:not([customizing="true"]) .tabbrowser-tab[visuallyselected] .tab-background::after {
+                content: "";
+              }
+            }
+            :root:not([customizing="true"]) .tabbrowser-tab[multiselected] .tab-background::before,
+            :root:not([customizing="true"]) .tabbrowser-tab[multiselected] .tab-background::after {
+              fill: var(--tab-selected-bgcolor, var(--toolbar-bgcolor));
+            }
+            :root:not([customizing="true"])
+              .tabbrowser-tab:hover:not([visuallyselected], [multiselected])
+              .tab-background::before,
+            :root:not([customizing="true"])
+              .tabbrowser-tab:hover:not([visuallyselected], [multiselected])
+              .tab-background::after {
+              fill: color-mix(in srgb, currentColor 11%, transparent);
+            }
+            @supports -moz-bool-pref("userChrome.tab.multi_selected") {
+              :root:not([customizing="true"])
+                .tabbrowser-tab[multiselected]:not([visuallyselected])
+                .tab-background::before,
+              :root:not([customizing="true"])
+                .tabbrowser-tab[multiselected]:not([visuallyselected])
+                .tab-background::after {
+                fill: color-mix(in srgb, currentColor 65%, transparent);
+                opacity: 0.3;
+              }
+            }
+            :root:not([customizing="true"])::is([lwtheme-mozlightdark], [style*="--lwt-accent-color: rgb(28, 27, 34); --lwt-text-color: rgba(251, 251, 254);"])
+              #TabsToolbar[brighttext]
+              #tabbrowser-tabs:not([noshadowfortests])
+              .tabbrowser-tab[visuallyselected]
+              .tab-background:-moz-lwtheme::before,
+            :root:not([customizing="true"])::is([lwtheme-mozlightdark], [style*="--lwt-accent-color: rgb(28, 27, 34); --lwt-text-color: rgba(251, 251, 254);"])
+              #TabsToolbar[brighttext]
+              #tabbrowser-tabs:not([noshadowfortests])
+              .tabbrowser-tab[visuallyselected]
+              .tab-background:-moz-lwtheme::after {
+              /* As Selected Tab - Box Shadow */
+              stroke: var(--toolbar-color);
+            }
+            @media (-moz-gtk-csd-available) {
+              :root:not([customizing="true"]) {
+                /* Fill color for GTK */
+              }
+              :root:not([customizing="true"]):not([lwtheme="true"])
+                .tabbrowser-tab:is([visuallyselected], [multiselected])
+                .tab-background::before,
+              :root:not([customizing="true"]):not([lwtheme="true"])
+                .tabbrowser-tab:is([visuallyselected], [multiselected])
+                .tab-background::after {
+                /* As GTK Toolbar's background-color + background-image
+                 * --toolbar-non-lwt-bgcolor: -moz-dialog;
+                 * --toolbar-non-lwt-bgimage: linear-gradient(rgba(255,255,255,.15), rgba(255,255,255,.15));
+                 */
+                fill: color-mix(in srgb, white 15%, -moz-dialog);
+                stroke: transparent;
+                opacity: 1;
+              }
+              :root:not([customizing="true"]):not([lwtheme="true"])
+                #TabsToolbar[brighttext]
+                .tabbrowser-tab[visuallyselected]
+                .tab-background::before,
+              :root:not([customizing="true"]):not([lwtheme="true"])
+                #TabsToolbar[brighttext]
+                .tabbrowser-tab[visuallyselected]
+                .tab-background::after {
+                stroke: transparent;
+              }
+            }
+          }
+        }
+      }
     }
   }
-  @supports not -moz-bool-pref("userChrome.tab.color_like_toolbar") {
-    :root:not([customizing="true"]) .tabbrowser-tab .tab-background::before,
-    :root:not([customizing="true"]) .tabbrowser-tab .tab-background::after {
-      /* Based on tab background
-         background-image: linear-gradient(var(--lwt-selected-tab-background-color, transparent), var(--lwt-selected-tab-background-color, transparent)), linear-gradient(var(--toolbar-bgcolor), var(--toolbar-bgcolor)), var(--lwt-header-image, none);
-
-         defaults
-         background-color: var(--tab-selected-bgcolor, var(--toolbar-bgcolor));
-         background-image: var(--tab-selected-bgimage, var(--toolbar-bgimage));
-      */
-      fill: var(--lwt-selected-tab-background-color, var(--tab-selected-bgcolor, var(--toolbar-bgcolor))) !important;
+  @supports -moz-bool-pref("userChrome.tab.bottom_rounded_corner.wave") or -moz-bool-pref(
+      "userChrome.tab.bottom_rounded_corner.australis"
+    ) or -moz-bool-pref("userChrome.tab.bottom_rounded_corner.chrome_legacy") or -moz-bool-pref(
+      "userChrome.tab.bottom_rounded_corner.chrome"
+    ) or -moz-bool-pref("userChrome.tab.bottom_rounded_corner.edge") {
+    #TabsToolbar {
+      --uc-tab-corner-height: calc(var(--tab-min-height) + 1px);
+      --uc-tab-corner-size: var(--uc-tab-corner-height);
+      --uc-tab-corner-half-size: calc(var(--uc-tab-corner-size) / 2);
+      --uc-tab-corner-half-size-reverse: calc(var(--uc-tab-corner-half-size) * -1);
+      --uc-tab-corner-bgimage: none;
     }
-  }
-  :root:not([customizing="true"]) .tabbrowser-tab .tab-background::before {
-    left: var(--tab-corner-position);
-    background-image: url("../icons/tab-bottom-corner-left.svg");
-  }
-  :root:not([customizing="true"]) .tabbrowser-tab .tab-background::after {
-    right: var(--tab-corner-position);
-    background-image: url("../icons/tab-bottom-corner-right.svg");
-  }
-  :root:not([customizing="true"]) .tabbrowser-tab[visuallyselected] .tab-background::before,
-  :root:not([customizing="true"]) .tabbrowser-tab[visuallyselected] .tab-background::after {
-    fill: var(--tab-selected-bgcolor, var(--toolbar-bgcolor));
-    stroke: var(--tab-line-color, var(--tabs-border-color, rgba(128, 128, 142, 0.9)));
-  }
-  @supports not -moz-bool-pref("userChrome.tab.bottom_rounded_corner.all") {
-    :root:not([customizing="true"]) .tabbrowser-tab[visuallyselected] .tab-background::before,
-    :root:not([customizing="true"]) .tabbrowser-tab[visuallyselected] .tab-background::after {
-      content: "";
+    @supports -moz-bool-pref("userChrome.tab.bottom_rounded_corner.wave") {
+      #TabsToolbar {
+        --uc-tab-corner-left-side-svg: url("../icons/tab-bottom-corner-left-wave.svg");
+        --uc-tab-corner-left-side-clipPath: url("../icons/tab-bottom-corner-left-wave.svg#svgClipPath");
+        --uc-tab-corner-right-side-svg: url("../icons/tab-bottom-corner-right-wave.svg");
+        --uc-tab-corner-right-side-clipPath: url("../icons/tab-bottom-corner-right-wave.svg#svgClipPath");
+        --uc-tab-corner-left-side-svg-clipped: url("../icons/tab-bottom-corner-left-wave-clipped.svg");
+        --uc-tab-corner-right-side-svg-clipped: url("../icons/tab-bottom-corner-right-wave-clipped.svg");
+      }
     }
-  }
-  :root:not([customizing="true"]) .tabbrowser-tab[multiselected] .tab-background::before,
-  :root:not([customizing="true"]) .tabbrowser-tab[multiselected] .tab-background::after {
-    fill: var(--tab-selected-bgcolor, var(--toolbar-bgcolor));
-  }
-  :root:not([customizing="true"])
-    .tabbrowser-tab:hover:not([visuallyselected], [multiselected])
-    .tab-background::before,
-  :root:not([customizing="true"])
-    .tabbrowser-tab:hover:not([visuallyselected], [multiselected])
-    .tab-background::after {
-    fill: color-mix(in srgb, currentColor 11%, transparent);
-  }
-  @supports -moz-bool-pref("userChrome.tab.multi_selected") {
-    :root:not([customizing="true"]) .tabbrowser-tab[multiselected]:not([visuallyselected]) .tab-background::before,
-    :root:not([customizing="true"]) .tabbrowser-tab[multiselected]:not([visuallyselected]) .tab-background::after {
-      fill: color-mix(in srgb, currentColor 65%, transparent);
-      opacity: 0.3;
+    @supports -moz-bool-pref("userChrome.tab.bottom_rounded_corner.australis") {
+      #TabsToolbar {
+        --uc-tab-corner-left-side-svg: url("../icons/tab-bottom-corner-left-australis.svg");
+        --uc-tab-corner-left-side-clipPath: url("../icons/tab-bottom-corner-left-australis.svg#svgClipPath");
+        --uc-tab-corner-right-side-svg: url("../icons/tab-bottom-corner-right-australis.svg");
+        --uc-tab-corner-right-side-clipPath: url("../icons/tab-bottom-corner-right-australis.svg#svgClipPath");
+        --uc-tab-corner-left-side-svg-clipped: url("../icons/tab-bottom-corner-left-australis-clipped.svg");
+        --uc-tab-corner-right-side-svg-clipped: url("../icons/tab-bottom-corner-right-australis-cilpped.svg");
+      }
     }
-  }
-  :root:not([customizing="true"])::is([lwtheme-mozlightdark], [style*="--lwt-accent-color: rgb(28, 27, 34); --lwt-text-color: rgba(251, 251, 254);"])
-    #TabsToolbar[brighttext]
-    #tabbrowser-tabs:not([noshadowfortests])
-    .tabbrowser-tab[visuallyselected]
-    .tab-background:-moz-lwtheme::before,
-  :root:not([customizing="true"])::is([lwtheme-mozlightdark], [style*="--lwt-accent-color: rgb(28, 27, 34); --lwt-text-color: rgba(251, 251, 254);"])
-    #TabsToolbar[brighttext]
-    #tabbrowser-tabs:not([noshadowfortests])
-    .tabbrowser-tab[visuallyselected]
-    .tab-background:-moz-lwtheme::after {
-    /* As Selected Tab - Box Shadow */
-    stroke: var(--toolbar-color);
-  }
-  @media (-moz-gtk-csd-available) {
-    :root:not([customizing="true"]) {
-      /* Fill color for GTK */
-    }
-    :root:not([customizing="true"]):not([lwtheme="true"])
-      .tabbrowser-tab:is([visuallyselected], [multiselected])
-      .tab-background::before,
-    :root:not([customizing="true"]):not([lwtheme="true"])
-      .tabbrowser-tab:is([visuallyselected], [multiselected])
-      .tab-background::after {
-      /* As GTK Toolbar's background-color + background-image
-       * --toolbar-non-lwt-bgcolor: -moz-dialog;
-       * --toolbar-non-lwt-bgimage: linear-gradient(rgba(255,255,255,.15), rgba(255,255,255,.15));
-       */
-      fill: color-mix(in srgb, white 15%, -moz-dialog);
-      stroke: transparent;
-      opacity: 1;
+    @supports -moz-bool-pref("userChrome.tab.bottom_rounded_corner.chrome") {
+      #TabsToolbar {
+        --uc-tab-corner-left-side-svg: url("../icons/tab-bottom-corner-left-chrome.svg");
+        --uc-tab-corner-left-side-clipPath: url("../icons/tab-bottom-corner-left-chrome.svg#svgClipPath");
+        --uc-tab-corner-right-side-svg: url("../icons/tab-bottom-corner-right-chrome.svg");
+        --uc-tab-corner-right-side-clipPath: url("../icons/tab-bottom-corner-right-chrome.svg#svgClipPath");
+        --uc-tab-corner-left-side-svg-clipped: url("../icons/tab-bottom-corner-left-chrome-clipped.svg");
+        --uc-tab-corner-right-side-svg-clipped: url("../icons/tab-bottom-corner-right-chrome-clipped.svg");
+        --uc-tab-corner-size: 16px;
+      }
+    }
+    @supports -moz-bool-pref("userChrome.tab.bottom_rounded_corner.chrome_legacy") {
+      #TabsToolbar {
+        --uc-tab-corner-left-side-svg: url("../icons/tab-bottom-corner-left-chromeLegacy.svg");
+        --uc-tab-corner-left-side-clipPath: url("../icons/tab-bottom-corner-left-chromeLegacy.svg#svgClipPath");
+        --uc-tab-corner-right-side-svg: url("../icons/tab-bottom-corner-right-chromeLegacy.svg");
+        --uc-tab-corner-right-side-clipPath: url("../icons/tab-bottom-corner-right-chromeLegacy.svg#svgClipPath");
+        --uc-tab-corner-left-side-svg-clipped: url("../icons/tab-bottom-corner-left-chromeLegacy-clipped.svg");
+        --uc-tab-corner-right-side-svg-clipped: url("../icons/tab-bottom-corner-right-chromeLegacy-clipped.svg");
+      }
     }
-    :root:not([customizing="true"]):not([lwtheme="true"])
-      #TabsToolbar[brighttext]
-      .tabbrowser-tab[visuallyselected]
-      .tab-background::before,
-    :root:not([customizing="true"]):not([lwtheme="true"])
-      #TabsToolbar[brighttext]
-      .tabbrowser-tab[visuallyselected]
-      .tab-background::after {
+    @supports -moz-bool-pref("userChrome.tab.bottom_rounded_corner.edge") {
+      #TabsToolbar {
+        --uc-tab-corner-left-side-svg: url("../icons/tab-bottom-corner-left-edge.svg");
+        --uc-tab-corner-left-side-clipPath: url("../icons/tab-bottom-corner-left-edge.svg#svgClipPath");
+        --uc-tab-corner-right-side-svg: url("../icons/tab-bottom-corner-right-edge.svg");
