diff --git a/html/browsers/the-window-object/apis-for-creating-and-navigating-browsing-contexts-by-name/open-features-tokenization-height-vs-innerheight.html b/html/browsers/the-window-object/apis-for-creating-and-navigating-browsing-contexts-by-name/open-features-tokenization-height-vs-innerheight.html
new file mode 100644
index 00000000000000..8fd4804785b7eb
--- /dev/null
+++ b/html/browsers/the-window-object/apis-for-creating-and-navigating-browsing-contexts-by-name/open-features-tokenization-height-vs-innerheight.html
@@ -0,0 +1,70 @@
+<!DOCTYPE html>
+<meta charset="utf-8">
+<title>HTML: window.open `features`: tokenization -- size features `height` vs `innerheight`</title>
+<meta name=timeout content=long>
+<link rel="help" href="https://html.spec.whatwg.org/multipage/#apis-for-creating-and-navigating-browsing-contexts-by-name">
+
+<!-- user agents are not required to support open features other than `noopener`
+     and on some platforms position and size features don't make sense -->
+<meta name="flags" content="may" />
+
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="/common/PrefixedPostMessage.js"></script>
+<script>
+var windowURL = 'resources/message-opener.html';
+var featuresPrefix = `top=0,left=0,width=401,`;
+
+setup (() => {
+  // Before running tests, open a window using features that mimic
+  // what would happen if the feature tested here were set to 0
+  // for comparison later.
+  var featureString = `${featuresPrefix}height=0`;
+  var prefixedMessage = new PrefixedMessageTest();
+  prefixedMessage.onMessage((data, e) => {
+    e.source.close();
+    runWindowTests(data);
+  });
+  var win = window.open(prefixedMessage.url(windowURL), '', featureString);
+});
+
+function runWindowTests (baselineDimensions) {
+
+  // The last specified feature is used
+  [ 'height=401,height=402',
+    'height=401,innerheight=402',
+    'innerheight=401,height=402',
+    'innerheight=401,innerheight=402',
+  ].forEach((features, idx, arr) => {
+    async_test(t => {
+      var prefixedMessage = new PrefixedMessageTest();
+      prefixedMessage.onMessage(t.step_func_done((data, e) => {
+        e.source.close();
+        assert_equals(data.height, 402);
+      }));
+      var win = window.open(prefixedMessage.url(windowURL), '', featuresPrefix + features);
+    }, `${format_value(features)} repeated height/innerheight features`);
+  });
+
+  // The last specified feature is used even if the value is 0 or error
+  [ 'height=401,height=0',
+    'height=401,innerheight=0',
+    'innerheight=401,height=0',
+    'innerheight=401,innerheight=0',
+    'height=401,height=error',
+    'height=401,innerheight=error',
+    'innerheight=401,height=error',
+    'innerheight=401,innerheight=error',
+  ].forEach((features, idx, arr) => {
+    async_test(t => {
+      var prefixedMessage = new PrefixedMessageTest();
+      prefixedMessage.onMessage(t.step_func_done((data, e) => {
+        e.source.close();
+        assert_equals(data.height, baselineDimensions.height);
+      }));
+      var win = window.open(prefixedMessage.url(windowURL), '', featuresPrefix + features);
+    }, `${format_value(features)} repeated height/innerheight features where the last one is 0 or error`);
+  });
+}
+
+</script>
diff --git a/html/browsers/the-window-object/apis-for-creating-and-navigating-browsing-contexts-by-name/open-features-tokenization-left-vs-screenx.html b/html/browsers/the-window-object/apis-for-creating-and-navigating-browsing-contexts-by-name/open-features-tokenization-left-vs-screenx.html
new file mode 100644
index 00000000000000..908bb55b559c81
--- /dev/null
+++ b/html/browsers/the-window-object/apis-for-creating-and-navigating-browsing-contexts-by-name/open-features-tokenization-left-vs-screenx.html
@@ -0,0 +1,70 @@
+<!DOCTYPE html>
+<meta charset="utf-8">
+<title>HTML: window.open `features`: tokenization -- position features `left` vs `screenx`</title>
+<meta name=timeout content=long>
+<link rel="help" href="https://html.spec.whatwg.org/multipage/#apis-for-creating-and-navigating-browsing-contexts-by-name">
+
+<!-- user agents are not required to support open features other than `noopener`
+     and on some platforms position and size features don't make sense -->
+<meta name="flags" content="may" />
+
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="/common/PrefixedPostMessage.js"></script>
+<script>
+var windowURL = 'resources/message-opener.html';
+var featuresPrefix = `width=401,height=204,top=0,`;
+
+setup (() => {
+  // Before running tests, open a window using features that mimic
+  // what would happen if the feature tested here were set to 0
+  // for comparison later.
