diff --git a/testing/web-platform/tests/css/css-view-transitions/3d-transform-incoming-ref.html b/testing/web-platform/tests/css/css-view-transitions/3d-transform-incoming-ref.html
index df5eaaca838239..a7d5e56db5bb2c 100644
--- a/testing/web-platform/tests/css/css-view-transitions/3d-transform-incoming-ref.html
+++ b/testing/web-platform/tests/css/css-view-transitions/3d-transform-incoming-ref.html
@@ -15,7 +15,6 @@
   background: blue;
 }
 .shared {
-  contain: layout;
   width: 100px;
   height: 100px;
 }
diff --git a/testing/web-platform/tests/css/css-view-transitions/3d-transform-incoming.html b/testing/web-platform/tests/css/css-view-transitions/3d-transform-incoming.html
index 0a0497122b185d..01debbcfcc1f0b 100644
--- a/testing/web-platform/tests/css/css-view-transitions/3d-transform-incoming.html
+++ b/testing/web-platform/tests/css/css-view-transitions/3d-transform-incoming.html
@@ -25,7 +25,6 @@
 }
 .shared {
   view-transition-name: shared;
-  contain: layout;
   width: 100px;
   height: 100px;
 }
@@ -34,7 +33,6 @@
   width: 10px;
   height: 10px;
   background: red;
-  contain: layout;
 }
 
 ::view-transition-group(hidden) { animation-duration: 300s; }
diff --git a/testing/web-platform/tests/css/css-view-transitions/3d-transform-outgoing-ref.html b/testing/web-platform/tests/css/css-view-transitions/3d-transform-outgoing-ref.html
index eede13140a57a0..393943e396a0d0 100644
--- a/testing/web-platform/tests/css/css-view-transitions/3d-transform-outgoing-ref.html
+++ b/testing/web-platform/tests/css/css-view-transitions/3d-transform-outgoing-ref.html
@@ -9,7 +9,6 @@
   background: green;
 }
 .shared {
-  contain: layout;
   width: 100px;
   height: 100px;
 }
diff --git a/testing/web-platform/tests/css/css-view-transitions/3d-transform-outgoing.html b/testing/web-platform/tests/css/css-view-transitions/3d-transform-outgoing.html
index 5cf83e4e672de4..1cf74c8f08af8b 100644
--- a/testing/web-platform/tests/css/css-view-transitions/3d-transform-outgoing.html
+++ b/testing/web-platform/tests/css/css-view-transitions/3d-transform-outgoing.html
@@ -26,7 +26,6 @@
 }
 .shared {
   view-transition-name: shared;
-  contain: layout;
   width: 100px;
   height: 100px;
 }
@@ -35,7 +34,6 @@
   width: 10px;
   height: 10px;
   background: red;
-  contain: layout;
 }
 
 ::view-transition-group(hidden) { animation-duration: 300s; }
diff --git a/testing/web-platform/tests/css/css-view-transitions/css-tags-paint-order-ref.html b/testing/web-platform/tests/css/css-view-transitions/css-tags-paint-order-ref.html
index 53f6b380c6300b..780d5fbd453e9f 100644
--- a/testing/web-platform/tests/css/css-view-transitions/css-tags-paint-order-ref.html
+++ b/testing/web-platform/tests/css/css-view-transitions/css-tags-paint-order-ref.html
@@ -5,7 +5,6 @@
 
 <style>
 div {
-  contain: layout;
   position: absolute;
   top: 50px;
   width: 100px;
diff --git a/testing/web-platform/tests/css/css-view-transitions/css-tags-paint-order.html b/testing/web-platform/tests/css/css-view-transitions/css-tags-paint-order.html
index ee1d260e1e8d81..c0e8769b473052 100644
--- a/testing/web-platform/tests/css/css-view-transitions/css-tags-paint-order.html
+++ b/testing/web-platform/tests/css/css-view-transitions/css-tags-paint-order.html
@@ -7,7 +7,6 @@
 