+        --uc-tab-corner-right-side-clipPath: url("../icons/tab-bottom-corner-right-edge.svg#svgClipPath");
+        --uc-tab-corner-left-side-svg-clipped: url("../icons/tab-bottom-corner-left-edge-clipped.svg");
+        --uc-tab-corner-right-side-svg-clipped: url("../icons/tab-bottom-corner-right-edge-clipped.svg");
+        --uc-tab-corner-size: 14px;
+      }
+    }
+
+    @supports -moz-bool-pref("userChrome.tab.bottom_rounded_corner.all") {
+      .tabbrowser-tab {
+        padding-inline: 0 !important;
+        overflow-clip-margin: var(--uc-tab-corner-half-size) !important;
+      }
+      .tabbrowser-tab .tab-background {
+        --tab-border-radius: 0px;
+        margin-inline: var(--uc-tab-corner-half-size) !important;
+        position: relative;
+      }
+    }
+    @supports not -moz-bool-pref("userChrome.tab.bottom_rounded_corner.all") {
+      .tabbrowser-tab[visuallyselected] {
+        padding-inline: 0 !important;
+        overflow-clip-margin: var(--uc-tab-corner-half-size) !important;
+      }
+      .tabbrowser-tab[visuallyselected] .tab-background {
+        --tab-border-radius: 0px;
+        margin-inline: var(--uc-tab-corner-half-size) !important;
+        position: relative;
+      }
+      .tabbrowser-tab[visuallyselected] .tab-background::before,
+      .tabbrowser-tab[visuallyselected] .tab-background::after {
+        content: "";
+      }
+    }
+    .tabbrowser-tab .tab-background::before,
+    .tabbrowser-tab .tab-background::after {
+      /* Box */
+      display: block;
+      position: absolute;
+      z-index: -1;
+      bottom: 0;
+      /* Shape */
+      width: var(--uc-tab-corner-size);
+      height: var(--uc-tab-corner-height);
+      /* Color */
+      fill: transparent;
       stroke: transparent;
+      -moz-context-properties: fill, stroke, stroke-opacity;
+      /* Image */
+      background-size: cover, auto auto;
+      background-repeat: no-repeat, no-repeat;
+      background-position: bottom, right top;
+      background-attachment: scroll, fixed;
+    }
+    @supports -moz-bool-pref("userChrome.tab.bottom_rounded_corner.all") {
+      .tabbrowser-tab .tab-background::before,
+      .tabbrowser-tab .tab-background::after {
+        content: "";
+      }
+    }
+    @supports not -moz-bool-pref("userChrome.tab.color_like_toolbar") {
+      .tabbrowser-tab .tab-background::before,
+      .tabbrowser-tab .tab-background::after {
+        /* Based on tab background
+             background-image: linear-gradient(var(--lwt-selected-tab-background-color, transparent), var(--lwt-selected-tab-background-color, transparent)), linear-gradient(var(--toolbar-bgcolor), var(--toolbar-bgcolor)), var(--lwt-header-image, none);
+
+             defaults
+             background-color: var(--tab-selected-bgcolor, var(--toolbar-bgcolor));
+             background-image: var(--tab-selected-bgimage, var(--toolbar-bgimage));
+        */
+        fill: var(--lwt-selected-tab-background-color, var(--tab-selected-bgcolor, var(--toolbar-bgcolor))) !important;
+      }
+    }
+    .tabbrowser-tab .tab-background::before {
+      right: 100%;
+      background-image: var(--uc-tab-corner-left-side-svg), var(--uc-tab-corner-bgimage);
+      clip-path: var(--uc-tab-corner-left-side-clipPath);
+    }
+    .tabbrowser-tab .tab-background::after {
+      left: 100%;
+      background-image: var(--uc-tab-corner-right-side-svg), var(--uc-tab-corner-bgimage);
+      clip-path: var(--uc-tab-corner-right-side-clipPath);
+    }
+    .tabbrowser-tab[beforeselected-visible] .tab-background::after {
+      --uc-tab-corner-right-side-svg: var(--uc-tab-corner-right-side-svg-clipped);
+    }
+    .tabbrowser-tab[visuallyselected] + .tabbrowser-tab .tab-background::before {
+      --uc-tab-corner-left-side-svg: var(--uc-tab-corner-left-side-svg-clipped);
+    }
+    .tabbrowser-tab:is([visuallyselected], [multiselected]) .tab-background {
+      --uc-tab-corner-bgimage: var(--lwt-header-image, none);
+    }
+    .tabbrowser-tab:is([visuallyselected], [multiselected]) .tab-background::before,
+    .tabbrowser-tab:is([visuallyselected], [multiselected]) .tab-background::after {
+      fill: var(--tab-selected-bgcolor, var(--toolbar-bgcolor));
+    }
+    @supports -moz-bool-pref("userChrome.tab.box_shadow") {
+      .tabbrowser-tab:is([visuallyselected], [multiselected]) .tab-background::before,
+      .tabbrowser-tab:is([visuallyselected], [multiselected]) .tab-background::after {
+        stroke: var(--uc-tab-shadow-color);
+      }
+    }
+    .tabbrowser-tab:hover:not([visuallyselected], [multiselected]) .tab-background::before,
+    .tabbrowser-tab:hover:not([visuallyselected], [multiselected]) .tab-background::after {
+      fill: color-mix(in srgb, currentColor 11%, transparent);
+    }
+
+    @supports -moz-bool-pref("userChrome.tab.multi_selected") {
+      .tabbrowser-tab[multiselected]:not([visuallyselected]) .tab-background::before,
+      .tabbrowser-tab[multiselected]:not([visuallyselected]) .tab-background::after {
+        fill: var(--uc-multiselected-tab-bgcolor);
+      }
+    }
+    #tabbrowser-tabs[movingtab] .tabbrowser-tab:is([visuallyselected], [multiselected]) .tab-background:-moz-lwtheme {
+      --uc-tab-corner-bgimage: none;
+    }
+
+    @supports -moz-bool-pref("userChrome.tab.box_shadow") {
+      :root:is([lwtheme-mozlightdark], [style*="--lwt-accent-color: rgb(240, 240, 244); --lwt-text-color: rgba(21, 20, 26);"], [style*="--lwt-accent-color: rgb(28, 27, 34); --lwt-text-color: rgba(251, 251, 254);"])
+        #TabsToolbar[brighttext]
+        #tabbrowser-tabs:not([noshadowfortests])
+        .tabbrowser-tab:is([visuallyselected], [multiselected])
+        .tab-background::before,
+      :root:is([lwtheme-mozlightdark], [style*="--lwt-accent-color: rgb(240, 240, 244); --lwt-text-color: rgba(21, 20, 26);"], [style*="--lwt-accent-color: rgb(28, 27, 34); --lwt-text-color: rgba(251, 251, 254);"])
+        #TabsToolbar[brighttext]
+        #tabbrowser-tabs:not([noshadowfortests])
+        .tabbrowser-tab:is([visuallyselected], [multiselected])
+        .tab-background::after {
+        stroke-opacity: 0.3;
+      }
+    }
+    @media (-moz-gtk-csd-available) {
+      :root {
+        /* Fill color for GTK */
+      }
+      @supports -moz-bool-pref("userChrome.tab.box_shadow") {
+        :root:not([lwtheme="true"]) .tabbrowser-tab {
+          --uc-tab-shadow-color: rgba(0, 0, 0, 0.4);
+        }
+      }
+      :root:not([lwtheme="true"]) .tabbrowser-tab[visuallyselected] .tab-background {
+        background-clip: content-box;
+      }
+      :root:not([lwtheme="true"]) .tabbrowser-tab[visuallyselected] .tab-background::before,
+      :root:not([lwtheme="true"]) .tabbrowser-tab[visuallyselected] .tab-background::after {
+        /* As GTK Toolbar's background-color + background-image
+         * --toolbar-non-lwt-bgcolor: -moz-dialog;
+         * --toolbar-non-lwt-bgimage: linear-gradient(rgba(255,255,255,.15), rgba(255,255,255,.15));
+         */
+        --uc-tab-corner-bgimage: linear-gradient(var(--toolbar-non-lwt-bgcolor), var(--toolbar-non-lwt-bgcolor));
+        fill: rgba(255, 255, 255, 0.075);
+      }
+      @supports not -moz-bool-pref("userChrome.tab.color_like_toolbar") {
+        :root:not([lwtheme="true"]) .tabbrowser-tab[visuallyselected] .tab-background::before,
+        :root:not([lwtheme="true"]) .tabbrowser-tab[visuallyselected] .tab-background::after {
+          fill: rgba(255, 255, 255, 0.15);
+        }
+      }
+    }
+
+    #tabbrowser-tabs[positionpinnedtabs],
+    #tabbrowser-tabs:not([overflow]) .tabbrowser-tab[first-visible-tab],
+    #tabbrowser-tabs[overflow] .tabbrowser-tab[first-visible-unpinned-tab] {
+      margin-left: var(--uc-tab-corner-half-size) !important;
+    }
+
+    .tabbrowser-tab[last-visible-tab] {
+      margin-right: vart(--uc-tab-corner-half-size) !important;
     }
   }
 }
@@ -7001,38 +7285,75 @@
 /*= New tab button ============================================================*/
 /*= New tab button - Looks like tab ==========================================*/
 @supports -moz-bool-pref("userChrome.tab.newtab_button_like_tab") {
-  #tabs-newtab-button {
-    /* Original:
-      margin: 0 0 var(--tabs-navbar-shadow-size) !important
-      => Can't override style. Therefore, we should approach it by bypass.
+  @supports -moz-bool-pref("userChrome.tab.connect_to_window") {
+    #tabs-newtab-button {
+      /* Size */
+      -moz-box-align: stretch !important;
+      padding-top: var(--tab-block-margin) !important;
+    }
+  }
+  @supports -moz-bool-pref("userChrome.tab.bottom_rounded_corner") {
+    #tabs-newtab-button {
+      /* Original:
+       margin: 0 0 var(--tabs-navbar-shadow-size) !important
+       => Can't override style. Therefore, we should approach it by bypass.
       */
-    --tabs-navbar-shadow-size: -1px;
-    /* Original: 1px */
-    --tabs-navbar-original-shadow-size: 0.5px;
-    --tab-corner-rounding: 4px;
-    /* Hardcoded */
-    /* Size */
-    -moz-box-align: stretch !important;
-    padding-top: var(--tab-block-margin) !important;
-    /* Corner Rounding Image */
-    --newtab-position: calc((var(--tab-corner-rounding) / 2) * -1);
-    background-image: url("../icons/tab-bottom-corner-left.svg"), url("../icons/tab-bottom-corner-right.svg");
-    background-repeat: no-repeat;
-    background-position: left var(--newtab-position) bottom var(--tabs-navbar-original-shadow-size),
-      right var(--newtab-position) bottom var(--tabs-navbar-original-shadow-size);
-    background-size: var(--tab-corner-rounding);
-    /* Corner Rounding Color */
-    fill: transparent !important;
-    -moz-context-properties: fill !important;
+      --tabs-navbar-shadow-size: -1px;
+      /* Original: 1px */
+      --uc-tabs-navbar-shadow-size: 0.5px;
+      --uc-tab-corner-rounding: 4px;
+      /* Hardcoded */
+      --uc-newtab-bgcolor: transparent;
+      /* Corner Rounding Image */
+      --uc-newtab-position: calc((var(--uc-tab-corner-rounding) / 2) * -1);
+      background-image: var(--uc-tab-corner-left-side-svg), var(--uc-tab-corner-right-side-svg);
+      background-repeat: no-repeat;
+      background-position: left var(--uc-newtab-position) bottom var(--uc-tabs-navbar-shadow-size),
+        right var(--uc-newtab-position) bottom var(--uc-tabs-navbar-shadow-size);
+      background-size: var(--uc-tab-corner-rounding);
+      /* Corner Rounding Color */
+      fill: var(--uc-newtab-bgcolor) !important;
+      -moz-context-properties: fill !important;
+    }
+    @supports -moz-bool-pref("userChrome.tab.bottom_rounded_corner.wave") or -moz-bool-pref(
+        "userChrome.tab.bottom_rounded_corner.australis"
+      ) or -moz-bool-pref("userChrome.tab.bottom_rounded_corner.chrome_legacy") or -moz-bool-pref(
+        "userChrome.tab.bottom_rounded_corner.chrome"
+      ) or -moz-bool-pref("userChrome.tab.bottom_rounded_corner.edge") {
+      #tabs-newtab-button {
+        --uc-newtab-position: 0px;
+        --uc-newtab-non-corner-bgwidth: 0px;
+        --uc-tab-corner-half-height: calc(var(--uc-tab-corner-height) / 2);
+        --uc-tab-corner-half-height-reverse: calc(var(--uc-tab-corner-half-height) * -1);
+        transform: translateX(var(--uc-tab-corner-half-height-reverse));
+        padding-inline: var(--uc-tab-corner-half-height) !important;
+        overflow-clip-margin: var(--uc-tab-corner-half-height) !important;
+        background-image: var(--uc-tab-corner-left-side-svg),
+          linear-gradient(to left, var(--uc-newtab-bgcolor), var(--uc-newtab-bgcolor)),
+          var(--uc-tab-corner-right-side-svg);
+        background-position: left var(--uc-newtab-position) bottom var(--uc-tabs-navbar-shadow-size),
+          center bottom var(--uc-tabs-navbar-shadow-size),
+          right var(--uc-newtab-position) bottom var(--uc-tabs-navbar-shadow-size);
+        background-size: var(--uc-tab-corner-height) var(--uc-tab-corner-height),
+          var(--uc-newtab-non-corner-bgwidth) var(--uc-tab-corner-height),
+          var(--uc-tab-corner-height) var(--uc-tab-corner-height);
+        background-origin: padding-box;
+      }
+      @supports -moz-bool-pref("userChrome.tab.bottom_rounded_corner.chrome") or -moz-bool-pref("userChrome.tab.bottom_rounded_corner.edge") {
+        #tabs-newtab-button {
+          --uc-newtab-non-corner-bgwidth: calc(2 * var(--toolbarbutton-inner-padding));
+        }
+      }
+    }
   }
 
