diff --git a/css/selectors/invalidation/matches.html b/css/selectors/invalidation/is.html
similarity index 84%
rename from css/selectors/invalidation/matches.html
rename to css/selectors/invalidation/is.html
index 634ded3c7d760f6..0d905dcd4f6c479 100644
--- a/css/selectors/invalidation/matches.html
+++ b/css/selectors/invalidation/is.html
@@ -1,10 +1,10 @@
 <!DOCTYPE html>
 <html>
   <head>
-    <title>CSS Selectors Invalidation: :matches()</title>
+    <title>CSS Selectors Invalidation: :is()</title>
     <link rel="author" title="Victoria Su" href="mailto:victoriaytsu@google.com">
     <link rel="help" href="https://drafts.csswg.org/selectors-4/#matches">
-    <meta name="assert" content="This tests that the :matches() selector is effective">
+    <meta name="assert" content="This tests that the :is() selector is effective">
     <script src="/resources/testharness.js"></script>
     <script src="/resources/testharnessreport.js"></script>
     <style>
@@ -12,18 +12,18 @@
         color: yellow;
       }
       /*Simple selector arguments */
-      .a :matches(.b, .c) {
+      .a :is(.b, .c) {
         color: red;
       }
       /*Compound selector arguments */
-      .a :matches(.c#d, .e) {
+      .a :is(.c#d, .e) {
         color: green;
       }
       /* Complex selector arguments */
       .a .g>.b {
         color: black;
       }
-      .a :matches(.e+.f, .g>.b, .h) {
+      .a :is(.e+.f, .g>.b, .h) {
         color: blue;
       }
       .g>.b {
@@ -39,7 +39,7 @@
       .c>.a+.e {
         color: black;
       }
-      .a+:matches(.b+.f, :matches(.c>.e, .g)) {
+      .a+:is(.b+.f, :is(.c>.e, .g)) {
         color: red;
       }
       .c>.e {
@@ -108,32 +108,32 @@
         assert_equals(getComputedStyle(b1).color, red);
         assert_equals(getComputedStyle(b3).color, red);
         assert_equals(getComputedStyle(c1).color, red);
-      }, "Invalidate :matches() for simple selector arguments.");
+      }, "Invalidate :is() for simple selector arguments.");
 
       test(() => {
         a1.className = "a";
         assert_equals(getComputedStyle(d).color, green);
-      }, "Invalidate :matches() for compound selector arguments.");
+      }, "Invalidate :is() for compound selector arguments.");
 
       test(() => {
         a1.className = "a";
         assert_equals(getComputedStyle(b2).color, blue);
         assert_equals(getComputedStyle(b3).color, red);
         assert_equals(getComputedStyle(f1).color, blue);
-      }, "Invalidate :matches() for complex selector arguments.");
+      }, "Invalidate :is() for complex selector arguments.");
 
       test(() => {
         a1.className = "a";
         assert_equals(getComputedStyle(e2).color, black);
         a2.className = "a";
         assert_equals(getComputedStyle(e2).color, red);
-      }, "Invalidate nested :matches().");
+      }, "Invalidate nested :is().");
 