 <script src="/common/reftest-wait.js"></script>
 <style>
-div { contain: layout; }
 #one {
   background: green;
   width: 100px;
diff --git a/testing/web-platform/tests/css/css-view-transitions/dialog-in-top-layer-during-transition-new.html b/testing/web-platform/tests/css/css-view-transitions/dialog-in-top-layer-during-transition-new.html
index e84167a24892cb..5f93672fc14f03 100644
--- a/testing/web-platform/tests/css/css-view-transitions/dialog-in-top-layer-during-transition-new.html
+++ b/testing/web-platform/tests/css/css-view-transitions/dialog-in-top-layer-during-transition-new.html
@@ -17,7 +17,6 @@
   padding: 0;
 
   view-transition-name: dialog;
-  contain: layout;
 }
 
 #target::backdrop {
@@ -26,7 +25,6 @@
   background: grey;
 
   view-transition-name: backdrop;
-  contain: layout;
 }
 
 .hidden {
diff --git a/testing/web-platform/tests/css/css-view-transitions/dialog-in-top-layer-during-transition-old.html b/testing/web-platform/tests/css/css-view-transitions/dialog-in-top-layer-during-transition-old.html
index 672295cd3bd725..9130ea18509506 100644
--- a/testing/web-platform/tests/css/css-view-transitions/dialog-in-top-layer-during-transition-old.html
+++ b/testing/web-platform/tests/css/css-view-transitions/dialog-in-top-layer-during-transition-old.html
@@ -17,7 +17,6 @@
   padding: 0;
 
   view-transition-name: dialog;
-  contain: layout;
 }
 
 #target::backdrop {
@@ -26,7 +25,6 @@
   background: grey;
 
   view-transition-name: backdrop;
-  contain: layout;
 }
 
 .hidden {
diff --git a/testing/web-platform/tests/css/css-view-transitions/element-with-overflow.html b/testing/web-platform/tests/css/css-view-transitions/element-with-overflow.html
index b600bcec27e6a5..678e0a062e0745 100644
--- a/testing/web-platform/tests/css/css-view-transitions/element-with-overflow.html
+++ b/testing/web-platform/tests/css/css-view-transitions/element-with-overflow.html
@@ -12,14 +12,12 @@
     height: 10px;
     view-transition-name: hidden;
     background: green;
-    contain: layout;
   }
 
   .target {
     width: 100px;
     height: 100px;
     background: lightblue;
-    contain: layout;
     view-transition-name: target;
   }
   .inner {
diff --git a/testing/web-platform/tests/css/css-view-transitions/new-content-element-writing-modes.html b/testing/web-platform/tests/css/css-view-transitions/new-content-element-writing-modes.html
index 84b6fcf517e2c8..d7740d78f54f52 100644
--- a/testing/web-platform/tests/css/css-view-transitions/new-content-element-writing-modes.html
+++ b/testing/web-platform/tests/css/css-view-transitions/new-content-element-writing-modes.html
@@ -27,9 +27,6 @@
   contain: paint;
   border: 1px solid black;
 }
-.source {
-  contain: layout;
-}
 #target {
   background: red;
   position: absolute;
diff --git a/testing/web-platform/tests/css/css-view-transitions/new-content-object-fit-fill.html b/testing/web-platform/tests/css/css-view-transitions/new-content-object-fit-fill.html
index 286528305b8c22..b891eee16d5e93 100644
--- a/testing/web-platform/tests/css/css-view-transitions/new-content-object-fit-fill.html
+++ b/testing/web-platform/tests/css/css-view-transitions/new-content-object-fit-fill.html
@@ -29,7 +29,6 @@
   width: 10px;
   height: 10px;
   view-transition-name: hidden;
-  contain: layout;
 }
 
 html::view-transition-group(target) {
diff --git a/testing/web-platform/tests/css/css-view-transitions/new-content-object-fit-none.html b/testing/web-platform/tests/css/css-view-transitions/new-content-object-fit-none.html
index cad836678e94ba..d4b81b1a0eeadb 100644
--- a/testing/web-platform/tests/css/css-view-transitions/new-content-object-fit-none.html
+++ b/testing/web-platform/tests/css/css-view-transitions/new-content-object-fit-none.html
@@ -21,7 +21,6 @@
   width: 10px;
   height: 10px;
   view-transition-name: hidden;
-  contain: layout;
 }
 
