diff --git a/clipboard-apis/async-navigator-clipboard-change-event.tentative.https.html b/clipboard-apis/async-navigator-clipboard-change-event.tentative.https.html
index 37e2e6a7bde3ef..bf32f4851b341c 100644
--- a/clipboard-apis/async-navigator-clipboard-change-event.tentative.https.html
+++ b/clipboard-apis/async-navigator-clipboard-change-event.tentative.https.html
@@ -25,48 +25,79 @@
       });
     }
 
+    let typesToSet_ = ["text/html", "web txt/csv"];
     button.onclick = () => document.execCommand("copy");
     document.oncopy = (ev) => {
       ev.preventDefault();
-      ev.clipboardData.setData("text/html", `<div>Test html</div>`);
+      for (let i = 0; i < typesToSet_.length; i++) {
+        const type = typesToSet_[i];
+        const data = new Blob([`Test data for ${type}`], {type: type});
+        ev.clipboardData.setData(type, data);
+      }
     };
 
-    function triggerCopyToClipboard() {
+    function triggerCopyToClipboard(typesToSet) {
+      if (typesToSet) {
+        typesToSet_ = typesToSet;
+      }
       return test_driver.click(button);
     }
 
     promise_test(async (test) => {
       let clipboardChangeEventCount = 0;
       let eventType = "";
+      let capturedEventTypes = null;
       navigator.clipboard.addEventListener("clipboardchange", (ev) => {
         clipboardChangeEventCount++;
         eventType = ev.type;
+        capturedEventTypes = ev.types;
       });
       await triggerCopyToClipboard();
       assert_equals(clipboardChangeEventCount, 1, "clipboardchange event should be called exactly once");
       assert_equals(eventType, "clipboardchange", "Event type should be 'clipboardchange'");
+      assert_true(capturedEventTypes.includes("text/html"), "types should contain 'text/html'");
+      assert_false(capturedEventTypes.includes("web txt/csv"), "types should not contain custom MIME type");
     }, "clipboardchange event is invoked");
 
     promise_test(async (test) => {
       await tryGrantWritePermission();
       let clipboardChangeEventCount = 0;
+      let capturedEventTypes = null;
       navigator.clipboard.addEventListener("clipboardchange", (ev) => {
         clipboardChangeEventCount++;
+        capturedEventTypes = ev.types;
       });
       await navigator.clipboard.writeText("Test text");
       await waitForRender();
       assert_equals(clipboardChangeEventCount, 1, "clipboardchange event should be called exactly once");
+      assert_true(capturedEventTypes.includes("text/plain"), "types should contain 'text/plain'");
     }, "clipboardchange event is invoked with async clipboard API");
 
     promise_test(async (test) => {
       let onClipboardChangeAttributeCount = 0;
-      navigator.clipboard.onclipboardchange = () => {
+      let capturedEventTypes = null;
+      navigator.clipboard.onclipboardchange = (ev) => {
         onClipboardChangeAttributeCount++;
+        capturedEventTypes = ev.types;
       };
       await triggerCopyToClipboard();
       assert_equals(onClipboardChangeAttributeCount, 1, "onclipboardchange attribute should be called exactly once");
+      assert_true(capturedEventTypes.includes("text/html"), "types should contain 'text/html'");
+      assert_false(capturedEventTypes.includes("web txt/csv"), "types should not contain custom MIME type");
     }, "clipboardchange event is invoked using onclipboardchange attribute");
 
+    promise_test(async (test) => {
+      let onClipboardChangeAttributeCount = 0;
+      let capturedEventTypes = null;
+      navigator.clipboard.onclipboardchange = (ev) => {
+        onClipboardChangeAttributeCount++;
+        capturedEventTypes = ev.types;
+      };
+      await triggerCopyToClipboard(["web txt/csv"]);
+      assert_equals(onClipboardChangeAttributeCount, 1, "onclipboardchange attribute should be called exactly once");
+      assert_equals(capturedEventTypes.length, 0, "clipboardchange event should have no types");
+    }, "clipboardchange event is invoked even when only custom MIME types are set");
+
     promise_test(async (test) => {
       let listenerCallCount = 0;
       function clipboardChangeListener() {
@@ -89,6 +120,55 @@
       assert_equals(listenerCallCount, 2, "Event listener should be called exactly once after re-adding");
     }, "clipboardchange event listener behavior when adding, removing, and re-adding");
 
