diff --git a/css/css-conditional/container-queries/at-container-snapped-parsing.html b/css/css-conditional/container-queries/at-container-snapped-parsing.html
new file mode 100644
index 00000000000000..490c416a1ed8dc
--- /dev/null
+++ b/css/css-conditional/container-queries/at-container-snapped-parsing.html
@@ -0,0 +1,80 @@
+<!DOCTYPE html>
+<title>CSS Conditional Test: @container snapped query parsing</title>
+<link rel="help" href="https://drafts.csswg.org/css-conditional-5/#container-rule">
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="/css/css-conditional/container-queries/support/cq-testcommon.js"></script>
+<div style="container-name:name;container-type:scroll-state">
+  <main id="main"></main>
+</div>
+<script>
+  setup(() => assert_implements_container_queries());
+
+  function cleanup_main() {
+    while (main.firstChild)
+      main.firstChild.remove();
+  }
+
+  function set_style(text) {
+    let style = document.createElement('style');
+    style.innerText = text;
+    main.append(style);
+    return style;
+  }
+
+  function test_rule_valid(query) {
+    test(t => {
+      t.add_cleanup(cleanup_main);
+      let style = set_style(`@container ${query} {}`);
+      assert_equals(style.sheet.rules.length, 1);
+    }, query);
+  }
+
+  function test_condition_invalid(condition) {
+    test(t => {
+      t.add_cleanup(cleanup_main);
+      let style = set_style(`@container name ${condition} {}`);
+      assert_equals(style.sheet.rules.length, 0);
+    }, condition);
+  }
+
+  // Tests that 1) the condition parses, and 2) is either "unknown" or not, as
+  // specified.
+  function test_condition_valid(condition, unknown) {
+    test(t => {
+      t.add_cleanup(cleanup_main);
+      let style = set_style(`
+        @container name ${condition} {}
+        @container name (${condition}) or (not (${condition})) { main { --match:true; } }
+      `);
+      assert_equals(style.sheet.rules.length, 2);
+      const expected = unknown ? '' : 'true';
+      assert_equals(getComputedStyle(main).getPropertyValue('--match'), expected);
+    }, condition);
+  }
+
+  function test_condition_known(condition) {
+    test_condition_valid(condition, false /* unknown */);
+  }
+
+  function test_condition_unknown(condition) {
+    test_condition_valid(condition, true /* unknown */);
+  }
+
+  test_condition_known('scroll-state(snapped)');
+  test_condition_known('scroll-state(snapped: x)');
+  test_condition_known('scroll-state(snapped: y)');
+  test_condition_known('scroll-state(snapped: none)');
+  test_condition_known('scroll-state(snapped: block)');
+  test_condition_known('scroll-state(snapped: inline)');
+  test_condition_known('(scroll-state(snapped: block))');
+  test_condition_known('scroll-state((snapped: inline))');
+  test_condition_known('scroll-state(not ((snapped: inline) and (snapped: block)))');
+  test_condition_known('scroll-state((snapped: x) or (snapped: y))');
+
+  test_condition_unknown('scroll-state(snapped: auto)');
+  test_condition_unknown('scroll-state(snapped: true)');
+  test_condition_unknown('scroll-state(style(snapped: inline))');
+  test_condition_unknown('style(scroll-state(snapped: inline))');
+  test_condition_unknown('scroll-state(snapped:)');
+</script>
diff --git a/css/css-conditional/container-queries/at-container-snapped-serialization.html b/css/css-conditional/container-queries/at-container-snapped-serialization.html
new file mode 100644
index 00000000000000..59cc3d37f4f3fb
--- /dev/null
+++ b/css/css-conditional/container-queries/at-container-snapped-serialization.html
@@ -0,0 +1,32 @@
+<!DOCTYPE html>
+<title>CSS Container Queries: scroll-state(snapped) conditionText serialization</title>
+<link rel="help" href="https://drafts.csswg.org/css-conditional-5/#container-queries">
+<link rel="help" href="https://drafts.csswg.org/cssom/#serialize-a-css-rule">
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="/css/css-conditional/container-queries/support/cq-testcommon.js"></script>
+<style id="testSheet">
+  @container scroll-state(        snapped:inline) { }
