diff --git a/packages/block-editor/src/components/block-canvas/style.scss b/packages/block-editor/src/components/block-canvas/style.scss
index 4317672319544..9e924cb79bace 100644
--- a/packages/block-editor/src/components/block-canvas/style.scss
+++ b/packages/block-editor/src/components/block-canvas/style.scss
@@ -1,7 +1,7 @@
 iframe[name="editor-canvas"] {
+	box-sizing: border-box;
 	width: 100%;
 	height: 100%;
 	display: block;
-	background-color: $gray-300;
-	box-sizing: border-box;
+	background-color: transparent;
 }
diff --git a/packages/edit-site/src/components/layout/style.scss b/packages/edit-site/src/components/layout/style.scss
index 8c15cdae33881..0c5412b6d765b 100644
--- a/packages/edit-site/src/components/layout/style.scss
+++ b/packages/edit-site/src/components/layout/style.scss
@@ -4,6 +4,11 @@
 	color: $gray-400;
 	display: flex;
 	flex-direction: column;
+
+	// Show a dark background in "frame" mode to avoid edge artifacts.
+	&:not(.is-full-canvas) .editor-visual-editor {
+		background: $gray-900;
+	}
 }
 
 .edit-site-layout__hub {