 html::view-transition-group(target) {
diff --git a/testing/web-platform/tests/css/css-view-transitions/no-containment-on-new-element-mid-transition.html b/testing/web-platform/tests/css/css-view-transitions/no-containment-on-new-element-mid-transition.html
deleted file mode 100644
index dc5ede4d8d34dd..00000000000000
--- a/testing/web-platform/tests/css/css-view-transitions/no-containment-on-new-element-mid-transition.html
+++ /dev/null
@@ -1,38 +0,0 @@
-<!DOCTYPE html>
-<html>
-<title>View transitions: transition skipped if no containment on new element after animation started</title>
-<link rel="help" href="https://www.w3.org/TR/css-view-transitions-1/">
-<link rel="author" href="mailto:khushalsagar@chromium.org">
-
-<script src="/resources/testharness.js"></script>
-<script src="/resources/testharnessreport.js"></script>
-
-<style>
-div {
-  width: 100px;
-  height: 100px;
-  background: blue;
-  view-transition-name: target;
-  contain: paint;
-}
-
-html::view-transition-group(target) {
-  animation-duration: 300s;
-}
-</style>
-
-<div id=first></div>
-
-<script>
-promise_test(async t => {
-  assert_implements(document.startViewTransition, "Missing document.startViewTransition");
-  return new Promise(async (resolve, reject) => {
-    let transition = document.startViewTransition();
-    await transition.updateCallbackDone;
-    await transition.ready;
-
-    transition.finished.then(resolve, reject);
-    first.style.contain = "none";
-  });
-}, "new element becoming uncontained should skip the transition");
-</script>
diff --git a/testing/web-platform/tests/css/css-view-transitions/no-containment-on-new-element.html b/testing/web-platform/tests/css/css-view-transitions/no-containment-on-new-element.html
deleted file mode 100644
index 57f148309b4a93..00000000000000
--- a/testing/web-platform/tests/css/css-view-transitions/no-containment-on-new-element.html
+++ /dev/null
@@ -1,47 +0,0 @@
-<!DOCTYPE html>
-<html>
-<title>View transitions: transition skipped if no containment on new element</title>
-<link rel="help" href="https://www.w3.org/TR/css-view-transitions-1/">
-<link rel="author" href="mailto:khushalsagar@chromium.org">
-
-<script src="/resources/testharness.js"></script>
-<script src="/resources/testharnessreport.js"></script>
-
-<style>
-div {
-  width: 100px;
-  height: 100px;
-  background: blue;
-  view-transition-name: target;
-  contain: paint;
-}
-</style>
-
-<div id=first></div>
-
-<script>
-promise_test(async t => {
-  assert_implements(document.startViewTransition, "Missing document.startViewTransition");
-  return new Promise(async (resolve, reject) => {
-    let transition = document.startViewTransition(() => {
-      first.style.contain = "none";
-    });
-
-    let readyRejected = false;
-    transition.ready.then(reject, () => { readyRejected = true; });
-
-    let updateCallbackDone = false;
-    transition.updateCallbackDone.then(() => { updateCallbackDone = true; }, reject);
-    transition.finished.then(() => {
-      assert_true(readyRejected, "ready not rejected");
-      assert_true(updateCallbackDone, "dom not updated");
-
-      if (window.getComputedStyle(first).contain == "none")
-        resolve();
-      else
-        reject("dom update callback did not run");
-
-    }, reject);
-  });
-}, "uncontained new element should skip the transition");
-</script>
diff --git a/testing/web-platform/tests/css/css-view-transitions/no-containment-on-old-element.html b/testing/web-platform/tests/css/css-view-transitions/no-containment-on-old-element.html
deleted file mode 100644
index b0af95bf6ceb56..00000000000000
--- a/testing/web-platform/tests/css/css-view-transitions/no-containment-on-old-element.html
+++ /dev/null
@@ -1,46 +0,0 @@
-<!DOCTYPE html>
-<html>
-<title>View transitions: transition skipped if no containment on old element</title>
-<link rel="help" href="https://www.w3.org/TR/css-view-transitions-1/">
-<link rel="author" href="mailto:khushalsagar@chromium.org">
-
-<script src="/resources/testharness.js"></script>
-<script src="/resources/testharnessreport.js"></script>
-
-<style>
-div {
-  width: 100px;
-  height: 100px;
-  background: blue;
-  view-transition-name: target;
-}
-</style>
-
-<div id=first></div>
-
-<script>
-promise_test(async t => {
-  assert_implements(document.startViewTransition, "Missing document.startViewTransition");
-  return new Promise(async (resolve, reject) => {
-    let transition = document.startViewTransition(() => {
-      first.style.contain = "paint";
-    });
-
-    let readyRejected = false;
-    transition.ready.then(reject, () => { readyRejected = true; });
-
-    let updateCallbackDone = false;
-    transition.updateCallbackDone.then(() => { updateCallbackDone = true; }, reject);
-    transition.finished.then(() => {
-      assert_true(readyRejected, "ready not rejected");
-      assert_true(updateCallbackDone, "dom not updated");
-
-      if (window.getComputedStyle(first).contain == "paint")
-        resolve();
-      else
-        reject("dom update callback did not run");
-
-    }, reject);
-  });
-}, "uncontained old element should skip the transition");
-</script>
diff --git a/testing/web-platform/tests/css/css-view-transitions/old-content-object-fit-fill.html b/testing/web-platform/tests/css/css-view-transitions/old-content-object-fit-fill.html
index 9a660266baade6..9ad8b14843fbb0 100644
--- a/testing/web-platform/tests/css/css-view-transitions/old-content-object-fit-fill.html
+++ b/testing/web-platform/tests/css/css-view-transitions/old-content-object-fit-fill.html
@@ -29,7 +29,6 @@
   width: 10px;
   height: 10px;
   view-transition-name: hidden;
-  contain: layout;
 }
 