+  @container scroll-STate(snapped:    ) { }
+  @container scroll-STate(snapped) { }
+  @container  scroll-state(  ( snapped: INLINE) OR ( SNAPPED: BlOCK  ) ) { }
+  @container scroll-state (snapped: inline) { }
+</style>
+<script>
+  setup(() => {
+    assert_implements_container_queries();
+    assert_equals(testSheet.sheet.cssRules.length, 5);
+  });
+
+  const tests = [
+      ["scroll-state(snapped: inline)", "Normalize spaces"],
+      ["scroll-STate(snapped:    )", "No value - invalid, serializes as <general-enclosed>"],
+      ["scroll-state(snapped)", "Boolean context"],
+      ["scroll-state((snapped: inline) or (snapped: block))", "Logical with 'or'"],
+      ["scroll-state (snapped: inline)", "Not a scroll-state function with space before '('"]
+  ].map((e, i) => [testSheet.sheet.cssRules[i], ...e]);
+
+  tests.forEach((t) => {
+    test(() => assert_equals(t[0].conditionText, t[1]), t[2]);
+  });
+</script>
diff --git a/css/css-conditional/container-queries/at-container-stuck-parsing.html b/css/css-conditional/container-queries/at-container-stuck-parsing.html
new file mode 100644
index 00000000000000..e2d305cbb826cf
--- /dev/null
+++ b/css/css-conditional/container-queries/at-container-stuck-parsing.html
@@ -0,0 +1,85 @@
+<!DOCTYPE html>
+<title>CSS Conditional Test: @container stuck query parsing</title>
+<link rel="help" href="https://drafts.csswg.org/css-conditional-5/#container-rule">
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="/css/css-conditional/container-queries/support/cq-testcommon.js"></script>
+<div style="container-name:name;container-type:scroll-state">
+  <main id="main"></main>
+</div>
+<script>
+  setup(() => assert_implements_container_queries());
+
+  function cleanup_main() {
+    while (main.firstChild)
+      main.firstChild.remove();
+  }
+
+  function set_style(text) {
+    let style = document.createElement('style');
+    style.innerText = text;
+    main.append(style);
+    return style;
+  }
+
+  function test_rule_valid(query) {
+    test(t => {
+      t.add_cleanup(cleanup_main);
+      let style = set_style(`@container ${query} {}`);
+      assert_equals(style.sheet.rules.length, 1);
+    }, query);
+  }
+
+  function test_condition_invalid(condition) {
+    test(t => {
+      t.add_cleanup(cleanup_main);
+      let style = set_style(`@container name ${condition} {}`);
+      assert_equals(style.sheet.rules.length, 0);
+    }, condition);
+  }
+
+  // Tests that 1) the condition parses, and 2) is either "unknown" or not, as
+  // specified.
+  function test_condition_valid(condition, unknown) {
+    test(t => {
+      t.add_cleanup(cleanup_main);
+      let style = set_style(`
+        @container name ${condition} {}
+        @container name (${condition}) or (not (${condition})) { main { --match:true; } }
+      `);
+      assert_equals(style.sheet.rules.length, 2);
+      const expected = unknown ? '' : 'true';
+      assert_equals(getComputedStyle(main).getPropertyValue('--match'), expected);
+    }, condition);
+  }
+
+  function test_condition_known(condition) {
+    test_condition_valid(condition, false /* unknown */);
+  }
+
+  function test_condition_unknown(condition) {
+    test_condition_valid(condition, true /* unknown */);
+  }
+
+  test_condition_known('scroll-state(stuck)');
+  test_condition_known('scroll-state(stuck: none)');
+  test_condition_known('scroll-state(stuck: top)');
+  test_condition_known('scroll-state(stuck: left)');
+  test_condition_known('scroll-state(stuck: bottom)');
+  test_condition_known('scroll-state(stuck: right)');
+  test_condition_known('scroll-state(stuck: block-start)');
+  test_condition_known('scroll-state(stuck: block-end)');
+  test_condition_known('scroll-state(stuck: inline-start)');
+  test_condition_known('scroll-state(stuck: inline-end)');
+  test_condition_known('(scroll-state(stuck: top))');
+  test_condition_known('scroll-state((stuck: top))');
+  test_condition_known('scroll-state(not ((stuck: top) and (stuck: bottom)))');
+  test_condition_known('scroll-state((stuck: right) or (stuck: left))');