   /* Corner Rounding Color */
   #tabs-newtab-button:hover {
-    fill: var(--toolbarbutton-hover-background) !important;
+    --uc-newtab-bgcolor: var(--toolbarbutton-hover-background);
   }
 
   #tabs-newtab-button:hover:active {
-    fill: var(--toolbarbutton-active-background) !important;
+    --uc-newtab-bgcolor: var(--toolbarbutton-active-background);
   }
 
   @media (-moz-windows-accent-color-in-titlebar) {
@@ -7048,6 +7369,36 @@
       /* Hardcoded for compatibility */
     }
 
+    @supports -moz-bool-pref("userChrome.tab.bottom_rounded_corner") {
+      @supports -moz-bool-pref("userChrome.tab.bottom_rounded_corner.wave") or -moz-bool-pref(
+          "userChrome.tab.bottom_rounded_corner.australis"
+        ) or -moz-bool-pref("userChrome.tab.bottom_rounded_corner.chrome_legacy") or -moz-bool-pref(
+          "userChrome.tab.bottom_rounded_corner.chrome"
+        ) or -moz-bool-pref("userChrome.tab.bottom_rounded_corner.edge") {
+        :root[tabsintitlebar]:not(:-moz-window-inactive, :-moz-lwtheme) #tabs-newtab-button:hover,
+        :root[tabsintitlebar][lwt-default-theme-in-dark-mode]:not(:-moz-window-inactive) #tabs-newtab-button:hover {
+          background-image: var(--uc-tab-corner-left-side-svg),
+            linear-gradient(
+              to left,
+              color-mix(in srgb, AccentColorText 10%, transparent),
+              color-mix(in srgb, AccentColorText 10%, transparent)
+            ),
+            var(--uc-tab-corner-right-side-svg);
+        }
+
+        :root[tabsintitlebar]:not(:-moz-window-inactive, :-moz-lwtheme) #tabs-newtab-button:hover:active,
+        :root[tabsintitlebar][lwt-default-theme-in-dark-mode]:not(:-moz-window-inactive)
+          #tabs-newtab-button:hover:active {
+          background-image: var(--uc-tab-corner-left-side-svg),
+            linear-gradient(
+              to left,
+              color-mix(in srgb, AccentColorText 15%, transparent),
+              color-mix(in srgb, AccentColorText 15%, transparent)
+            ),
+            var(--uc-tab-corner-right-side-svg);
+        }
+      }
+    }
     @supports -moz-bool-pref("userChrome.compatibility.accent_color") {
       :root[tabsintitlebar]:not(:-moz-window-inactive, :-moz-lwtheme) #tabs-newtab-button:hover,
       :root[tabsintitlebar][lwt-default-theme-in-dark-mode]:not(:-moz-window-inactive) #tabs-newtab-button:hover {
@@ -7061,6 +7412,37 @@
         fill: color-mix(in srgb, -moz-accent-color-foreground 15%, transparent) !important;
         /* Hardcoded for compatibility */
       }
+
+      @supports -moz-bool-pref("userChrome.tab.bottom_rounded_corner") {
+        @supports -moz-bool-pref("userChrome.tab.bottom_rounded_corner.wave") or -moz-bool-pref(
+            "userChrome.tab.bottom_rounded_corner.australis"
+          ) or -moz-bool-pref("userChrome.tab.bottom_rounded_corner.chrome_legacy") or -moz-bool-pref(
+            "userChrome.tab.bottom_rounded_corner.chrome"
+          ) or -moz-bool-pref("userChrome.tab.bottom_rounded_corner.edge") {
+          :root[tabsintitlebar]:not(:-moz-window-inactive, :-moz-lwtheme) #tabs-newtab-button:hover,
+          :root[tabsintitlebar][lwt-default-theme-in-dark-mode]:not(:-moz-window-inactive) #tabs-newtab-button:hover {
+            background-image: var(--uc-tab-corner-left-side-svg),
+              linear-gradient(
+                to left,
+                color-mix(in srgb, -moz-accent-color-foreground 10%, transparent),
+                color-mix(in srgb, -moz-accent-color-foreground 10%, transparent)
+              ),
+              var(--uc-tab-corner-right-side-svg);
+          }
+
+          :root[tabsintitlebar]:not(:-moz-window-inactive, :-moz-lwtheme) #tabs-newtab-button:hover:active,
+          :root[tabsintitlebar][lwt-default-theme-in-dark-mode]:not(:-moz-window-inactive)
+            #tabs-newtab-button:hover:active {
+            background-image: var(--uc-tab-corner-left-side-svg),
+              linear-gradient(
+                to left,
+                color-mix(in srgb, -moz-accent-color-foreground 15%, transparent),
+                color-mix(in srgb, -moz-accent-color-foreground 15%, transparent)
+              ),
+              var(--uc-tab-corner-right-side-svg);
+          }
+        }
+      }
     }
   }
   /* '+'Icon */
@@ -7068,11 +7450,24 @@
     border-radius: var(--tab-border-radius) var(--tab-border-radius) 0 0 !important;
     /* Original: var(--tab-border-radius) */
     padding: calc(var(--toolbarbutton-inner-padding) - var(--tab-block-margin) / 4) var(--toolbarbutton-inner-padding)
-      calc(var(--toolbarbutton-inner-padding) + var(--tab-block-margin) / 4 + var(--tabs-navbar-original-shadow-size)) !important;
+      calc(var(--toolbarbutton-inner-padding) + var(--tab-block-margin) / 4 + var(--uc-tabs-navbar-shadow-size)) !important;
     -moz-context-properties: fill, fill-opacity;
     fill: var(--toolbarbutton-icon-fill);
     fill-opacity: var(--toolbarbutton-icon-fill-opacity);
   }
+  @supports -moz-bool-pref("userChrome.tab.bottom_rounded_corner.wave") or -moz-bool-pref(
+      "userChrome.tab.bottom_rounded_corner.australis"
+    ) or -moz-bool-pref("userChrome.tab.bottom_rounded_corner.chrome_legacy") or -moz-bool-pref(
+      "userChrome.tab.bottom_rounded_corner.chrome"
+    ) or -moz-bool-pref("userChrome.tab.bottom_rounded_corner.edge") {
+    #tabs-newtab-button .toolbarbutton-icon {
+      --tab-border-radius: 0px;
+      width: unset !important;
+      padding-inline: 0px !important;
+      margin-inline: calc(var(--uc-tab-corner-half-height) - 7.75px) !important;
+      background-color: transparent !important;
+    }
+  }
 }
 /*= New tab button - Smaller button ==========================================*/
 @supports -moz-bool-pref("userChrome.tab.newtab_button_smaller") {
diff --git a/icons/tab-bottom-corner-left-australis-clipped.svg b/icons/tab-bottom-corner-left-australis-clipped.svg
new file mode 100644
index 00000000..6467247b
--- /dev/null
+++ b/icons/tab-bottom-corner-left-australis-clipped.svg
@@ -0,0 +1,3 @@
+<svg width="30" height="30" viewBox="0 0 30 30" xmlns="http://www.w3.org/2000/svg">
+  <path fill="context-fill" stroke="context-stroke" stroke-opacity="context-stroke-opacity" stroke-width="1.5" stroke-dasharray="47.7, 100" d="M30 0h-1.5C20.286.018 16.736 3.745 15 7.967l.045.105c.18.447.342.9.486 1.36.21.675.392 1.358.547 2.047.101.45.19.899.272 1.337.081.44.154.87.222 1.29.137.837.253 1.625.377 2.335.178 1.01.397 2.01.656 3.002.182.676.393 1.345.631 2.004a17.87 17.87 0 0 0 1.05 2.348c.29.525.612 1.03.966 1.514.344.463.722.9 1.13 1.306a10.525 10.525 0 0 0 1.79 1.414c.674.422 1.392.77 2.14 1.041a15.082 15.082 0 0 0 2.523.673c.47.083.942.148 1.417.195.245.024.494.045.748.062V0"/>
+</svg>
diff --git a/icons/tab-bottom-corner-left-australis.svg b/icons/tab-bottom-corner-left-australis.svg
new file mode 100644
index 00000000..955e3903
--- /dev/null
+++ b/icons/tab-bottom-corner-left-australis.svg
@@ -0,0 +1,9 @@
+<svg width="30" height="30" viewBox="0 0 30 30" xmlns="http://www.w3.org/2000/svg">