 html::view-transition-group(target) {
diff --git a/testing/web-platform/tests/css/css-view-transitions/old-content-object-fit-none.html b/testing/web-platform/tests/css/css-view-transitions/old-content-object-fit-none.html
index 115fd0611498d4..1275aece7cae48 100644
--- a/testing/web-platform/tests/css/css-view-transitions/old-content-object-fit-none.html
+++ b/testing/web-platform/tests/css/css-view-transitions/old-content-object-fit-none.html
@@ -21,7 +21,6 @@
   width: 10px;
   height: 10px;
   view-transition-name: hidden;
-  contain: layout;
 }
 
 html::view-transition-group(target) {
diff --git a/testing/web-platform/tests/css/css-view-transitions/only-child-group.html b/testing/web-platform/tests/css/css-view-transitions/only-child-group.html
index 034df41dde165f..b4089114560db7 100644
--- a/testing/web-platform/tests/css/css-view-transitions/only-child-group.html
+++ b/testing/web-platform/tests/css/css-view-transitions/only-child-group.html
@@ -28,9 +28,6 @@
   color: red;
 }
 
-div {
-  contain: layout;
-}
 </style>
 <div id="target"></div>
 <div id="target2"></div>
diff --git a/testing/web-platform/tests/css/css-view-transitions/only-child-new.html b/testing/web-platform/tests/css/css-view-transitions/only-child-new.html
index 2f8a7a4023ec7f..085793b73b5f5c 100644
--- a/testing/web-platform/tests/css/css-view-transitions/only-child-new.html
+++ b/testing/web-platform/tests/css/css-view-transitions/only-child-new.html
@@ -28,10 +28,6 @@
   color: red;
 }
 
-#target {
-  contain: layout;
-}
-
 </style>
 <div id="target"></div>
 
diff --git a/testing/web-platform/tests/css/css-view-transitions/only-child-old.html b/testing/web-platform/tests/css/css-view-transitions/only-child-old.html
index 4ca6fed20ce7b2..b6a7367886d9d9 100644
--- a/testing/web-platform/tests/css/css-view-transitions/only-child-old.html
+++ b/testing/web-platform/tests/css/css-view-transitions/only-child-old.html
@@ -28,10 +28,6 @@
   color: red;
 }
 