+  var featureString = `${featuresPrefix}left=0`;
+  var prefixedMessage = new PrefixedMessageTest();
+  prefixedMessage.onMessage((data, e) => {
+    e.source.close();
+    runWindowTests(data);
+  });
+  var win = window.open(prefixedMessage.url(windowURL), '', featureString);
+});
+
+function runWindowTests (baselineDimensions) {
+
+  // The last specified feature is used
+  [ 'left=101,left=102',
+    'left=101,screenx=102',
+    'screenx=101,left=102',
+    'screenx=101,screenx=102',
+  ].forEach((features, idx, arr) => {
+    async_test(t => {
+      var prefixedMessage = new PrefixedMessageTest();
+      prefixedMessage.onMessage(t.step_func_done((data, e) => {
+        e.source.close();
+        assert_equals(data.left, 102);
+      }));
+      var win = window.open(prefixedMessage.url(windowURL), '', featuresPrefix + features);
+    }, `${format_value(features)} repeated left/screenx features`);
+  });
+
+  // The last specified feature is used even if the value is 0 or error
+  [ 'left=101,left=0',
+    'left=101,screenx=0',
+    'screenx=101,left=0',
+    'screenx=101,screenx=0',
+    'left=101,left=error',
+    'left=101,screenx=error',
+    'screenx=101,left=error',
+    'screenx=101,screenx=error',
+  ].forEach((features, idx, arr) => {
+    async_test(t => {
+      var prefixedMessage = new PrefixedMessageTest();
+      prefixedMessage.onMessage(t.step_func_done((data, e) => {
+        e.source.close();
+        assert_equals(data.left, baselineDimensions.left);
+      }));
+      var win = window.open(prefixedMessage.url(windowURL), '', featuresPrefix + features);
+    }, `${format_value(features)} repeated left/screenx features where the last one is 0 or error`);
+  });
+}
+
+</script>
diff --git a/html/browsers/the-window-object/apis-for-creating-and-navigating-browsing-contexts-by-name/open-features-tokenization-top-vs-screeny.html b/html/browsers/the-window-object/apis-for-creating-and-navigating-browsing-contexts-by-name/open-features-tokenization-top-vs-screeny.html
new file mode 100644
index 00000000000000..a04f7c384a0774
--- /dev/null
+++ b/html/browsers/the-window-object/apis-for-creating-and-navigating-browsing-contexts-by-name/open-features-tokenization-top-vs-screeny.html
@@ -0,0 +1,70 @@
+<!DOCTYPE html>
+<meta charset="utf-8">
+<title>HTML: window.open `features`: tokenization -- position features `top` vs `screeny`</title>
+<meta name=timeout content=long>
+<link rel="help" href="https://html.spec.whatwg.org/multipage/#apis-for-creating-and-navigating-browsing-contexts-by-name">
+
+<!-- user agents are not required to support open features other than `noopener`
+     and on some platforms position and size features don't make sense -->
+<meta name="flags" content="may" />
+
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="/common/PrefixedPostMessage.js"></script>
+<script>
+var windowURL = 'resources/message-opener.html';
+var featuresPrefix = `width=401,height=204,left=0,`;
+
+setup (() => {
+  // Before running tests, open a window using features that mimic
+  // what would happen if the feature tested here were set to 0
+  // for comparison later.