+  <defs>
+    <path id="tabCorner" fill="context-fill" stroke="context-stroke" stroke-opacity="context-stroke-opacity" stroke-width="1.5" stroke-dasharray="46.5, 100" d="M28.5 0C14.55.03 14.046 10.757 13.05 16.442 11.56 24.942 8.125 29.452 0 30h30V0m0 0h-1.5"/>
+  </defs>
+  <clipPath id="svgClipPath" clipPathUnits="objectBoundingBox">
+    <use href="#tabCorner" x="-2.2" transform="scale(0.036, 0.0333)" />
+  </clipPath>
+  <use href="#tabCorner" />
+</svg>
diff --git a/icons/tab-bottom-corner-left-chrome-clipped.svg b/icons/tab-bottom-corner-left-chrome-clipped.svg
new file mode 100644
index 00000000..24ae50b3
--- /dev/null
+++ b/icons/tab-bottom-corner-left-chrome-clipped.svg
@@ -0,0 +1,3 @@
+<svg width="18" height="36" viewBox="0 0 18 36" xmlns="http://www.w3.org/2000/svg">
+  <path fill="context-fill" stroke="context-stroke" stroke-opacity="context-stroke-opacity" stroke-width="1.5" stroke-dasharray="47 100" d="M18 0a9 9 0 0 0-7.571 4.135 9 9 0 0 0-.617 1.127 9 9 0 0 0-.72 2.457A9 9 0 0 0 9 9v18a9 9 0 0 0 4.135 7.571 9 9 0 0 0 1.127.617 9 9 0 0 0 2.457.72A9 9 0 0 0 18 36V0"/>
+</svg>
diff --git a/icons/tab-bottom-corner-left-chrome.svg b/icons/tab-bottom-corner-left-chrome.svg
new file mode 100644
index 00000000..fda2f96f
--- /dev/null
+++ b/icons/tab-bottom-corner-left-chrome.svg
@@ -0,0 +1,9 @@
+<svg width="18" height="36" viewBox="0 0 18 36" xmlns="http://www.w3.org/2000/svg">
+  <defs>
+    <path id="tabCorner" fill="context-fill" stroke="context-stroke" stroke-opacity="context-stroke-opacity" stroke-width="1.5" stroke-dasharray="47 100" d="M18 0a9 9 0 0 0-7.571 4.135 9 9 0 0 0-.617 1.127 9 9 0 0 0-.72 2.457A9 9 0 0 0 9 9v18a9 9 0 0 1-4.135 7.571 9 9 0 0 1-1.127.617 9 9 0 0 1-2.457.72A9 9 0 0 1 0 36h18V0"/>
+  </defs>
+  <clipPath id="svgClipPath" clipPathUnits="objectBoundingBox">
+    <use href="#tabCorner" x="-2.5" transform="scale(0.065, 0.0277)" />
+  </clipPath>
+  <use href="#tabCorner" />
+</svg>
diff --git a/icons/tab-bottom-corner-left-chromeLegacy-clipped.svg b/icons/tab-bottom-corner-left-chromeLegacy-clipped.svg
new file mode 100644
index 00000000..da5e1b84
--- /dev/null
+++ b/icons/tab-bottom-corner-left-chromeLegacy-clipped.svg
@@ -0,0 +1,3 @@
+<svg width="36" height="36" viewBox="0 0 36 36" xmlns="http://www.w3.org/2000/svg">
+  <path fill="context-fill" stroke="context-stroke" stroke-opacity="context-stroke-opacity" stroke-width="1.5" stroke-dasharray="59 100" d="M36 0h-9l-9 18 9 18h9V0"/>
+</svg>
diff --git a/icons/tab-bottom-corner-left-chromeLegacy.svg b/icons/tab-bottom-corner-left-chromeLegacy.svg
new file mode 100644
index 00000000..5b71bd85
--- /dev/null
+++ b/icons/tab-bottom-corner-left-chromeLegacy.svg
@@ -0,0 +1,9 @@
+<svg width="36" height="36" viewBox="0 0 36 36" xmlns="http://www.w3.org/2000/svg">
+  <defs>
+    <path id="tabCorner" fill="context-fill" stroke="context-stroke" stroke-opacity="context-stroke-opacity" stroke-width="1.5" stroke-dasharray="59 100" d="M0 36h9L27 0h9v36z"/>
+  </defs>
+  <clipPath id="svgClipPath" clipPathUnits="objectBoundingBox">
+    <use href="#tabCorner" x="-2.5" transform="scale(0.0299, 0.0277)" />
+  </clipPath>
+  <use href="#tabCorner" />
+</svg>
diff --git a/icons/tab-bottom-corner-left-edge-clipped.svg b/icons/tab-bottom-corner-left-edge-clipped.svg
new file mode 100644
index 00000000..e92817ee
--- /dev/null
+++ b/icons/tab-bottom-corner-left-edge-clipped.svg
@@ -0,0 +1,3 @@
+<svg width="16" height="32" viewBox="0 0 16 32" xmlns="http://www.w3.org/2000/svg">
+  <path fill="context-fill" stroke="context-stroke" stroke-opacity="context-stroke-opacity" stroke-width="1.5" stroke-dasharray="44.5, 100" d="M16 0h-4a4 4 0 0 0-3.365 1.838 4 4 0 0 0-.473 1.035A4 4 0 0 0 8 4v24a4 4 0 0 0 1.838 3.365 4 4 0 0 0 1.035.473A4 4 0 0 0 12 32h4V0"/>
+</svg>
diff --git a/icons/tab-bottom-corner-left-edge.svg b/icons/tab-bottom-corner-left-edge.svg
new file mode 100644
index 00000000..d24d02c8
--- /dev/null
+++ b/icons/tab-bottom-corner-left-edge.svg
@@ -0,0 +1,9 @@
+<svg width="16" height="32" viewBox="0 0 16 32" xmlns="http://www.w3.org/2000/svg">
+  <defs>
+    <path id="tabCorner" fill="context-fill" stroke="context-stroke" stroke-opacity="context-stroke-opacity" stroke-width="1.5" stroke-dasharray="37, 100" d="M12 0a4 4 0 0 0-3.365 1.838A4 4 0 0 0 8 4v24a4 4 0 0 1-1.38 3.023A4 4 0 0 1 4 32h12V0m0 0h-4"/>
+  </defs>
+  <clipPath id="svgClipPath" clipPathUnits="objectBoundingBox">
+    <use href="#tabCorner" x="-2.5" transform="scale(0.075, 0.0333)" />
+  </clipPath>
+  <use href="#tabCorner" />
+</svg>
diff --git a/icons/tab-bottom-corner-left-wave-clipped.svg b/icons/tab-bottom-corner-left-wave-clipped.svg
new file mode 100644
index 00000000..5d708659
--- /dev/null
+++ b/icons/tab-bottom-corner-left-wave-clipped.svg
@@ -0,0 +1,3 @@
+<svg width="36" height="36" viewBox="0 0 36 36" xmlns="http://www.w3.org/2000/svg">
+  <path fill="context-fill" stroke="context-stroke" stroke-opacity="context-stroke-opacity" stroke-width="1.5" stroke-dasharray="60, 100" d="M36 0c-6 0-12 0-15 6-1.5 3-2.25 7.5-3 12 .188 1.125.375 2.25.574 3.352.1.55.202 1.096.309 1.632.107.536.219 1.063.336 1.578.117.516.24 1.021.37 1.51.131.49.268.963.415 1.42.146.457.301.898.467 1.317a14.336 14.336 0 0 0 .818 1.736 9.98 9.98 0 0 0 1.695 2.236 9.134 9.134 0 0 0 2.498 1.754c.302.147.61.278.926.397.316.118.639.224.967.318.328.094.66.176 1 .248.34.072.685.133 1.033.186.71.102 1.423.176 2.139.222.363.024.73.042 1.098.055.368.013.739.021 1.11.027C34.5 36 35.25 36 36 36V0"/>
+</svg>
diff --git a/icons/tab-bottom-corner-left-wave.svg b/icons/tab-bottom-corner-left-wave.svg
new file mode 100644
index 00000000..32e0c1bf
--- /dev/null
+++ b/icons/tab-bottom-corner-left-wave.svg
@@ -0,0 +1,9 @@
+<svg width="36" height="36" viewBox="0 0 36 36" xmlns="http://www.w3.org/2000/svg">
+  <defs>
+    <path id="tabCorner" fill="context-fill" stroke="context-stroke" stroke-opacity="context-stroke-opacity" stroke-width="1.5" stroke-dasharray="59.75 100" d="M 0,36 C 6,36 12.001,36 15.0005,30.0005 18,24.001 18,12.001 21.0005,6.0005 24.001,0 30,0 36,0 c 0,0 0,36 0,36 0,0 -36,0 -36,0 z"/>
+  </defs>
+  <clipPath id="svgClipPath" clipPathUnits="objectBoundingBox">
+    <use href="#tabCorner" x="-2.5" transform="scale(0.0299, 0.0277)" />
+  </clipPath>
+  <use href="#tabCorner" />
+</svg>
diff --git a/icons/tab-bottom-corner-right-australis-cilpped.svg b/icons/tab-bottom-corner-right-australis-cilpped.svg
new file mode 100644
index 00000000..409e3bd3
--- /dev/null
+++ b/icons/tab-bottom-corner-right-australis-cilpped.svg
@@ -0,0 +1,3 @@
+<svg width="30" height="30" viewBox="0 0 30 30" xmlns="http://www.w3.org/2000/svg">
+  <path fill="context-fill" stroke="context-stroke" stroke-opacity="context-stroke-opacity" stroke-width="1.5" stroke-dasharray="47, 100" d="M0 0h1.5m0 0C9.714.018 13.264 3.745 15 7.967l-.045.105c-.18.447-.342.9-.486 1.36a26.38 26.38 0 0 0-.547 2.047c-.101.45-.19.899-.272 1.337-.08.44-.154.87-.222 1.29-.137.837-.253 1.625-.377 2.335a38.38 38.38 0 0 1-.305 1.547c-.109.5-.225.986-.351 1.455a25.149 25.149 0 0 1-.631 2.004 17.918 17.918 0 0 1-1.05 2.348 14.16 14.16 0 0 1-.966 1.514c-.344.463-.722.9-1.13 1.306a10.525 10.525 0 0 1-1.79 1.414c-.674.422-1.392.77-2.14 1.041a13.21 13.21 0 0 1-1.213.383c-.432.116-.87.212-1.31.29-.47.083-.942.148-1.417.195-.245.024-.494.045-.748.062V0"/>