+    promise_test(async (test) => {
+      // https://w3c.github.io/clipboard-apis/#mandatory-data-types-x
+      const standardTypes = [
+        "text/plain",
+        "text/html",
+        "image/png",
+      ];
+      const unsupportedTypes = [
+        "web application/custom",
+        "web web/proprietary",
+        "web x-custom/type",
+        "txt/json",
+        "text/rtf",
+        "image/svg+xml",
+        "text/uri-list",
+      ];
+      const allTypesToSet = [...standardTypes, ...unsupportedTypes];
+
+      let clipboardChangeEventCount = 0;
+      let capturedEventTypes = null;
+
+      navigator.clipboard.addEventListener("clipboardchange", (ev) => {
+        clipboardChangeEventCount++;
+        capturedEventTypes = ev.types;
+      });
+
+      await triggerCopyToClipboard(allTypesToSet);
+
+      assert_true(clipboardChangeEventCount == 1, "clipboardchange event should be invoked once");
+
+      // Check that types is a frozen array
+      assert_true(Array.isArray(capturedEventTypes), "types should be an array");
+      assert_true(Object.isFrozen(capturedEventTypes), "types should be frozen");
+
+      // Verify all standard types are included
+      for (const type of standardTypes) {
+        assert_true(capturedEventTypes.includes(type), `types should contain standard MIME type '${type}'`);
+      }
+
+      // Verify custom types are filtered out
+      for (const type of unsupportedTypes) {
+        assert_false(capturedEventTypes.includes(type), `types should not contain custom MIME type '${type}'`);
+      }
+
+      // Verify we have exactly the standard types and nothing else
+      assert_equals(capturedEventTypes.length, standardTypes.length,
+        "clipboardchange event types should contain exactly the standard MIME types");
+    }, "clipboardchange event exposes all standard MIME types and filters non-standard ones");
+
     promise_test(async (test) => {
       // Focus the document and acquire permission to write to the clipboard
       await test_driver.click(document.body);
@@ -97,6 +177,7 @@
       const iframe = document.getElementById('iframe');
 
       let frameEventCount = 0;
+      let capturedEventTypes = null;
       let focusEventFired = false;
       iframe.contentWindow.addEventListener("focus", () => {
         focusEventFired = true;
@@ -106,6 +187,7 @@
       iframe.contentWindow.navigator.clipboard.addEventListener("clipboardchange", () => {
         assert_true(focusEventFired, "focus event should fire before clipboardchange event");
         frameEventCount++;
+        capturedEventTypes = event.types;
       });
 
       // Ensure iFrame doesn't have the focus
@@ -114,7 +196,13 @@
 
       // Trigger multiple clipboard changes
       await navigator.clipboard.writeText("Test text");
-      await navigator.clipboard.writeText("Test text 2");
+
+      // Write HTML to clipboard to ensure the event captured only html and not txt
+      await navigator.clipboard.write([
+        new ClipboardItem({
+          "text/html": new Blob(["<p>Test HTML</p>"], {type: "text/html"})
+        })
+      ]);
       await waitForRender();
 
       assert_equals(frameEventCount, 0, "iframe should not recieve any clipboardchange event yet");
@@ -122,6 +210,9 @@
       iframe.focus();
       assert_true(iframe.contentWindow.document.hasFocus(), "iFrame should have focus");
       assert_equals(frameEventCount, 1, "iframe should receive event only 1 event after focus");
+      assert_equals(capturedEventTypes.length, 1, "clipboardchange event should only have one type");
+      assert_true(capturedEventTypes.includes("text/html"), "clipboardchange event should only have text/html type");
     }, "clipboardchange event should only fire in the focused context");
+
   </script>
 </body>
\ No newline at end of file