diff --git a/testing/web-platform/tests/html/browsers/the-window-object/support/window-open-popup-target.html b/testing/web-platform/tests/html/browsers/the-window-object/support/window-open-popup-target.html
new file mode 100644
index 0000000000000..a0588de82970a
--- /dev/null
+++ b/testing/web-platform/tests/html/browsers/the-window-object/support/window-open-popup-target.html
@@ -0,0 +1,24 @@
+<!DOCTYPE html>
+<script>
+  var channelName = window.name;
+  var channel = new BroadcastChannel(channelName);
+  const allBarProps = [
+    window.locationbar.visible,
+    window.menubar.visible,
+    window.personalbar.visible,
+    window.scrollbars.visible,
+    window.statusbar.visible,
+    window.toolbar.visible
+  ];
+  const allTrue = allBarProps.every(x=>x);
+  const allFalse = allBarProps.every(x=>!x);
+  channel.postMessage({isPopup: allFalse, mixedState: !allTrue && !allFalse});
+
+  // Because messages are not delivered synchronously and because closing a
+  // browsing context prompts the eventual clearing of all task sources, this
+  // document should not be closed until the opener document has confirmed
+  // receipt.
+  channel.onmessage = function() {
+    window.close();
+  };
+</script>
\ No newline at end of file
diff --git a/testing/web-platform/tests/html/browsers/the-window-object/window-open-popup-behavior.html b/testing/web-platform/tests/html/browsers/the-window-object/window-open-popup-behavior.html
new file mode 100644
index 0000000000000..258698d94d9ad
--- /dev/null
+++ b/testing/web-platform/tests/html/browsers/the-window-object/window-open-popup-behavior.html
@@ -0,0 +1,51 @@
+<!DOCTYPE html>
+<meta charset=utf-8>
+<meta name="timeout" content="long">
+<title>Window.open popup behavior</title>
+<link rel="author" href="masonf@chromium.org">
+<link rel="help" href="https://html.spec.whatwg.org/multipage/window-object.html#window-open-steps">
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+
+<script>
+function testOne(windowFeatures, expectPopup) {
+  const windowName = Math.round(Math.random()*1e12);
+  const channel = new BroadcastChannel(windowName);
+  var w;
+  promise_test(() => {
+    return new Promise(resolve => {
+      w = window.open("support/window-open-popup-target.html", windowName, windowFeatures);
+      channel.addEventListener('message', resolve);
+    }).then(e => {
+      // Send message first so if asserts throw the popup is still closed
+      channel.postMessage(null);
+      assert_false(e.data.mixedState, "No mixed state");
+      assert_equals(e.data.isPopup, expectPopup, "Popup state");
+    });
+  },`${windowFeatures} (expect ${expectPopup ? "popup" : "tab"})`);
+}
+
+// No windowpreferences at all - tab.
+testOne(undefined, /*expectPopup=*/false);
+
+// Test all permutations of these properties:
+const features = ["location","toolbar","menubar","resizable","scrollbars","status"];
+const nProps = features.length;
+const skip = 7; // To speed up the test, don't test all values. Skip 7 to pseudo-randomize.
+for(let i=0;i<2**nProps;i+=skip) {
+  const enableVec = Number(i).toString(2).padStart(nProps,'0').split('').map(s => (s==="1"));
+  let windowFeatures = [];
+  for(let i=0;i<nProps;++i) {
+    if (enableVec[i])
+      windowFeatures.push(features[i] + "=yes");
+  }
+  windowFeatures = windowFeatures.join(',');
+  // We get a popup we got windowFeatures, and any of them are false:
+  const expectPopup = !!windowFeatures.length && (!(enableVec[0] || enableVec[1]) || !enableVec[2] || !enableVec[3] || !enableVec[4] || !enableVec[5]);
+  testOne(windowFeatures, expectPopup);
+  testOne(windowFeatures + ",noopener", /*expectPopup=*/false);
+  testOne(windowFeatures + ",noreferrer", /*expectPopup=*/false);
+  testOne(windowFeatures + ",popup", /*expectPopup=*/true); // "popup" feature = popup
+  testOne(windowFeatures + ",noopener,noreferrer,popup", /*expectPopup=*/false);
+}
+</script>
