diff --git a/html/browsers/the-window-object/apis-for-creating-and-navigating-browsing-contexts-by-name/open-features-tokenization-001.html b/html/browsers/the-window-object/apis-for-creating-and-navigating-browsing-contexts-by-name/open-features-tokenization-001.html
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+++ b/html/browsers/the-window-object/apis-for-creating-and-navigating-browsing-contexts-by-name/open-features-tokenization-001.html
@@ -0,0 +1,148 @@
+<!DOCTYPE html>
+<meta charset="utf-8">
+<title>HTML: window.open `features`: tokenization -- `noopener`</title>
+<link rel="help" href="https://html.spec.whatwg.org/multipage/#apis-for-creating-and-navigating-browsing-contexts-by-name">
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script>
+var windowURL = 'resources/close-self.html';
+
+// Tests for how windows features are tokenized into 'name', 'value'
+// window features separators are ASCII whitespace, '=' and  ','
+
+test (t => {
+  // Tokenizing `name`: initial window features separators are ignored
+  // Each of these variants should tokenize to ('noopener', '')
+  var featureVariants = [
+    ' noopener',
+    '=noopener',
+    ',,noopener',
+    ',=, noopener',
+    '\n=noopener=',
+    '\tnoopener',
+    '\r,,,=noopener',
+    '\u000Cnoopener'
+  ];
+  featureVariants.forEach(feature => {
+    var win = window.open(windowURL, '', feature);
+    assert_equals(win, null, `"${feature}" should activate feature "noopener"`);
+  });
+}, 'tokenization should skip window features separators before `name`');
+
+test (t => {
+  // Tokenizing `name`: lowercase conversion
+  // Each of these variants should tokenize as feature ('noopener', '')
+  // except where indicated
+  // Note also that `value` is lowercased during tokenization
+  var featureVariants = [
+    'NOOPENER',
+    'noOpenER',
+    '  NOopener',
+    '=NOOPENER',
+    'noopener=NOOPENER', // => ('noopener', 'noopener')
+    'NOOPENER=noopener' // => ('noopener', 'noopener')
+  ];
+  featureVariants.forEach(feature => {
+    var win = window.open(windowURL, '', feature);
+    assert_equals(win, null, `"${feature}" should activate feature "noopener"`);
+  });
+}, 'feature `name` should be converted to ASCII lowercase');
+
+test (t => {
+  // After `name` has been collected, ignore any window features separators until '='
+  // except ',' OR a non-window-features-separator — break in those cases
+  // i.e. ignore whitespace until '=' unless a ',' is encountered first
+  // Each of these variants should tokenize as feature ('noopener', '')
+  var featureVariants = [
+    'noopener',
+    ' noopener\r',
+    'noopener\n =',
+    'noopener,',
+    'noopener  =,',
+    ', noopener   =',
+    'noopener,=',
+    'noopener foo', // => ('noopener', ''), ('foo', '')
+    'foo noopener=1', // => ('foo', ''), ('noopener', '1')
+    'foo=\u000Cnoopener' // => ('foo', ''), ('noopener', '')
+  ];
+  featureVariants.forEach(feature => {
+    var win = window.open(windowURL, '', feature);
+    assert_equals(win, null, `"${feature}" should activate feature "noopener"`);
+  });
+}, 'after `name`, tokenization should skip window features separators that are not "=" or ","');
+
+test (t => {
+  // After initial '=', tokenizing should ignore all separators except ','
+  // before collecting `value`
+  // Each of these variants should tokenize as feature ('noopener', '')
+  // Except where indicated
+  var featureVariants = [
+    'noopener=  yes', // => ('noopener', 'yes')
+    'noopener==,',
+    'noopener=\n ,',
+    'noopener = \t ,',
+    'noopener\n=\r noopener,', // => ('noopener', 'noopener')
+    'noopener=,yes', // => ('noopener'), ('yes')
+    'noopener= foo=,', // => ('noopener', 'foo')
+    'noopener = \u000Cyes' // => ('noopener', 'yes')
+  ];
+  featureVariants.forEach(feature => {
+    var win = window.open(windowURL, '', feature);
+    assert_equals(win, null, `"${feature}" should activate feature "noopener"`);
+  });
+}, 'Tokenizing should ignore window feature separators except "," after initial "=" and before value');
+
+test (t => {
+  // Tokenizing `value` should collect any non-separator code points until first separator
+  var featureVariants = [
+    'noopener=noopener', // => ('noopener', 'noopener')
+    'noopener=yes', // => ('noopener', 'yes')
+    'noopener = yes ,', // => ('noopener', 'yes')
+    'noopener=\nyes  ,', // => ('noopener', 'yes')
+    'noopener=yes yes', // => ('noopener', 'yes'), ('yes', '')
+    'noopener=yes\ts', // => ('noopener', 'yes'), ('s', '')
+    'noopener==', // => ('noopener', '')
+    'noopener=0\n,', // => ('noopener', '0')
+    '==noopener===', // => ('noopener', '')
+    'noopener==\u000C' // => ('noopener', '')
+  ];
+  featureVariants.forEach(feature => {
+    var win = window.open(windowURL, '', feature);
+    assert_equals(win, null, `"${feature}" should set "noopener"`);
+  });
+}, 'Tokenizing should read characters until first window feature separator as `value`');
+
+test (t => {
+  // If tokenizedFeatures contains an entry with the key "noopener"...disown opener
+  // i.e. `value` should be irrelevant
+  var featureVariants = [
+    'noopener=false',
+    ',noopener=0, ',
+    'foo=bar,noopener=noopener,',
+    'noopener=true',
+    'noopener=foo\nbar\t'
+  ];
+  featureVariants.forEach(feature => {
+    var win = window.open(windowURL, '', feature);
+    assert_equals(win, null, `"${feature}" should activate feature "noopener"`);
+  });
+}, '"noopener" should be based on name (key), not value');
+
+test (t => {
+  var invalidFeatureVariants = [
+    '-noopener', //     => ('-noopener', '')
+    'NOOPENERRRR', //   => ('noopenerrr', '')
+    'noOpenErR', //     => ('noopenerr', '')
+    'no_opener', //     => ('no_opener', '')
+    ' no opener', //    => ('no', ''), ('opener', '')
+    'no\nopener', //    => ('no', ''), ('opener', '')
+    'no,opener', //     => ('no', ''), ('opener', '')
+    '\0noopener', //    => ('\0noopener', '')
+    'noopener\u0000=yes' // => ('noopener\0', 'yes')
+  ];
+  invalidFeatureVariants.forEach(feature => {
+    var win = window.open(windowURL, '', feature);
+    assert_not_equals(win, null, `"${feature}" should NOT activate feature "noopener"`);
+  });
+}, 'invalid feature names should not tokenize as "noopener"');
+</script>
diff --git a/html/browsers/the-window-object/apis-for-creating-and-navigating-browsing-contexts-by-name/resources/close-self.html b/html/browsers/the-window-object/apis-for-creating-and-navigating-browsing-contexts-by-name/resources/close-self.html
new file mode 100644
index 00000000000000..0c0cf9fc4911de
--- /dev/null
+++ b/html/browsers/the-window-object/apis-for-creating-and-navigating-browsing-contexts-by-name/resources/close-self.html
@@ -0,0 +1,3 @@
+<script>
+  window.close();
+</script>