       test(() => {
         a1.className = "a";
         assert_equals(getComputedStyle(b2).color, blue);
         assert_equals(getComputedStyle(h1).color, black);
-      }, "Test specificity of :matches().");
+      }, "Test specificity of :is().");
     </script>
   </body>
 </html>
\ No newline at end of file
diff --git a/css/selectors/invalidation/where.html b/css/selectors/invalidation/where.html
index 1c6432f46eb4f2b..170398300f0b435 100644
--- a/css/selectors/invalidation/where.html
+++ b/css/selectors/invalidation/where.html
@@ -33,7 +33,7 @@
       :where(.a>:where(.g+.h, .b)~.i) {
         color: blue;
       }
-      :where(:matches(.a~.h)) {
+      :where(:is(.a~.h)) {
         color: yellow;
       }
     </style>
diff --git a/css/selectors/matches-nested.html b/css/selectors/is-nested.html
similarity index 74%
rename from css/selectors/matches-nested.html
rename to css/selectors/is-nested.html
index b82d43d09017955..7c3973ae058edfc 100644
--- a/css/selectors/matches-nested.html
+++ b/css/selectors/is-nested.html
@@ -1,31 +1,31 @@
 <!DOCTYPE html>
 <html>
   <head>
-    <title>CSS Selectors: :matches()</title>
+    <title>CSS Selectors: :is()</title>
     <link rel="author" title="Victoria Su" href="mailto:victoriaytsu@google.com">
     <link rel="help" href="https://drafts.csswg.org/selectors-4/#matches">
-    <meta name="assert" content="This tests that the :matches() selector is effective when nested">
+    <meta name="assert" content="This tests that the :is() selector is effective when nested">
     <script src="/resources/testharness.js"></script>
     <script src="/resources/testharnessreport.js"></script>
     <style>
-      /* Testing that highest specificity is chosen for class outside of :matches() */
+      /* Testing that highest specificity is chosen for class outside of :is() */
       .a+.b+.c>.e+.d {
         color: black;
         font-size: 10px;
         width: 10px;
       }
-      .a+:matches(.b+.f, .b+:matches(*, .c>.e, .g, *))+.d {
+      .a+:is(.b+.f, .b+:is(*, .c>.e, .g, *))+.d {
         color: red;
         font-size: 20px;
       }
       .a+.b+.c>.e+.d {
         color: yellow;
       }
-      /* Testing specificty of a class within :matches() */
+      /* Testing specificty of a class within :is() */
       .a+.c>.e {
         color: black;
       }
-      .a+:matches(.b+.f, :matches(.c>.e, .g)) {
+      .a+:is(.b+.f, :is(.c>.e, .g)) {
         color: red;
       }
       .c>.e {
@@ -61,11 +61,11 @@
         assert_equals(getComputedStyle(d1).color, yellow);
         assert_equals(getComputedStyle(d1).fontSize, "20px");
         assert_equals(getComputedStyle(d1).width, "10px");
-      }, "Test nested :matches() chooses highest specificity for class outside :matches().");
+      }, "Test nested :is() chooses highest specificity for class outside :is().");
 
       test(() => {
         assert_equals(getComputedStyle(e1).color, red);
-      }, "Test nested :matches() specificity for class within arguments.");
+      }, "Test nested :is() specificity for class within arguments.");
 
     </script>
   </body>
diff --git a/css/selectors/matches-specificity.html b/css/selectors/is-specificity.html
similarity index 76%
rename from css/selectors/matches-specificity.html
rename to css/selectors/is-specificity.html
index 41d7251a3d74efb..bf3dbc6bb9fc105 100644
--- a/css/selectors/matches-specificity.html
+++ b/css/selectors/is-specificity.html
@@ -1,10 +1,10 @@
 <!DOCTYPE html>
 <html>
   <head>
-    <title>CSS Selectors: :matches()</title>
+    <title>CSS Selectors: :is()</title>
     <link rel="author" title="Victoria Su" href="mailto:victoriaytsu@google.com">
     <link rel="help" href="https://drafts.csswg.org/selectors-4/#matches">
-    <meta name="assert" content="This tests that the :matches() selector chooses the correct specificity">
+    <meta name="assert" content="This tests that the :is() selector chooses the correct specificity">
     <script src="/resources/testharness.js"></script>
     <script src="/resources/testharnessreport.js"></script>
     <style>
@@ -13,7 +13,7 @@
         height: 10px;
         width: 10px;
       }
-      :matches(.a, .b.c + .d, .e) + :matches(* + .p, .q.r + .s, * + .t) + #target {
+      :is(.a, .b.c + .d, .e) + :is(* + .p, .q.r + .s, * + .t) + #target {
         height: 20px;
         width: 20px;
       }
@@ -34,7 +34,7 @@
         assert_equals(getComputedStyle(target).width, "30px");
         assert_equals(getComputedStyle(target).height, "20px");
         assert_equals(getComputedStyle(target).fontSize, "10px");
-      }, "Test :matches() uses highest possible specificity");
+      }, "Test :is() uses highest possible specificity");
 
     </script>
   </body>