+</svg>
diff --git a/icons/tab-bottom-corner-right-australis.svg b/icons/tab-bottom-corner-right-australis.svg
new file mode 100644
index 00000000..aef6e0e4
--- /dev/null
+++ b/icons/tab-bottom-corner-right-australis.svg
@@ -0,0 +1,9 @@
+<svg width="30" height="30" viewBox="0 0 30 30" xmlns="http://www.w3.org/2000/svg">
+  <defs>
+    <path id="tabCorner" fill="context-fill" stroke="context-stroke" stroke-opacity="context-stroke-opacity" stroke-width="1.5" stroke-dasharray="46.5, 100" d="M0 0h1.5m0 0c13.95.03 14.454 10.757 15.45 16.442C18.44 24.942 21.875 29.452 30 30H0V0"/>
+  </defs>
+  <clipPath id="svgClipPath" clipPathUnits="objectBoundingBox">
+    <use href="#tabCorner" transform="scale(0.036, 0.0333)" />
+  </clipPath>
+  <use href="#tabCorner" />
+</svg>
diff --git a/icons/tab-bottom-corner-right-chrome-clipped.svg b/icons/tab-bottom-corner-right-chrome-clipped.svg
new file mode 100644
index 00000000..96baab91
--- /dev/null
+++ b/icons/tab-bottom-corner-right-chrome-clipped.svg
@@ -0,0 +1,3 @@
+<svg width="18" height="36" viewBox="0 0 18 36" xmlns="http://www.w3.org/2000/svg">
+  <path fill="context-fill" stroke="context-stroke" stroke-opacity="context-stroke-opacity" stroke-width="1.5" stroke-dasharray="47 100" d="M0 0a9 9 0 0 1 7.571 4.135 9 9 0 0 1 .617 1.127 9 9 0 0 1 .72 2.457A9 9 0 0 1 9 9v18a9 9 0 0 1-4.135 7.571 9 9 0 0 1-1.127.617 9 9 0 0 1-2.457.72A9 9 0 0 1 0 36V0"/>
+</svg>
diff --git a/icons/tab-bottom-corner-right-chrome.svg b/icons/tab-bottom-corner-right-chrome.svg
new file mode 100644
index 00000000..ace52062
--- /dev/null
+++ b/icons/tab-bottom-corner-right-chrome.svg
@@ -0,0 +1,9 @@
+<svg width="18" height="36" viewBox="0 0 18 36" xmlns="http://www.w3.org/2000/svg">
+  <defs>
+    <path id="tabCorner" stroke="context-stroke" stroke-opacity="context-stroke-opacity" stroke-width="1.5" stroke-dasharray="47 100" fill="context-fill" d="M0 0a9 9 0 0 1 9 9v18a9 9 0 0 0 9 9H0V0"/>
+  </defs>
+  <clipPath id="svgClipPath" clipPathUnits="objectBoundingBox">
+    <use href="#tabCorner" transform="scale(0.065, 0.0277)" />
+  </clipPath>
+  <use href="#tabCorner" />
+</svg>
diff --git a/icons/tab-bottom-corner-right-chromeLegacy-clipped.svg b/icons/tab-bottom-corner-right-chromeLegacy-clipped.svg
new file mode 100644
index 00000000..1e4b0492
--- /dev/null
+++ b/icons/tab-bottom-corner-right-chromeLegacy-clipped.svg
@@ -0,0 +1,3 @@
+<svg width="36" height="36" viewBox="0 0 36 36" xmlns="http://www.w3.org/2000/svg">
+  <path fill="context-fill" stroke="context-stroke" stroke-opacity="context-stroke-opacity" stroke-width="1.5" stroke-dasharray="59 100" d="M0 0h9l9 18-9 18H0V0"/>
+</svg>
diff --git a/icons/tab-bottom-corner-right-chromeLegacy.svg b/icons/tab-bottom-corner-right-chromeLegacy.svg
new file mode 100644
index 00000000..9749ab7e
--- /dev/null
+++ b/icons/tab-bottom-corner-right-chromeLegacy.svg
@@ -0,0 +1,9 @@
+<svg width="36" height="36" viewBox="0 0 36 36" xmlns="http://www.w3.org/2000/svg">
+  <defs>
+    <path id="tabCorner" stroke="context-stroke" stroke-opacity="context-stroke-opacity" stroke-width="1.5" stroke-dasharray="59 100" fill="context-fill" d="M36 36h-9L9 0H0v36z"/>
+  </defs>
+  <clipPath id="svgClipPath" clipPathUnits="objectBoundingBox">
+    <use href="#tabCorner" transform="scale(0.0299, 0.0277)" />
+  </clipPath>
+  <use href="#tabCorner" />
+</svg>
diff --git a/icons/tab-bottom-corner-right-edge-clipped.svg b/icons/tab-bottom-corner-right-edge-clipped.svg
new file mode 100644
index 00000000..20bde7cb
--- /dev/null
+++ b/icons/tab-bottom-corner-right-edge-clipped.svg
@@ -0,0 +1,3 @@
+<svg width="16" height="32" viewBox="0 0 16 32" xmlns="http://www.w3.org/2000/svg">
+  <path fill="context-fill" stroke="context-stroke" stroke-opacity="context-stroke-opacity" stroke-width="1.5" stroke-dasharray="44.5, 100" d="M0 0h4a4 4 0 0 1 3.365 1.838 4 4 0 0 1 .473 1.035A4 4 0 0 1 8 4v24a4 4 0 0 1-1.838 3.365 4 4 0 0 1-1.035.473A4 4 0 0 1 4 32H0V0"/>
+</svg>
diff --git a/icons/tab-bottom-corner-right-edge.svg b/icons/tab-bottom-corner-right-edge.svg
new file mode 100644
index 00000000..a9de51f0
--- /dev/null
+++ b/icons/tab-bottom-corner-right-edge.svg
@@ -0,0 +1,9 @@
+<svg width="16" height="32" viewBox="0 0 16 32" xmlns="http://www.w3.org/2000/svg">
+  <defs>
+    <path id="tabCorner" fill="context-fill" stroke="context-stroke" stroke-opacity="context-stroke-opacity" stroke-width="1.5" stroke-dasharray="37, 100" d="M4 0a4 4 0 0 1 3.365 1.838A4 4 0 0 1 8 4v24a4 4 0 0 0 1.838 3.365A4 4 0 0 0 12 32H0V0m0 0h4"/>
+  </defs>
+  <clipPath id="svgClipPath" clipPathUnits="objectBoundingBox">
+    <use href="#tabCorner" transform="scale(0.075, 0.0333)" />
+  </clipPath>
+  <use href="#tabCorner" />
+</svg>
diff --git a/icons/tab-bottom-corner-right-wave-clipped.svg b/icons/tab-bottom-corner-right-wave-clipped.svg
new file mode 100644
index 00000000..6bbb9acc
--- /dev/null
+++ b/icons/tab-bottom-corner-right-wave-clipped.svg
@@ -0,0 +1,3 @@
+<svg width="36" height="36" viewBox="0 0 36 36" xmlns="http://www.w3.org/2000/svg">
+  <path fill="context-fill" stroke="context-stroke" stroke-opacity="context-stroke-opacity" stroke-width="1.5" stroke-dasharray="60, 100" d="M0 0c6 0 12 0 15 6 1.5 3 2.25 7.5 3 12-.188 1.125-.375 2.25-.574 3.352-.1.55-.202 1.096-.309 1.632a60.698 60.698 0 0 1-.336 1.578c-.117.516-.24 1.021-.37 1.51-.131.49-.268.963-.415 1.42a21.2 21.2 0 0 1-.467 1.317 14.336 14.336 0 0 1-.818 1.736 9.98 9.98 0 0 1-1.695 2.236 9.134 9.134 0 0 1-2.498 1.754c-.302.147-.61.278-.926.397-.316.118-.639.224-.967.318-.33.094-.664.177-1 .248-.34.072-.685.133-1.033.186a27.096 27.096 0 0 1-2.139.222c-.363.024-.73.042-1.098.055-.368.013-.739.021-1.11.027C1.5 36 .75 36 0 36V0"/>
+</svg>
diff --git a/icons/tab-bottom-corner-right-wave.svg b/icons/tab-bottom-corner-right-wave.svg
new file mode 100644
index 00000000..343b26d2
--- /dev/null
+++ b/icons/tab-bottom-corner-right-wave.svg
@@ -0,0 +1,9 @@
+<svg width="36" height="36" viewBox="0 0 36 36" xmlns="http://www.w3.org/2000/svg">
+  <defs>
+    <path id="tabCorner" fill="context-fill" stroke="context-stroke" stroke-opacity="context-stroke-opacity" stroke-width="1.5" stroke-dasharray="59.75 100" d="M 36,36 C 30,36 23.999,36 20.9995,30.0005 18,24.001 18,12.001 14.9995,6.0005 11.999,0 6,0 0,0 c 0,0 0,36 0,36 0,0 36,0 36,0 z"/>
+  </defs>
+  <clipPath id="svgClipPath" clipPathUnits="objectBoundingBox">
+    <use href="#tabCorner" transform="scale(0.0299, 0.0277)" />
+  </clipPath>
+  <use href="#tabCorner" />
+</svg>
diff --git a/src/compatibility/_theme.scss b/src/compatibility/_theme.scss
index ac139078..99d713ce 100644
--- a/src/compatibility/_theme.scss
+++ b/src/compatibility/_theme.scss
@@ -116,8 +116,8 @@ menu {
 