+  var featureString = `${featuresPrefix}top=0`;
+  var prefixedMessage = new PrefixedMessageTest();
+  prefixedMessage.onMessage((data, e) => {
+    e.source.close();
+    runWindowTests(data);
+  });
+  var win = window.open(prefixedMessage.url(windowURL), '', featureString);
+});
+
+function runWindowTests (baselineDimensions) {
+
+  // The last specified feature is used
+  [ 'top=101,top=102',
+    'top=101,screeny=102',
+    'screeny=101,top=102',
+    'screeny=101,screeny=102',
+  ].forEach((features, idx, arr) => {
+    async_test(t => {
+      var prefixedMessage = new PrefixedMessageTest();
+      prefixedMessage.onMessage(t.step_func_done((data, e) => {
+        e.source.close();
+        assert_equals(data.top, 102);
+      }));
+      var win = window.open(prefixedMessage.url(windowURL), '', featuresPrefix + features);
+    }, `${format_value(features)} repeated top/screeny features`);
+  });
+
+  // The last specified feature is used even if the value is 0 or error
+  [ 'top=101,top=0',
+    'top=101,screeny=0',
+    'screeny=101,top=0',
+    'screeny=101,screeny=0',
+    'top=101,top=error',
+    'top=101,screeny=error',
+    'screeny=101,top=error',
+    'screeny=101,screeny=error',
+  ].forEach((features, idx, arr) => {
+    async_test(t => {
+      var prefixedMessage = new PrefixedMessageTest();
+      prefixedMessage.onMessage(t.step_func_done((data, e) => {
+        e.source.close();
+        assert_equals(data.top, baselineDimensions.top);
+      }));
+      var win = window.open(prefixedMessage.url(windowURL), '', featuresPrefix + features);
+    }, `${format_value(features)} repeated top/screeny features where the last one is 0 or error`);
+  });
+}
+
+</script>
diff --git a/html/browsers/the-window-object/apis-for-creating-and-navigating-browsing-contexts-by-name/open-features-tokenization-width-vs-innerwidth.html b/html/browsers/the-window-object/apis-for-creating-and-navigating-browsing-contexts-by-name/open-features-tokenization-width-vs-innerwidth.html
new file mode 100644
index 00000000000000..b9b05ef5a694b5
--- /dev/null
+++ b/html/browsers/the-window-object/apis-for-creating-and-navigating-browsing-contexts-by-name/open-features-tokenization-width-vs-innerwidth.html
@@ -0,0 +1,70 @@
+<!DOCTYPE html>
+<meta charset="utf-8">
+<title>HTML: window.open `features`: tokenization -- size features `width` vs `innerwidth`</title>
+<meta name=timeout content=long>
+<link rel="help" href="https://html.spec.whatwg.org/multipage/#apis-for-creating-and-navigating-browsing-contexts-by-name">
+
+<!-- user agents are not required to support open features other than `noopener`
+     and on some platforms position and size features don't make sense -->
+<meta name="flags" content="may" />
+
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="/common/PrefixedPostMessage.js"></script>
+<script>
+var windowURL = 'resources/message-opener.html';
+var featuresPrefix = `top=0,left=0,height=401,`;
+
+setup (() => {
+  // Before running tests, open a window using features that mimic
+  // what would happen if the feature tested here were set to 0
+  // for comparison later.
+  var featureString = `${featuresPrefix}width=0`;
+  var prefixedMessage = new PrefixedMessageTest();
+  prefixedMessage.onMessage((data, e) => {
+    e.source.close();
+    runWindowTests(data);
+  });
+  var win = window.open(prefixedMessage.url(windowURL), '', featureString);
+});
+
+function runWindowTests (baselineDimensions) {
+
+  // The last specified feature is used
+  [ 'width=401,width=402',
+    'width=401,innerwidth=402',
+    'innerwidth=401,width=402',
+    'innerwidth=401,innerwidth=402',
+  ].forEach((features, idx, arr) => {
+    async_test(t => {
+      var prefixedMessage = new PrefixedMessageTest();
+      prefixedMessage.onMessage(t.step_func_done((data, e) => {
+        e.source.close();
+        assert_equals(data.width, 402);
+      }));
+      var win = window.open(prefixedMessage.url(windowURL), '', featuresPrefix + features);
+    }, `${format_value(features)} repeated width/innerwidth features`);
+  });
+
+  // The last specified feature is used even if the value is 0 or error
+  [ 'width=401,width=0',
+    'width=401,innerwidth=0',
+    'innerwidth=401,width=0',
+    'innerwidth=401,innerwidth=0',
+    'width=401,width=error',
+    'width=401,innerwidth=error',
+    'innerwidth=401,width=error',
+    'innerwidth=401,innerwidth=error',
+  ].forEach((features, idx, arr) => {
+    async_test(t => {
+      var prefixedMessage = new PrefixedMessageTest();
+      prefixedMessage.onMessage(t.step_func_done((data, e) => {
+        e.source.close();
+        assert_equals(data.width, baselineDimensions.width);
+      }));
+      var win = window.open(prefixedMessage.url(windowURL), '', featuresPrefix + features);
+    }, `${format_value(features)} repeated width/innerwidth features where the last one is 0 or error`);
+  });
+}
+
+</script>
