diff --git a/service-workers/service-worker/resources/scope1/redirect.py b/service-workers/service-worker/resources/scope1/redirect.py
new file mode 100644
index 00000000000000..0663ca0ed04d90
--- /dev/null
+++ b/service-workers/service-worker/resources/scope1/redirect.py
@@ -0,0 +1,5 @@
+import os
+import sys
+# Use the file from the parent directory.
+sys.path.append(os.path.dirname(os.path.dirname(__file__)))
+from redirect import main
diff --git a/service-workers/service-worker/resources/scope2/worker_interception_redirect_webworker.py b/service-workers/service-worker/resources/scope2/worker_interception_redirect_webworker.py
new file mode 100644
index 00000000000000..99db1343bad2a8
--- /dev/null
+++ b/service-workers/service-worker/resources/scope2/worker_interception_redirect_webworker.py
@@ -0,0 +1,5 @@
+import os
+import sys
+# Use the file from the parent directory.
+sys.path.append(os.path.dirname(os.path.dirname(__file__)))
+from worker_interception_redirect_webworker import main
diff --git a/service-workers/service-worker/resources/worker-interception-redirect-serviceworker.js b/service-workers/service-worker/resources/worker-interception-redirect-serviceworker.js
new file mode 100644
index 00000000000000..b815442fd3c5b9
--- /dev/null
+++ b/service-workers/service-worker/resources/worker-interception-redirect-serviceworker.js
@@ -0,0 +1,39 @@
+let name;
+if (self.registration.scope.indexOf('scope1') != -1)
+  name = 'sw1';
+if (self.registration.scope.indexOf('scope2') != -1)
+  name = 'sw2';
+
+
+self.addEventListener('fetch', evt => {
+  // There are three types of requests this service worker handles.
+
+  // (1) The first request for the worker, which will redirect elsewhere.
+  // "redirect.py" means to test network redirect, so let network handle it.
+  if (evt.request.url.indexOf('redirect.py') != -1) {
+    return;
+  }
+  // "sw-redirect" means to test service worker redirect, so respond with a
+  // redirect.
+  if (evt.request.url.indexOf('sw-redirect') != -1) {
+    const url = new URL(evt.request.url);
+    const redirect_to = url.searchParams.get('Redirect');
+    evt.respondWith(Response.redirect(redirect_to));
+    return;
+  }
+
+  // (2) After redirect, the request is for a "webworker.py" URL.
+  // Add a search parameter to indicate this service worker handled the
+  // final request for the worker.
+  if (evt.request.url.indexOf('webworker.py') != -1) {
+    const greeting = encodeURIComponent(`${name} saw the request for the worker script`);
+    evt.respondWith(fetch(`worker_interception_redirect_webworker.py?greeting=${greeting}`));
+    return;
+  }
+
+  // (3) The worker does a fetch() to simple.txt. Indicate that this service
+  // worker handled the request.
+  if (evt.request.url.indexOf('simple.txt') != -1) {
+    evt.respondWith(new Response(`${name} saw the fetch from the worker`));
+  }
+});
diff --git a/service-workers/service-worker/resources/worker-interception-redirect-webworker.js b/service-workers/service-worker/resources/worker-interception-redirect-webworker.js
new file mode 100644
index 00000000000000..7863af70d7835e
--- /dev/null
+++ b/service-workers/service-worker/resources/worker-interception-redirect-webworker.js
@@ -0,0 +1,30 @@
+// This is the (shared or dedicated) worker file for the
+// worker-interception-redirect test. It should be served by the corresponding
+// .py file instead of being served directly.
+//
+// This file is served from both resources/*webworker.py and
+// resources/scope2/*webworker.py, hence some of the complexity
+// below about paths.
+const resources_url = new URL("/service-workers/service-worker/resources/",
+                              self.location);
+
+// This greeting text is meant to be injected by the Python script that serves
+// this file, to indicate how the script was served (from network or from
+// service worker).
+//
+// We can't just use a sub pipe and name this file .sub.js since we want
+// to serve the file from multiple URLs (see above).