 /* Navbar Border */
 #navigator-toolbox:-moz-lwtheme {
-  --tabs-border-color: rgba(0, 0, 0, 0.3); /* Legacy: v96 */
-  --lwt-tabs-border-color: rgba(0, 0, 0, 0.3);
+  --tabs-border-color: rgba(0, 0, 0, 0.4); /* Legacy: v96, (0, 0, 0, 0.3) -> (0, 0, 0, 0.4)  */
+  --lwt-tabs-border-color: rgba(0, 0, 0, 0.4);
 }
 
 /*= Findbar Border Color =====================================================*/
diff --git a/src/tab/_selected_tab.scss b/src/tab/_selected_tab.scss
index cf29a078..fc23332f 100644
--- a/src/tab/_selected_tab.scss
+++ b/src/tab/_selected_tab.scss
@@ -15,7 +15,26 @@
 
 /*= Selected Tab - Bottom Rounded Corner =====================================*/
 @include Option("userChrome.tab.bottom_rounded_corner") {
-  @import "selected_tab/bottom_rounded_corner";
+  @include NotOption("userChrome.tab.bottom_rounded_corner.wave") {
+    @include NotOption("userChrome.tab.bottom_rounded_corner.australis") {
+      @include NotOption("userChrome.tab.bottom_rounded_corner.chrome") {
+        @include NotOption("userChrome.tab.bottom_rounded_corner.chrome_legacy") {
+          @include NotOption("userChrome.tab.bottom_rounded_corner.edge") {
+            @import "selected_tab/bottom_rounded_corner";
+          }
+        }
+      }
+    }
+  }
+  @include Option(
+    "userChrome.tab.bottom_rounded_corner.wave",
+    "userChrome.tab.bottom_rounded_corner.australis",
+    "userChrome.tab.bottom_rounded_corner.chrome_legacy",
+    "userChrome.tab.bottom_rounded_corner.chrome",
+    "userChrome.tab.bottom_rounded_corner.edge"
+  ) {
+    @import "selected_tab/bottom_rounded_corner_others";
+  }
 }
 
 /*= Selected Tab - Photon like contextline ===================================*/
diff --git a/src/tab/newtab_button/_looks_like_tab.scss b/src/tab/newtab_button/_looks_like_tab.scss
index 9c0edccf..6f64617f 100644
--- a/src/tab/newtab_button/_looks_like_tab.scss
+++ b/src/tab/newtab_button/_looks_like_tab.scss
@@ -1,35 +1,75 @@
 #tabs-newtab-button {
-  /* Original:
+  @include Option("userChrome.tab.connect_to_window") {
+    /* Size */
+    -moz-box-align: stretch !important;
+    padding-top: var(--tab-block-margin) !important;
+  }
+
+  @include Option("userChrome.tab.bottom_rounded_corner") {
+    /* Original:
     margin: 0 0 var(--tabs-navbar-shadow-size) !important
     => Can't override style. Therefore, we should approach it by bypass.
-    */
-  --tabs-navbar-shadow-size: -1px; /* Original: 1px */
-  --tabs-navbar-original-shadow-size: 0.5px;
-  --tab-corner-rounding: 4px; /* Hardcoded */
+   */
+    --tabs-navbar-shadow-size: -1px; /* Original: 1px */
+    --uc-tabs-navbar-shadow-size: 0.5px;
+    --uc-tab-corner-rounding: 4px; /* Hardcoded */
+    --uc-newtab-bgcolor: transparent;
+
+    /* Corner Rounding Image */
+    --uc-newtab-position: calc((var(--uc-tab-corner-rounding) / 2) * -1);
+    background-image: var(--uc-tab-corner-left-side-svg), var(--uc-tab-corner-right-side-svg);
+    background-repeat: no-repeat;
+    background-position: left var(--uc-newtab-position) bottom var(--uc-tabs-navbar-shadow-size),
+                         right var(--uc-newtab-position) bottom var(--uc-tabs-navbar-shadow-size);
+    background-size: var(--uc-tab-corner-rounding);
 
-  /* Size */
-  -moz-box-align: stretch !important;
-  padding-top: var(--tab-block-margin) !important;
+    /* Corner Rounding Color */
+    fill: var(--uc-newtab-bgcolor) !important;
+    -moz-context-properties: fill !important;
 
-  /* Corner Rounding Image */
-  --newtab-position: calc((var(--tab-corner-rounding) / 2) * -1);
-  background-image: url("../icons/tab-bottom-corner-left.svg"), url("../icons/tab-bottom-corner-right.svg");
-  background-repeat: no-repeat;
-  background-position: left var(--newtab-position) bottom var(--tabs-navbar-original-shadow-size),
-    right var(--newtab-position) bottom var(--tabs-navbar-original-shadow-size);
-  background-size: var(--tab-corner-rounding);
+    @include Option(
+      "userChrome.tab.bottom_rounded_corner.wave",
+      "userChrome.tab.bottom_rounded_corner.australis",
+      "userChrome.tab.bottom_rounded_corner.chrome_legacy",
+      "userChrome.tab.bottom_rounded_corner.chrome",
+      "userChrome.tab.bottom_rounded_corner.edge"
+    ) {
+      --uc-newtab-position: 0px;
+      --uc-newtab-non-corner-bgwidth: 0px;
+      --uc-tab-corner-half-height: calc(var(--uc-tab-corner-height) / 2);
+      --uc-tab-corner-half-height-reverse: calc(var(--uc-tab-corner-half-height) * -1);
 
-  /* Corner Rounding Color */
-  fill: transparent !important;
-  -moz-context-properties: fill !important;
+      transform: translateX(var(--uc-tab-corner-half-height-reverse));
+      padding-inline: var(--uc-tab-corner-half-height) !important;
+      overflow-clip-margin: var(--uc-tab-corner-half-height) !important;
+
+      background-image: var(--uc-tab-corner-left-side-svg),
+                        linear-gradient(to left, var(--uc-newtab-bgcolor), var(--uc-newtab-bgcolor)),
+                        var(--uc-tab-corner-right-side-svg);
+      background-position: left var(--uc-newtab-position) bottom var(--uc-tabs-navbar-shadow-size),
+                           center bottom var(--uc-tabs-navbar-shadow-size),
+                           right var(--uc-newtab-position) bottom var(--uc-tabs-navbar-shadow-size);
+      background-size: var(--uc-tab-corner-height) var(--uc-tab-corner-height),
+                       var(--uc-newtab-non-corner-bgwidth) var(--uc-tab-corner-height),
+                       var(--uc-tab-corner-height) var(--uc-tab-corner-height);
+      background-origin: padding-box;
+
+      @include Option(
+        "userChrome.tab.bottom_rounded_corner.chrome",
+        "userChrome.tab.bottom_rounded_corner.edge"
+      ) {
+        --uc-newtab-non-corner-bgwidth: calc(2 * var(--toolbarbutton-inner-padding));
+      }
+    }
+  }
 }
 
 /* Corner Rounding Color */
 #tabs-newtab-button:hover {
-  fill: var(--toolbarbutton-hover-background) !important;
+  --uc-newtab-bgcolor: var(--toolbarbutton-hover-background);
 }
 #tabs-newtab-button:hover:active {
-  fill: var(--toolbarbutton-active-background) !important;
+  --uc-newtab-bgcolor: var(--toolbarbutton-active-background);
 }
 @media (-moz-windows-accent-color-in-titlebar) {
   @include AccentColor {
@@ -49,6 +89,29 @@
         transparent
       ) !important; /* Hardcoded for compatibility */
     }
+
+    @include Option("userChrome.tab.bottom_rounded_corner") {
+      @include Option(
+        "userChrome.tab.bottom_rounded_corner.wave",
+        "userChrome.tab.bottom_rounded_corner.australis",
+        "userChrome.tab.bottom_rounded_corner.chrome_legacy",
+        "userChrome.tab.bottom_rounded_corner.chrome",
+        "userChrome.tab.bottom_rounded_corner.edge"
+      ) {
+        :root[tabsintitlebar]:not(:-moz-window-inactive, :-moz-lwtheme) #tabs-newtab-button:hover,
+        :root[tabsintitlebar][lwt-default-theme-in-dark-mode]:not(:-moz-window-inactive) #tabs-newtab-button:hover {
+          background-image: var(--uc-tab-corner-left-side-svg),
+                            linear-gradient(to left, color-mix(in srgb, $accentTextColor 10%, transparent), color-mix(in srgb, $accentTextColor 10%, transparent)),
+                            var(--uc-tab-corner-right-side-svg);
+        }
+        :root[tabsintitlebar]:not(:-moz-window-inactive, :-moz-lwtheme) #tabs-newtab-button:hover:active,
+        :root[tabsintitlebar][lwt-default-theme-in-dark-mode]:not(:-moz-window-inactive) #tabs-newtab-button:hover:active {
+          background-image: var(--uc-tab-corner-left-side-svg),
+                            linear-gradient(to left, color-mix(in srgb, $accentTextColor 15%, transparent), color-mix(in srgb, $accentTextColor 15%, transparent)),
+                            var(--uc-tab-corner-right-side-svg);
+        }
+      }
+    }
   }
 }
 
@@ -57,8 +120,26 @@
   border-radius: var(--tab-border-radius) var(--tab-border-radius) 0 0 !important; /* Original: var(--tab-border-radius) */
 
   padding: calc(var(--toolbarbutton-inner-padding) - (var(--tab-block-margin) / 4)) var(--toolbarbutton-inner-padding)
-    calc(var(--toolbarbutton-inner-padding) + (var(--tab-block-margin) / 4) + var(--tabs-navbar-original-shadow-size)) !important;
+    calc(var(--toolbarbutton-inner-padding) + (var(--tab-block-margin) / 4) + var(--uc-tabs-navbar-shadow-size)) !important;
   -moz-context-properties: fill, fill-opacity;
   fill: var(--toolbarbutton-icon-fill);
   fill-opacity: var(--toolbarbutton-icon-fill-opacity);
+
+  @include Option(
+    "userChrome.tab.bottom_rounded_corner.wave",
+    "userChrome.tab.bottom_rounded_corner.australis",
+    "userChrome.tab.bottom_rounded_corner.chrome_legacy",
+    "userChrome.tab.bottom_rounded_corner.chrome",
+    "userChrome.tab.bottom_rounded_corner.edge"
+  ) {
+    --tab-border-radius: 0px;
+    width: unset !important;
+    padding-inline: 0px !important;
+    margin-inline: calc(var(--uc-tab-corner-half-height) - #{( 15.5px / 2 )}) !important;
+
+    background-color: transparent !important;
+    // background-size: calc((var(--toolbarbutton-inner-padding) * 2 + 16px) - var(--uc-tab-corner-size)) 100%;
+    // background-repeat: no-repeat;
+    // background-position: center;
+  }
 }
diff --git a/src/tab/selected_tab/_bottom_rounded_corner.scss b/src/tab/selected_tab/_bottom_rounded_corner.scss
index 6cb2fcf6..33c396fa 100644
--- a/src/tab/selected_tab/_bottom_rounded_corner.scss
+++ b/src/tab/selected_tab/_bottom_rounded_corner.scss
@@ -1,7 +1,10 @@
-#tabbrowser-tabs {
-  --tab-corner-rounding: 3px; /* 10px looks about like chromium - 17px looks close to Australis tabs */
-  --tab-corner-padding: 0px;
-  --tab-corner-position: calc(var(--tab-corner-padding) - var(--tab-corner-rounding));
+#TabsToolbar {
+  --uc-tab-corner-rounding: 3px; /* 10px looks about like chromium - 17px looks close to Australis tabs */
+  --uc-tab-corner-padding: 0px;
+  --uc-tab-corner-position: calc(var(--uc-tab-corner-padding) - var(--uc-tab-corner-rounding));
+
+  --uc-tab-corner-left-side-svg: url("../icons/tab-bottom-corner-left.svg");
+  --uc-tab-corner-right-side-svg: url("../icons/tab-bottom-corner-right.svg");
 }
 