+
+  test_condition_unknown('scroll-state(stuck: auto)');
+  test_condition_unknown('scroll-state(stuck: true)');
+  test_condition_unknown('scroll-state(style(stuck: top))');
+  test_condition_unknown('style(scroll-state(stuck: top))');
+  test_condition_unknown('scroll-state(stuck:)');
+  test_condition_unknown('scroll-state(--foo)');
+</script>
diff --git a/css/css-conditional/container-queries/at-container-stuck-serialization.html b/css/css-conditional/container-queries/at-container-stuck-serialization.html
new file mode 100644
index 00000000000000..d5abede45c25be
--- /dev/null
+++ b/css/css-conditional/container-queries/at-container-stuck-serialization.html
@@ -0,0 +1,32 @@
+<!DOCTYPE html>
+<title>CSS Container Queries: scroll-state(stuck) conditionText serialization</title>
+<link rel="help" href="https://drafts.csswg.org/css-conditional-5/#container-queries">
+<link rel="help" href="https://drafts.csswg.org/cssom/#serialize-a-css-rule">
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="/css/css-conditional/container-queries/support/cq-testcommon.js"></script>
+<style id="testSheet">
+  @container scroll-state(        stuck:top) { }
+  @container scroll-STate(stuck:    ) { }
+  @container scroll-STate(stuck) { }
+  @container  scroll-state(  ( stuck: BOTTOM) OR ( STUCK: inline-START  ) ) { }
+  @container scroll-state (stuck: top) { }
+</style>
+<script>
+  setup(() => {
+    assert_implements_container_queries();
+    assert_equals(testSheet.sheet.cssRules.length, 5);
+  });
+
+  const tests = [
+      ["scroll-state(stuck: top)", "Normalize spaces"],
+      ["scroll-STate(stuck:    )", "No value - invalid, serializes as <general-enclosed>"],
+      ["scroll-state(stuck)", "Boolean context"],
+      ["scroll-state((stuck: bottom) or (stuck: inline-start))", "Logical with 'or'"],
+      ["scroll-state (stuck: top)", "Not a scroll-state function with space before '('"]
+  ].map((e, i) => [testSheet.sheet.cssRules[i], ...e]);
+
+  tests.forEach((t) => {
+    test(() => assert_equals(t[0].conditionText, t[1]), t[2]);
+  });
+</script>
diff --git a/css/css-conditional/container-queries/container-type-scroll-state-computed.html b/css/css-conditional/container-queries/container-type-scroll-state-computed.html
new file mode 100644
index 00000000000000..4e80712beab2dc
--- /dev/null
+++ b/css/css-conditional/container-queries/container-type-scroll-state-computed.html
@@ -0,0 +1,16 @@
+<!DOCTYPE html>
+<meta charset="utf-8">
+<title>CSS Conditional Test: Computed values of container-type with scroll-state</title>
+<link rel="help" href="https://drafts.csswg.org/css-conditional-5/#container-type">
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="/css/support/computed-testcommon.js"></script>
+<script src="/css/css-conditional/container-queries/support/cq-testcommon.js"></script>
+<div id="target"></div>
+<script>
+  setup(() => assert_implements_container_queries());
+
+  test_computed_value('container-type', 'scroll-state');
+  test_computed_value('container-type', 'scroll-state size', 'size scroll-state');
+  test_computed_value('container-type', 'inline-size scroll-state');
+</script>
diff --git a/css/css-conditional/container-queries/container-type-scroll-state-containment.html b/css/css-conditional/container-queries/container-type-scroll-state-containment.html
new file mode 100644
index 00000000000000..cc1af5a08ebb14
--- /dev/null
+++ b/css/css-conditional/container-queries/container-type-scroll-state-containment.html
@@ -0,0 +1,34 @@
+<!DOCTYPE html>
+<title>CSS Container Queries: container type scroll-state</title>
+<link rel="help" href="https://drafts.csswg.org/css-conditional-5/#container-type">
+<link rel="help" href="https://github.com/w3c/csswg-drafts/issues/6402#issuecomment-1812973013">
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="/css/css-conditional/container-queries/support/cq-testcommon.js"></script>
+<style>
+  body { margin: 0; }
+  #container {
+    margin-top: 100px;
+    container-type: scroll-state;
+    width: fit-content;
+  }
+  #child {