-#target {
-  contain: layout;
-}
-
 </style>
 <div id="target"></div>
 
diff --git a/testing/web-platform/tests/css/css-view-transitions/paused-animation-at-end.html b/testing/web-platform/tests/css/css-view-transitions/paused-animation-at-end.html
index 47db0a6fcd6745..ae9176ea26c242 100644
--- a/testing/web-platform/tests/css/css-view-transitions/paused-animation-at-end.html
+++ b/testing/web-platform/tests/css/css-view-transitions/paused-animation-at-end.html
@@ -11,7 +11,6 @@
 #target {
   width: 100px;
   height: 100px;
-  contain: layout;
   view-transition-name: target;
 }
 .one {
diff --git a/testing/web-platform/tests/css/css-view-transitions/scroller-child-abspos-ref.html b/testing/web-platform/tests/css/css-view-transitions/scroller-child-abspos-ref.html
index fd84030f71b773..ed118e633f013e 100644
--- a/testing/web-platform/tests/css/css-view-transitions/scroller-child-abspos-ref.html
+++ b/testing/web-platform/tests/css/css-view-transitions/scroller-child-abspos-ref.html
@@ -5,7 +5,6 @@
 
 <style>
 #target {
-  contain: layout;
   width: 200px;
   height: 200px;
   background: yellow;
diff --git a/testing/web-platform/tests/css/css-view-transitions/scroller-child-abspos.html b/testing/web-platform/tests/css/css-view-transitions/scroller-child-abspos.html
index 952a2679aabdbb..6c5b16dc01ddb7 100644
--- a/testing/web-platform/tests/css/css-view-transitions/scroller-child-abspos.html
+++ b/testing/web-platform/tests/css/css-view-transitions/scroller-child-abspos.html
@@ -9,7 +9,6 @@
 
 <style>
 #target {
-  contain: layout;
   view-transition-name: target;
   width: 200px;
   height: 200px;
diff --git a/testing/web-platform/tests/css/css-view-transitions/scroller-child-ref.html b/testing/web-platform/tests/css/css-view-transitions/scroller-child-ref.html
index be7e69ac312be3..4ff2b2c5ae355f 100644
--- a/testing/web-platform/tests/css/css-view-transitions/scroller-child-ref.html
+++ b/testing/web-platform/tests/css/css-view-transitions/scroller-child-ref.html
@@ -5,7 +5,6 @@
 
 <style>
 #target {
-  contain: layout;
   width: 500px;
   height: 500px;
   background: yellow;
diff --git a/testing/web-platform/tests/css/css-view-transitions/scroller-child.html b/testing/web-platform/tests/css/css-view-transitions/scroller-child.html
index 2c8a0c4477004a..72b405d64c0446 100644
--- a/testing/web-platform/tests/css/css-view-transitions/scroller-child.html
+++ b/testing/web-platform/tests/css/css-view-transitions/scroller-child.html
@@ -9,7 +9,6 @@
 
 <style>
 #target {
-  contain: layout;
   view-transition-name: target;
   width: 500px;
   height: 500px;
diff --git a/testing/web-platform/tests/css/css-view-transitions/scroller-ref.html b/testing/web-platform/tests/css/css-view-transitions/scroller-ref.html
index 9a764e74c7cb73..27a2329ee04341 100644
--- a/testing/web-platform/tests/css/css-view-transitions/scroller-ref.html
+++ b/testing/web-platform/tests/css/css-view-transitions/scroller-ref.html
@@ -9,7 +9,6 @@
   width: 100px;
   height: 100px;
   background: blue;
-  contain: layout;
 }
 