 :root:not([customizing="true"]) {
@@ -16,7 +19,7 @@
         bottom: 0;
 
         /* Shape */
-        width: var(--tab-corner-rounding);
+        width: var(--uc-tab-corner-rounding);
         height: 100%;
 
         /* Color */
@@ -25,7 +28,7 @@
         -moz-context-properties: fill, stroke;
 
         /* Image */
-        background-size: var(--tab-corner-rounding);
+        background-size: var(--uc-tab-corner-rounding);
         background-repeat: no-repeat;
         background-position-y: bottom;
 
@@ -45,12 +48,12 @@
       }
 
       &::before {
-        left: var(--tab-corner-position);
-        background-image: url("../icons/tab-bottom-corner-left.svg");
+        left: var(--uc-tab-corner-position);
+        background-image: var(--uc-tab-corner-left-side-svg);
       }
       &::after {
-        right: var(--tab-corner-position);
-        background-image: url("../icons/tab-bottom-corner-right.svg");
+        right: var(--uc-tab-corner-position);
+        background-image: var(--uc-tab-corner-right-side-svg);
       }
     }
 
diff --git a/src/tab/selected_tab/_bottom_rounded_corner_others.scss b/src/tab/selected_tab/_bottom_rounded_corner_others.scss
new file mode 100644
index 00000000..c8d7a113
--- /dev/null
+++ b/src/tab/selected_tab/_bottom_rounded_corner_others.scss
@@ -0,0 +1,250 @@
+//-- Mixin ---------------------------------------------------------------------
+@function _clipPathURL($svg) {
+  @return url($svg + "#svgClipPath");
+}
+@mixin _clipPath($svg, $position) {
+  $result: _clipPathURL($svg);
+
+  @if $position == "left" {
+    --uc-tab-corner-left-side-svg: #{ url($svg) };
+    --uc-tab-corner-left-side-clipPath: #{ $result };
+  }
+  @else if $position == "right" {
+    --uc-tab-corner-right-side-svg: #{ url($svg) };
+    --uc-tab-corner-right-side-clipPath: #{ $result };
+  }
+}
+@mixin _tabCornerSVG($left, $right) {
+  @include _clipPath($left,  "left" );
+  @include _clipPath($right, "right");
+}
+
+@mixin _bottomRoundedCornerOtherPadding() {
+  padding-inline: 0 !important;
+  overflow-clip-margin: var(--uc-tab-corner-half-size) !important;
+
+  .tab-background {
+    --tab-border-radius: 0px;
+    margin-inline: var(--uc-tab-corner-half-size) !important;
+    position: relative;
+
+    @content;
+  }
+}
+
+//------------------------------------------------------------------------------
+
+#TabsToolbar {
+  --uc-tab-corner-height: calc(var(--tab-min-height) + 1px);
+  --uc-tab-corner-size: var(--uc-tab-corner-height);
+  --uc-tab-corner-half-size: calc(var(--uc-tab-corner-size) / 2);
+  --uc-tab-corner-half-size-reverse: calc(var(--uc-tab-corner-half-size) * -1);
+
+  --uc-tab-corner-bgimage: none;
+
+  @include Option("userChrome.tab.bottom_rounded_corner.wave") {
+    @include _tabCornerSVG(
+      "../icons/tab-bottom-corner-left-wave.svg",
+      "../icons/tab-bottom-corner-right-wave.svg"
+    );
+    --uc-tab-corner-left-side-svg-clipped: url("../icons/tab-bottom-corner-left-wave-clipped.svg");
+    --uc-tab-corner-right-side-svg-clipped: url("../icons/tab-bottom-corner-right-wave-clipped.svg");
+  }
+  @include Option("userChrome.tab.bottom_rounded_corner.australis") {
+    @include _tabCornerSVG(
+      "../icons/tab-bottom-corner-left-australis.svg",
+      "../icons/tab-bottom-corner-right-australis.svg"
+    );
+    --uc-tab-corner-left-side-svg-clipped: url("../icons/tab-bottom-corner-left-australis-clipped.svg");
+    --uc-tab-corner-right-side-svg-clipped: url("../icons/tab-bottom-corner-right-australis-cilpped.svg");
+  }
+  @include Option("userChrome.tab.bottom_rounded_corner.chrome") {
+    @include _tabCornerSVG(
+      "../icons/tab-bottom-corner-left-chrome.svg",
+      "../icons/tab-bottom-corner-right-chrome.svg"
+    );
+    --uc-tab-corner-left-side-svg-clipped: url("../icons/tab-bottom-corner-left-chrome-clipped.svg");
+    --uc-tab-corner-right-side-svg-clipped: url("../icons/tab-bottom-corner-right-chrome-clipped.svg");
+
+    --uc-tab-corner-size: 16px; // 18px;
+  }
+  @include Option("userChrome.tab.bottom_rounded_corner.chrome_legacy") {
+    @include _tabCornerSVG(
+      "../icons/tab-bottom-corner-left-chromeLegacy.svg",
+      "../icons/tab-bottom-corner-right-chromeLegacy.svg"
+    );
+    --uc-tab-corner-left-side-svg-clipped: url("../icons/tab-bottom-corner-left-chromeLegacy-clipped.svg");
+    --uc-tab-corner-right-side-svg-clipped: url("../icons/tab-bottom-corner-right-chromeLegacy-clipped.svg");
+  }
+  @include Option("userChrome.tab.bottom_rounded_corner.edge") {
+    @include _tabCornerSVG(
+      "../icons/tab-bottom-corner-left-edge.svg",
+      "../icons/tab-bottom-corner-right-edge.svg"
+    );
+    --uc-tab-corner-left-side-svg-clipped: url("../icons/tab-bottom-corner-left-edge-clipped.svg");
+    --uc-tab-corner-right-side-svg-clipped: url("../icons/tab-bottom-corner-right-edge-clipped.svg");
+
+    --uc-tab-corner-size: 14px;
+  }
+}
+
+.tabbrowser-tab {
+  @include Option("userChrome.tab.bottom_rounded_corner.all") {
+    @include _bottomRoundedCornerOtherPadding;
+  }
+  @include NotOption("userChrome.tab.bottom_rounded_corner.all") {
+    &[visuallyselected] {
+      @include _bottomRoundedCornerOtherPadding {
+        &::before,
+        &::after {
+          content: "";
+        }
+      }
+    }
+  }
+
+  .tab-background {
+    &::before,
+    &::after {
+      /* Box */
+      display: block;
+      position: absolute;
+      z-index: -1;
+      bottom: 0;
+
+      /* Shape */
+      width: var(--uc-tab-corner-size);
+      height: var(--uc-tab-corner-height);
+
+      /* Color */
+      fill: transparent;
+      stroke: transparent;
+      -moz-context-properties: fill, stroke, stroke-opacity;
+      // For stroke
+      // box-shadow: 0 0 4px rgba(0,0,0,.4);
+      // box-shadow: 0 0 1px var(--toolbar-color) !important;
+      // box-shadow: 0 0 1px var(--tab-line-color, var(--lwt-tab-line-color, rgba(128, 128, 142, 0.9))) !important
+
+      /* Image */
+      // background-size: var(--tab-corner-rounding);
+      background-size: cover, auto auto;
+      background-repeat: no-repeat, no-repeat;
+      background-position: bottom, right top;
+      background-attachment: scroll, fixed;
+
+      @include Option("userChrome.tab.bottom_rounded_corner.all") {
+        content: "";
+      }
+      @include NotOption("userChrome.tab.color_like_toolbar") {
+        /* Based on tab background
+            background-image: linear-gradient(var(--lwt-selected-tab-background-color, transparent), var(--lwt-selected-tab-background-color, transparent)), linear-gradient(var(--toolbar-bgcolor), var(--toolbar-bgcolor)), var(--lwt-header-image, none);
+
+            defaults
+            background-color: var(--tab-selected-bgcolor, var(--toolbar-bgcolor));
+            background-image: var(--tab-selected-bgimage, var(--toolbar-bgimage));
+       */
+        fill: var(--lwt-selected-tab-background-color, var(--tab-selected-bgcolor, var(--toolbar-bgcolor))) !important;
+      }
+    }
+    &::before {
+      right: 100%;
+      background-image: var(--uc-tab-corner-left-side-svg), var(--uc-tab-corner-bgimage);
+      clip-path: var(--uc-tab-corner-left-side-clipPath);
+    }
+    &::after {
+      left: 100%;
+      background-image: var(--uc-tab-corner-right-side-svg), var(--uc-tab-corner-bgimage);
+      clip-path: var(--uc-tab-corner-right-side-clipPath);
+    }
+  }
+
+  &[beforeselected-visible] .tab-background::after {
+    --uc-tab-corner-right-side-svg: var(--uc-tab-corner-right-side-svg-clipped);
+  }
+  &[visuallyselected] + .tabbrowser-tab .tab-background::before {
+    --uc-tab-corner-left-side-svg: var(--uc-tab-corner-left-side-svg-clipped);
+  }
+  // &[positionpinnedtabs] .tabbrowser-tab[first-visible-unpinned-tab] .tab-background::before {
+  //   background-image: var(--uc-tab-corner-left-side-svg), var(--lwt-header-image, none) !important;
+  // }
+
+  &:is([visuallyselected], [multiselected]) .tab-background {
+    --uc-tab-corner-bgimage: var(--lwt-header-image, none);
+
+    &::before,
+    &::after {
+      fill: var(--tab-selected-bgcolor, var(--toolbar-bgcolor));
+
+      @include Option("userChrome.tab.box_shadow") {
+        stroke: var(--uc-tab-shadow-color);
+      }
+    }
+  }
+  &:hover:not([visuallyselected], [multiselected]) .tab-background {
+    &::before,
+    &::after {
+      fill: color-mix(in srgb, currentColor 11%, transparent);
+    }
+  }
+}
+@include Option("userChrome.tab.multi_selected") {
+  .tabbrowser-tab[multiselected]:not([visuallyselected]) .tab-background {
+    &::before,
+    &::after {
+      fill: var(--uc-multiselected-tab-bgcolor);
+    }
+  }
+}
+#tabbrowser-tabs[movingtab] .tabbrowser-tab:is([visuallyselected], [multiselected]) .tab-background:-moz-lwtheme {
+  --uc-tab-corner-bgimage: none;
+}
+
+:root {
+  &:is(
+    [lwtheme-mozlightdark],
+    [style*="--lwt-accent-color: rgb(240, 240, 244); --lwt-text-color: rgba(21, 20, 26);"],
+    [style*="--lwt-accent-color: rgb(28, 27, 34); --lwt-text-color: rgba(251, 251, 254);"]
+  ) #TabsToolbar[brighttext] #tabbrowser-tabs:not([noshadowfortests]) .tabbrowser-tab:is([visuallyselected], [multiselected]) .tab-background {
+    @include Option("userChrome.tab.box_shadow") {
+      &::before,
+      &::after {
+        stroke-opacity: 0.3;
+      }
+    }
+  }
+  @include OS($linux) {
+    /* Fill color for GTK */
+    &:not([lwtheme="true"]) .tabbrowser-tab {
+      @include Option("userChrome.tab.box_shadow") {
+        --uc-tab-shadow-color: rgba(0,0,0, 0.4);
+      }
+      &[visuallyselected] .tab-background {
+        background-clip: content-box;
+
+        &::before,
+        &::after {
+          /* As GTK Toolbar's background-color + background-image
+           * --toolbar-non-lwt-bgcolor: -moz-dialog;
+           * --toolbar-non-lwt-bgimage: linear-gradient(rgba(255,255,255,.15), rgba(255,255,255,.15));
+           */
+          --uc-tab-corner-bgimage: linear-gradient(var(--toolbar-non-lwt-bgcolor), var(--toolbar-non-lwt-bgcolor));
+          fill: rgba(255, 255, 255, .075);
+          @include NotOption("userChrome.tab.color_like_toolbar") {
+            fill: rgba(255, 255, 255, .15);
+          }
+        }
+      }
+    }
+  }
+}
+
+#tabbrowser-tabs {
+  &[positionpinnedtabs],
+  &:not([overflow]) .tabbrowser-tab[first-visible-tab],
+  &[overflow] .tabbrowser-tab[first-visible-unpinned-tab] {
+    margin-left: var(--uc-tab-corner-half-size) !important;
+  }
+}
+.tabbrowser-tab[last-visible-tab] {
+  margin-right: vart(--uc-tab-corner-half-size) !important;
+}
diff --git a/src/tab/selected_tab/_box_shadow.scss b/src/tab/selected_tab/_box_shadow.scss
index 1c29fc7f..642c700c 100644
--- a/src/tab/selected_tab/_box_shadow.scss
+++ b/src/tab/selected_tab/_box_shadow.scss
@@ -1,36 +1,58 @@
-#TabsToolbar[brighttext]
-  #tabbrowser-tabs:not([noshadowfortests])
-  .tabbrowser-tab[visuallyselected="true"]:not(:focus)
-  > .tab-stack
-  > .tab-background:-moz-lwtheme {
-  /* Original: 0 0 1px var(--tab-line-color, rgba(128,128,142,0.9))
-       Bright: 0 0 1px var(--tab-line-color, rgba(128,128,142,0.9)), 0 0 4px rgba(128,128,142,0.5) */
-  box-shadow: 0 0 1px var(--toolbar-color) !important;
+#TabsToolbar {
+  --uc-tab-background-shadow-soft: 0 0 1px;
+  --uc-tab-background-shadow-hard: 0 0 0 1px;
+  --uc-tab-shadow-color: var(--tab-line-color, var(--lwt-tab-line-color, var(--tabs-border-color, rgba(128, 128, 142, 0.9))));
+  --uc-tab-shadow-color-bundle: var(--tab-line-color, var(--lwt-tab-line-color, rgba(128, 128, 142, 0.9)));
+  --uc-tab-basic-shadow: 0 0 4px rgba(0,0,0, 0.4);
+  --uc-tab-additional-shadow: 0 0 4px rgba(128, 128, 142, 0.5);
+
+  @include Option("userChrome.tab.bottom_rounded_corner") {
+    @include Option(
+      "userChrome.tab.bottom_rounded_corner.wave",
+      "userChrome.tab.bottom_rounded_corner.australis",
+      "userChrome.tab.bottom_rounded_corner.chrome_legacy",
+      "userChrome.tab.bottom_rounded_corner.chrome",
+      "userChrome.tab.bottom_rounded_corner.edge"
+    ) {
+      // --uc-tab-background-shadow-soft: 0 -1px 1px -1px;
+      --uc-tab-background-shadow-hard: 0 -1px 0;
+      --uc-tab-basic-shadow: 0 -1px 0px rgba(0,0,0, 0.4);
+      --uc-tab-additional-shadow: 0 0 0 transparent;
+    }
+  }
 }
-#TabsToolbar[brighttext]
-  #tabbrowser-tabs:not([noshadowfortests])
-  .tabbrowser-tab[multiselected]:not([visuallyselected])
-  > .tab-stack
-  > .tab-background:-moz-lwtheme {
-  box-shadow: 0 0 1px color-mix(in srgb, var(--toolbar-color) 80%, transparent) !important;
+
+#tabbrowser-tabs:not([noshadowfortests]) .tab-background:is([selected], [multiselected]) {
+  box-shadow: var(--uc-tab-basic-shadow) !important;
 }
 