+    margin-top: 100px;
+    width: 100px;
+    height: 100px;
+  }
+</style>
+<div id="container">
+  <div id="child">Non-zero-content</div>
+</div>
+<script>
+  test(() => {
+    assert_equals(container.offsetWidth, 100, "Intrinsically sized width");
+    assert_equals(container.offsetHeight, 100, "Intrinsically sized height");
+  }, "container-type:scroll-state does not apply size containment");
+
+  test(() => {
+    assert_equals(child.getBoundingClientRect().y, 100,
+                  "#container and #child margins collapsed");
+  }, "container-type:scroll-state does not establish a formatting context");
+</script>
diff --git a/css/css-conditional/container-queries/container-type-scroll-state-parsing.html b/css/css-conditional/container-queries/container-type-scroll-state-parsing.html
new file mode 100644
index 00000000000000..7f3779bc39d185
--- /dev/null
+++ b/css/css-conditional/container-queries/container-type-scroll-state-parsing.html
@@ -0,0 +1,20 @@
+<!DOCTYPE html>
+<meta charset="utf-8">
+<title>CSS Conditional Test: Parsing of container-type with scroll-state</title>
+<link rel="help" href="https://drafts.csswg.org/css-conditional-5/#container-type">
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="/css/support/parsing-testcommon.js"></script>
+<script src="/css/css-conditional/container-queries/support/cq-testcommon.js"></script>
+<div id="target"></div>
+<script>
+  setup(() => assert_implements_container_queries());
+
+  test_valid_value('container-type', 'scroll-state');
+  test_valid_value('container-type', 'size scroll-state');
+  test_valid_value('container-type', 'scroll-state inline-size', 'inline-size scroll-state');
+
+  test_invalid_value('container-type', 'scroll-state scroll-state');
+  test_invalid_value('container-type', 'normal scroll-state');
+  test_invalid_value('container-type', 'inline-size block-size scroll-state');
+</script>
diff --git a/css/css-conditional/container-queries/scroll-state-initially-snapped.html b/css/css-conditional/container-queries/scroll-state-initially-snapped.html
new file mode 100644
index 00000000000000..64a171c361e7c9
--- /dev/null
+++ b/css/css-conditional/container-queries/scroll-state-initially-snapped.html
@@ -0,0 +1,47 @@
+<!DOCTYPE html>
+<title>@container: scroll-state(snapped) matching for initial rendering</title>
+<link rel="help" href="https://drafts.csswg.org/css-conditional-5/#container-rule">
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="/css/css-conditional/container-queries/support/cq-testcommon.js"></script>
+<script src="/css/css-transitions/support/helper.js"></script>
+<style>
+  :root {
+    scroll-snap-type: block mandatory;
+  }
+  body {
+    margin: 0;
+  }
+  #filler-before {
+    height: 200px;
+  }
+  #filler-after {
+    height: 10000px;
+  }
+  #snapped {
+    container-name: initially-snapped;
+    container-type: scroll-state;
+    scroll-snap-align: start;
+    width: 100px;
+    height: 100px;
+    background: teal;
+  }
+
+  @container initially-snapped scroll-state(snapped: block) {
+    span { --snapped: yes }
+  }
+</style>
+<div id="filler-before"></div>
+<div id="snapped">
+  <span id="target">My container is snapped</span>
+</div>
+<div id="filler-after"></div>
+<script>
+  setup(() => assert_implements_container_queries());
+
+  promise_test(async t => {
+    await waitForAnimationFrames(2);
+    assert_equals(getComputedStyle(target).getPropertyValue("--snapped"), "yes");
+    assert_equals(document.documentElement.scrollTop, 200);
+  }, "Check that scroll-state(snapped: block) matches");
+</script>
diff --git a/css/css-conditional/container-queries/scroll-state-initially-stuck.html b/css/css-conditional/container-queries/scroll-state-initially-stuck.html
new file mode 100644
index 00000000000000..c0d59b61e768d7
--- /dev/null
+++ b/css/css-conditional/container-queries/scroll-state-initially-stuck.html
@@ -0,0 +1,34 @@
+<!DOCTYPE html>
+<title>@container: scroll-state(stuck) matching for initial rendering</title>
+<link rel="help" href="https://drafts.csswg.org/css-conditional-5/#container-rule">