 #child {
diff --git a/testing/web-platform/tests/css/css-view-transitions/scroller.html b/testing/web-platform/tests/css/css-view-transitions/scroller.html
index ecc413b2550747..c86fce2353a448 100644
--- a/testing/web-platform/tests/css/css-view-transitions/scroller.html
+++ b/testing/web-platform/tests/css/css-view-transitions/scroller.html
@@ -13,7 +13,6 @@
   width: 100px;
   height: 100px;
   background: blue;
-  contain: layout;
   view-transition-name: target;
 }
 
diff --git a/testing/web-platform/tests/css/css-view-transitions/set-current-time-ref.html b/testing/web-platform/tests/css/css-view-transitions/set-current-time-ref.html
index 2cf8742768aa35..9cf41ec1166ed8 100644
--- a/testing/web-platform/tests/css/css-view-transitions/set-current-time-ref.html
+++ b/testing/web-platform/tests/css/css-view-transitions/set-current-time-ref.html
@@ -6,7 +6,6 @@
 .target {
   width: 100px;
   height: 100px;
-  contain: layout;
   background: blue;
   opacity: 0.5;
 }
diff --git a/testing/web-platform/tests/css/css-view-transitions/set-current-time-transform-ref.html b/testing/web-platform/tests/css/css-view-transitions/set-current-time-transform-ref.html
index 2e977ce262776c..556d3f544edcd6 100644
--- a/testing/web-platform/tests/css/css-view-transitions/set-current-time-transform-ref.html
+++ b/testing/web-platform/tests/css/css-view-transitions/set-current-time-transform-ref.html
@@ -13,7 +13,6 @@
 #target {
   width: 100px;
   height: 100px;
-  contain: layout;
   background: blue;
   view-transition-name: target;
   position: relative;
diff --git a/testing/web-platform/tests/css/css-view-transitions/set-current-time-transform.html b/testing/web-platform/tests/css/css-view-transitions/set-current-time-transform.html
index 9958a0bdca05a4..41e3d3f89dae0e 100644
--- a/testing/web-platform/tests/css/css-view-transitions/set-current-time-transform.html
+++ b/testing/web-platform/tests/css/css-view-transitions/set-current-time-transform.html
@@ -10,7 +10,6 @@
 #target {
   width: 100px;
   height: 100px;
-  contain: layout;
   background: blue;
   view-transition-name: target;
   position: relative;
diff --git a/testing/web-platform/tests/css/css-view-transitions/set-current-time.html b/testing/web-platform/tests/css/css-view-transitions/set-current-time.html
index 4047623a9af086..2e37626a9e07be 100644
--- a/testing/web-platform/tests/css/css-view-transitions/set-current-time.html
+++ b/testing/web-platform/tests/css/css-view-transitions/set-current-time.html
@@ -11,7 +11,6 @@
 .target {
   width: 100px;
   height: 100px;
-  contain: layout;
   background: blue;
   view-transition-name: target;
 }
diff --git a/testing/web-platform/tests/css/css-view-transitions/view-transition-name-on-added-element.html b/testing/web-platform/tests/css/css-view-transitions/view-transition-name-on-added-element.html
deleted file mode 100644
index 643121e8185432..00000000000000
--- a/testing/web-platform/tests/css/css-view-transitions/view-transition-name-on-added-element.html
+++ /dev/null
@@ -1,37 +0,0 @@
-<!DOCTYPE html>
-<html>
-<title>View transitions: ensures view-transition-name is tracked on element added by script</title>
-<link rel="help" href="https://www.w3.org/TR/css-view-transitions-1/">
-<link rel="author" href="mailto:khushalsagar@chromium.org">
-
-<script src="/resources/testharness.js"></script>
-<script src="/resources/testharnessreport.js"></script>
-
-<style>
-#first {
-  width: 100px;
-  height: 100px;
-  background: blue;
-  view-transition-name: first;
-}
-</style>
-<body>
-  <div>
-    <div id=first></div>
-  </div>
-</body>
-<script>
-promise_test(async t => {
-  assert_implements(document.startViewTransition, "Missing document.startViewTransition");
-  return new Promise((resolve, reject) => {
-    // Remove and add an uncontained element. Even though this element doesn't
-    // create a stacking context its verified during the transition.
-    const element = document.getElementById("first");
-    element.remove();
-    document.body.appendChild(element);
-
-    let transition = document.startViewTransition();
-    transition.ready.then(reject, resolve);
-  });
-}, "view-transition-name on an element added by script should be visited when discovering named elements");
-</script>