-/* Consider 0 0 4px rgba(128,128,142,0.9) -> 0 0 4px rgba(0,0,0,.4) new default */
-#TabsToolbar:not([brighttext])
-  #tabbrowser-tabs:not([noshadowfortests])
-  .tabbrowser-tab:is([visuallyselected="true"], [multiselected])
-  > .tab-stack
-  > .tab-background {
-  box-shadow: 0 0 1px var(--tab-line-color, var(--lwt-tab-line-color, rgba(128, 128, 142, 0.9))),
-    0 0 4px rgba(128, 128, 142, 0.5) !important;
+:root:is([lwtheme-mozlightdark], [style*="--lwt-accent-color: rgb(28, 27, 34); --lwt-text-color: rgba(251, 251, 254);"])
+  #TabsToolbar[brighttext] #tabbrowser-tabs:not([noshadowfortests]) .tabbrowser-tab {
+  &:is([selected], [multiselected]) {
+    > .tab-stack
+    > .tab-background:-moz-lwtheme {
+      box-shadow: var(--uc-tab-background-shadow-soft) var(--uc-tab-shadow-color) !important;
+    }
+  }
+
+  /* Original: 0 0 1px var(--tab-line-color, rgba(128,128,142,0.9))
+       Bright: 0 0 1px var(--tab-line-color, rgba(128,128,142,0.9)), 0 0 4px rgba(128,128,142,0.5) */
+  /* Consider 0 0 4px rgba(128,128,142,0.9) -> 0 0 4px rgba(0,0,0,.4) new default */
+  &[visuallyselected="true"]:not(:focus),
+  &[multiselected]:not([visuallyselected]) {
+    --uc-tab-shadow-color: var(--toolbar-color);
+  }
 }
 
-#TabsToolbar[brighttext]
+:root:is([lwtheme-mozlightdark], [style*="--lwt-accent-color: rgb(240, 240, 244); --lwt-text-color: rgba(21, 20, 26);"])
+  #TabsToolbar:not([brighttext])
   #tabbrowser-tabs:not([noshadowfortests])
-  .tabbrowser-tab:is([visuallyselected="true"], [multiselected])
+  .tabbrowser-tab:is([visuallyselected], [multiselected])
   > .tab-stack
-  > .tab-background:-moz-lwtheme {
-  box-shadow: 0 0 1px var(--tab-line-color, var(--lwt-tab-line-color, rgba(128, 128, 142, 0.9))) !important;
+  > .tab-background {
+  --uc-tab-shadow-color: var(--uc-tab-shadow-color-bundle);
+  box-shadow: var(--uc-tab-background-shadow-soft) var(--uc-tab-shadow-color),
+    var(--uc-tab-additional-shadow) !important;
 }
 
 /* For themes outside of Light and Dark (which are curated by Mozilla), show a thicker border
@@ -41,9 +63,8 @@
   .tabbrowser-tab:is([visuallyselected="true"], [multiselected])
   > .tab-stack
   > .tab-background:-moz-lwtheme {
-  box-shadow: 0 0 0 1px
-      var(--tab-line-color, var(--lwt-tab-line-color, var(--tabs-border-color, rgba(128, 128, 142, 0.9)))),
-    0 0 4px rgba(128, 128, 142, 0.5) !important;
+  box-shadow: var(--uc-tab-background-shadow-hard) var(--uc-tab-shadow-color),
+    var(--uc-tab-additional-shadow) !important;
 }
 
 :root:not([lwtheme-mozlightdark], [style*="--lwt-accent-color: rgb(28, 27, 34); --lwt-text-color: rgba(251, 251, 254);"])
@@ -52,6 +73,5 @@
   .tabbrowser-tab:is([visuallyselected="true"], [multiselected])
   > .tab-stack
   > .tab-background:-moz-lwtheme {
-  box-shadow: 0 0 0 1px
-    var(--tab-line-color, var(--lwt-tab-line-color, var(--tabs-border-color, rgba(128, 128, 142, 0.9)))) !important;
+  box-shadow: var(--uc-tab-background-shadow-hard) var(--uc-tab-shadow-color) !important;
 }
diff --git a/src/tab/selected_tab/_multi_selected.scss b/src/tab/selected_tab/_multi_selected.scss
index 12c93c4d..225d5c34 100644
--- a/src/tab/selected_tab/_multi_selected.scss
+++ b/src/tab/selected_tab/_multi_selected.scss
@@ -1,23 +1,38 @@
- #tabbrowser-tabs:not([movingtab])
+#TabsToolbar {
+  --uc-multiselected-tab-bgcolor: color-mix(in srgb, currentColor 28%, var(--toolbar-bgcolor, transparent));
+
+  &[brighttext] {
+    --uc-multiselected-tab-bgcolor: color-mix(in srgb, currentColor 16%, var(--toolbar-bgcolor, transparent));
+  }
+}
+
+#tabbrowser-tabs:not([movingtab])
   > #tabbrowser-arrowscrollbox
   > .tabbrowser-tab
   > .tab-stack
-  > .tab-background[multiselected]:not([selected]):-moz-lwtheme {
-  background-image: linear-gradient(var(--toolbar-bgcolor, transparent), var(--toolbar-bgcolor, transparent)),
-    linear-gradient(var(--toolbar-bgcolor), var(--toolbar-bgcolor)), var(--lwt-header-image, none) !important;
-}
+  > .tab-background[multiselected]:not([selected]) {
+   /* Original:
+   background-attachment: scroll, scroll, fixed;
+   background-color: transparent;
+   background-image: linear-gradient(var(--lwt-selected-tab-background-color, transparent), var(--lwt-selected-tab-background-color, transparent)),
+                     linear-gradient(var(--toolbar-bgcolor), var(--toolbar-bgcolor)),
+                     var(--lwt-header-image, none);
+   background-position: 0 0, 0 0, right top;
+   background-repeat: repeat-x, repeat-x, no-repeat;
+   background-size: auto 100%, auto 100%, auto auto;
+   */
+  // background-image: linear-gradient(var(--toolbar-bgcolor, transparent), var(--toolbar-bgcolor, transparent)),
+  //   linear-gradient(var(--toolbar-bgcolor), var(--toolbar-bgcolor)), var(--lwt-header-image, none) !important;
 
-.tab-background[multiselected="true"]:not([selected="true"]) > .tab-loading-burst:not([bursting]) {
-  background: color-mix(in srgb, currentColor 65%, transparent);
-  opacity: 0.3;
-}
-#TabsToolbar[brighttext]
-  .tab-background[multiselected="true"]:not([selected="true"])
-  > .tab-loading-burst:not([bursting]) {
-  opacity: 0.15;
+  background-attachment: scroll, fixed !important;
+  background-color: transparent !important;
+  background-image: linear-gradient(var(--uc-multiselected-tab-bgcolor), var(--uc-multiselected-tab-bgcolor)),
+                    var(--lwt-header-image, none) !important;
+  background-position: 0 0, right top !important;
+  background-repeat: repeat-x, no-repeat !important;
+  background-size: auto 100%, auto auto !important;
 }
 
-
 @include Option("userChrome.tab.connect_to_window") {
   .tab-background[multiselected=true] {
     outline: none !important;