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="/css/css-conditional/container-queries/support/cq-testcommon.js"></script>
+<script src="/css/css-transitions/support/helper.js"></script>
+<style>
+  #filler {
+    height: 10000px;
+  }
+  #stuck {
+    container-name: initially-stuck;
+    container-type: scroll-state;
+    position: sticky;
+    bottom: 0;
+  }
+
+  @container initially-stuck scroll-state(stuck: bottom) {
+    span { --stuck: yes }
+  }
+</style>
+<div id="filler"></div>
+<div id="stuck">
+  <span id="target">My container is stuck</span>
+</div>
+<script>
+  setup(() => assert_implements_container_queries());
+
+  promise_test(async t => {
+    await waitForAnimationFrames(2);
+    assert_equals(getComputedStyle(target).getPropertyValue("--stuck"), "yes");
+  }, "Check that scroll-state(stuck: bottom) matches");
+</script>
diff --git a/css/css-conditional/container-queries/scroll-state-snapped-change.html b/css/css-conditional/container-queries/scroll-state-snapped-change.html
new file mode 100644
index 00000000000000..6e9843b8b755b1
--- /dev/null
+++ b/css/css-conditional/container-queries/scroll-state-snapped-change.html
@@ -0,0 +1,55 @@
+<!DOCTYPE html>
+<title>@container: scroll-state(snapped) changed after scroll</title>
+<link rel="help" href="https://drafts.csswg.org/css-conditional-5/#container-rule">
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="/css/css-conditional/container-queries/support/cq-testcommon.js"></script>
+<script src="/css/css-transitions/support/helper.js"></script>
+<style>
+  :root {
+    scroll-snap-type: block mandatory;
+  }
+  body {
+    margin: 0;
+  }
+  #filler {
+    height: 10000px;
+  }
+  .snapped {
+    container-type: scroll-state;
+    scroll-snap-align: start;
+    width: 100px;
+    height: 100px;
+    margin-bottom: 100px;
+    background: teal;
+  }
+
+  @container scroll-state(snapped: block) {
+    span { --snapped: yes }
+  }
+</style>
+<div class="snapped">
+  <span id="target1"></span>
+</div>
+<div class="snapped">
+  <span id="target2"></span>
+</div>
+<div id="filler"></div>
+<script>
+  setup(() => assert_implements_container_queries());
+
+  promise_test(async t => {
+    await waitForAnimationFrames(2);
+    assert_equals(getComputedStyle(target1).getPropertyValue("--snapped"), "yes");
+    assert_equals(getComputedStyle(target2).getPropertyValue("--snapped"), "");
+    assert_equals(document.documentElement.scrollTop, 0);
+  }, "Check that scroll-state(snapped: block) matches on #target1 before scroll");
+
+  promise_test(async t => {
+    document.documentElement.scrollTop = 300;
+    await waitForAnimationFrames(2);
+    assert_equals(getComputedStyle(target1).getPropertyValue("--snapped"), "");
+    assert_equals(getComputedStyle(target2).getPropertyValue("--snapped"), "yes");
+    assert_equals(document.documentElement.scrollTop, 200);
+  }, "Check that scroll-state(snapped: block) matches on #target2 after scroll");
+</script>
diff --git a/css/css-conditional/container-queries/scroll-state-snapped-container-type-change.html b/css/css-conditional/container-queries/scroll-state-snapped-container-type-change.html
new file mode 100644
index 00000000000000..556e4c2445b3f3
--- /dev/null
+++ b/css/css-conditional/container-queries/scroll-state-snapped-container-type-change.html
@@ -0,0 +1,84 @@
+<!DOCTYPE html>
+<title>@container: scroll-state(snapped) property changes</title>
+<link rel="help" href="https://drafts.csswg.org/css-conditional-5/#container-rule">
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="/css/css-conditional/container-queries/support/cq-testcommon.js"></script>
+<script src="/css/css-transitions/support/helper.js"></script>
+<style>
+  :root {
+    scroll-snap-type: block mandatory;
+  }
+  body {
+    margin: 0;
+  }
+  #filler-before {
+    height: 200px;
+  }
+  #filler-after {
+    height: 10000px;
+  }
+  #snapped {
+    container-type: scroll-state;
+    scroll-snap-align: start;
+    width: 100px;
+    height: 100px;
+    background: teal;
+  }
+  span {
+    --snapped: no;
+    @container scroll-state(snapped) {
+      --snapped: yes;
+    }
+  }
+</style>
+<div id="filler-before"></div>
+<div id="snapped">
+  <span id="target">My container is snapped</span>
+</div>
+<div id="filler-after"></div>
+<script>
+  setup(() => assert_implements_container_queries());
+
+  promise_test(async t => {
+    await waitForAnimationFrames(2);
+    assert_equals(getComputedStyle(target).getPropertyValue("--snapped"), "yes");
+  }, "Check scroll-state(snapped) initially matching");
+
+  promise_test(async t => {
+    t.add_cleanup(async () => snapped.style.scrollSnapAlign = "");
+    snapped.style.scrollSnapAlign = "initial";
+    await waitForAnimationFrames(2);
+    assert_equals(getComputedStyle(target).getPropertyValue("--snapped"), "no",
+                  "scroll-snap-align removed");
+    snapped.style.scrollSnapAlign = "";
+    await waitForAnimationFrames(2);
+    assert_equals(getComputedStyle(target).getPropertyValue("--snapped"), "yes",
+                  "scroll-snap-align re-added");
+  }, "Check scroll-state(snapped) not matching when scroll-snap-align is removed");
+
+  promise_test(async t => {
+    t.add_cleanup(async () => document.documentElement.style.scrollSnapType = "");
+    document.documentElement.style.scrollSnapType = "initial";
+    await waitForAnimationFrames(2);
+    assert_equals(getComputedStyle(target).getPropertyValue("--snapped"), "no",
+                  "scroll-snap-type removed");
+    document.documentElement.style.scrollSnapType = "";
+    await waitForAnimationFrames(2);
+    assert_equals(getComputedStyle(target).getPropertyValue("--snapped"), "yes",
+                  "scroll-snap-type re-added");
+  }, "Check scroll-state(snapped) not matching when scroll-snap-type is removed");
+
+  promise_test(async t => {
+    t.add_cleanup(async () => snapped.style.containerType = "");
+    snapped.style.containerType = "initial";
+    await waitForAnimationFrames(2);
+    assert_equals(getComputedStyle(target).getPropertyValue("--snapped"), "no",
+                  "container-type removed");
+    snapped.style.containerType = "";
+    await waitForAnimationFrames(2);
+    assert_equals(getComputedStyle(target).getPropertyValue("--snapped"), "yes",
+                  "container-type re-added");
+  }, "Check scroll-state(snapped) not matching when container-type is removed");
+
+</script>
diff --git a/css/css-conditional/container-queries/scroll-state-snapped-snap-changing.html b/css/css-conditional/container-queries/scroll-state-snapped-snap-changing.html
new file mode 100644
index 00000000000000..161c2e1368dd2b
--- /dev/null
+++ b/css/css-conditional/container-queries/scroll-state-snapped-snap-changing.html
@@ -0,0 +1,67 @@
+<!DOCTYPE html>
+<title>@container: scroll-state(snapped) matches for scrollchanging</title>
+<link rel="help" href="https://drafts.csswg.org/css-conditional-5/#container-rule">
+<link rel="help" href="https://drafts.csswg.org/css-scroll-snap-2/#snap-events">
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="/resources/testdriver.js"></script>
+<script src="/resources/testdriver-actions.js"></script>
+<script src="/resources/testdriver-vendor.js"></script>
+<script src="/css/css-conditional/container-queries/support/cq-testcommon.js"></script>
+<script src="/css/css-transitions/support/helper.js"></script>
+<style>
+  html { scroll-snap-type: block mandatory; }
+  body { margin: 0; }
+  #filler { height: 10000px; }
+  .snapped {
+    container-type: scroll-state;
+    scroll-snap-align: start;
+    width: 100px;
+    height: 100px;
+  }
+  @container scroll-state(snapped: block) {
+    span { --snapped: true; }
+  }
+</style>
+<div id="snapped1" class="snapped">
+  <span id="target1"></span>
+</div>
+<div id="snapped2" class="snapped">
+  <span id="target2"></span>
+</div>
+<div id="filler"></div>
+<script>
+  setup(() => assert_implements_container_queries());
+
+  let changeTarget;
+  let changingTarget;
+
+  window.addEventListener("scrollsnapchange", e => changeTarget = e.snapTargetBlock);
+  window.addEventListener("scrollsnapchanging", e => changingTarget = e.snapTargetBlock);
+
+  promise_test(async t => {
+    await waitForAnimationFrames(2);
+    assert_equals(getComputedStyle(target1).getPropertyValue("--snapped"), "true");
+    assert_equals(getComputedStyle(target2).getPropertyValue("--snapped"), "");
+    assert_equals(changeTarget, snapped1, "snapchange has been called for #snapped1");
+    assert_equals(changingTarget, undefined, "snapchanging has not been called");
+    assert_equals(window.scrollY, 0);
+  }, "Initially snapped to #snapped1, scroll-state() styling #target1")
+
+  promise_test(async t => {
+    await new test_driver.Actions()
+        .addPointer("pointer1", "touch")
+        .pointerMove(0, 200, {origin: "viewport"})
+        .pointerDown()
+        .pause(50)
+        .pointerMove(0, 0, {origin: "viewport"})
+        .pause(50)
+        .send();
+    assert_equals(changeTarget, snapped1, "snapchange has not been called for #snapped2");
+    assert_equals(changingTarget, snapped2, "snapchanging has been called for #snapped2");
+    assert_equals(getComputedStyle(target1).getPropertyValue("--snapped"), "",
+                  "#target1 not matching scroll-state(snapped) while scrolling");
+    assert_equals(getComputedStyle(target2).getPropertyValue("--snapped"), "true",
+                  "#target2 matching scroll-state(snapped) while scrolling");
+  }, "scroll-state(snapped) matching #snapped2 while scrolling");
+</script>
diff --git a/css/css-conditional/container-queries/scroll-state-snapped-wm.html b/css/css-conditional/container-queries/scroll-state-snapped-wm.html
new file mode 100644
index 00000000000000..b6703e81142a3e
--- /dev/null
+++ b/css/css-conditional/container-queries/scroll-state-snapped-wm.html
@@ -0,0 +1,67 @@
+<!DOCTYPE html>
+<title>@container: scroll-state(snapped) matching for writing-mode</title>
+<link rel="help" href="https://drafts.csswg.org/css-conditional-5/#container-rule">
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="/css/css-conditional/container-queries/support/cq-testcommon.js"></script>
+<script src="/css/css-transitions/support/helper.js"></script>
+<style>
+  :root {
+    scroll-snap-type: block mandatory;
+  }
+  body {
+    margin: 0;
+  }
+  #filler-before {
+    height: 200px;
+  }
+  #filler-after {
+    height: 10000px;
+  }
+  #snapped {
+    writing-mode: vertical-lr;
+    container-name: initially-snapped;
+    container-type: scroll-state;
+    scroll-snap-align: start;
+    width: 100px;
+    height: 100px;
+    background: teal;
+  }
+
+  @container initially-snapped scroll-state(snapped: block) {
+    span { --snapped-logical: block }
+  }
+  @container initially-snapped scroll-state(snapped: inline) {
+    span { --snapped-logical: inline }
+  }
+  @container initially-snapped scroll-state(snapped: x) {
+    span { --snapped-physical: x }
+  }
+  @container initially-snapped scroll-state(snapped: y) {
+    span { --snapped-physical: y }
+  }
+</style>
+<div id="filler-before"></div>
+<div id="snapped">
+  <span id="target">My container is snapped</span>
+</div>
+<div id="filler-after"></div>
+<script>
+  setup(() => assert_implements_container_queries());
+
+  promise_test(async t => {
+    await waitForAnimationFrames(2);
+    assert_equals(getComputedStyle(target).getPropertyValue("--snapped-logical"), "inline");
+    assert_equals(getComputedStyle(target).getPropertyValue("--snapped-physical"), "y");
+    assert_equals(document.documentElement.scrollTop, 200);
+  }, "Check scroll-state(snapped) matching for vertical writing-mode");
+
+  promise_test(async t => {
+    snapped.style.writingMode = "horizontal-tb";
+    await waitForAnimationFrames(2);
+    assert_equals(getComputedStyle(target).getPropertyValue("--snapped-logical"), "block");
+    assert_equals(getComputedStyle(target).getPropertyValue("--snapped-physical"), "y");
+    assert_equals(document.documentElement.scrollTop, 200);
+  }, "Check scroll-state(snapped) matching dynamically changing to horizontal writing-mode");
+
+</script>