+let greeting = '%GREETING_TEXT%';
+if (!greeting)
+  greeting = 'the shared worker script was served from network';
+
+self.onconnect = async function(e) {
+  const port = e.ports[0];
+  port.start();
+  port.postMessage(greeting);
+
+  const fetch_url = new URL('simple.txt', resources_url);
+  const response = await fetch(fetch_url);
+  const text = await response.text();
+  port.postMessage('fetch(): ' + text);
+};
diff --git a/service-workers/service-worker/resources/worker_interception_redirect_webworker.py b/service-workers/service-worker/resources/worker_interception_redirect_webworker.py
new file mode 100644
index 00000000000000..e388e461448f64
--- /dev/null
+++ b/service-workers/service-worker/resources/worker_interception_redirect_webworker.py
@@ -0,0 +1,19 @@
+# This serves the worker JavaScript file. It takes a |greeting| request
+# parameter to inject into the JavaScript to indicate how the request
+# reached the server.
+import os
+import sys
+
+def main(request, response):
+  path = os.path.join(os.path.dirname(__file__),
+                      "worker-interception-redirect-webworker.js")
+  body = open(path, "rb").read()
+  if "greeting" in request.GET:
+    body = body.replace("%GREETING_TEXT%", request.GET["greeting"])
+  else:
+    body = body.replace("%GREETING_TEXT%", "")
+
+  headers = []
+  headers.append(("Content-Type", "text/javascript"))
+
+  return headers, body
diff --git a/service-workers/service-worker/worker-interception-redirect.https.html b/service-workers/service-worker/worker-interception-redirect.https.html
new file mode 100644
index 00000000000000..4e79eac1adb81e
--- /dev/null
+++ b/service-workers/service-worker/worker-interception-redirect.https.html
@@ -0,0 +1,169 @@
+<!DOCTYPE html>
+<title>Service Worker: controlling a SharedWorker</title>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="resources/test-helpers.sub.js"></script>
+<body>
+<script>
+// This tests service worker interception for worker clients, when the request
+// for the worker script goes through redirects. For example, a request can go
+// through a chain of URLs like A -> B -> C -> D and each URL might fall in the
+// scope of a different service worker, if any.
+// The two key questions are:
+// 1. Upon a redirect from A -> B, should a service worker for scope B
+//    intercept the request?
+// 2. After the final response, which service worker controls the resulting
+//    client?
+//
+// The standard prescribes the following:
+// 1. The service worker for scope B intercepts the redirect. *However*, once a
+//    request falls back to network (i.e., a service worker did not call
+//    respondWith()) and a redirect is then received from network, no service
+//    worker should intercept that redirect or any subsequent redirects.
+// 2. The final service worker that got a fetch event (or would have, in the
+//    case of a non-fetch-event worker) becomes the controller of the client.
+//
+// The standard may change later, see:
+// https://github.com/w3c/ServiceWorker/issues/1289
+//
+// The basic test setup is:
+// 1. Page registers service workers for scope1 and scope2.
+// 2. Page requests a worker from scope1.
+// 3. The request is redirected to scope2 or out-of-scope.
+// 4. The worker posts message to the page describing where the final response
+//   was served from (service worker or network).
+// 5. The worker does a fetch(), and posts back the response, which describes
+//   where the fetch response was served from.
+//
+// Currently this only tests shared worker but dedicated worker tests should be
+// added in a future patch.
+
+// Globals for easier cleanup.
+const scope1 = 'resources/scope1';
+const scope2 = 'resources/scope2';
+let frame;
+
+function get_message_from_worker(worker) {
+  return new Promise(resolve => {
+      worker.port.onmessage = evt => {
+        resolve(evt.data);
+      }
+    });
+}
+
+async function cleanup() {
+  if (frame)
+    frame.remove();
+
+  const reg1 = await navigator.serviceWorker.getRegistration(scope1);
+  if (reg1)
+    await reg1.unregister();
+  const reg2 = await navigator.serviceWorker.getRegistration(scope2);
+  if (reg2)
+    await reg2.unregister();
+}
+
+// Builds the worker script URL, which encodes information about where
+// to redirect to. The URL falls in sw1's scope.
+//
+// - |redirector| is "network" or "serviceworker". If "serviceworker", sw1 will
+// respondWith() a redirect. Otherwise, it falls back to network and the server
+// responds with a redirect.
+// - |redirect_location| is "scope2" or "out-of-scope". If "scope2", the
+// redirect ends up in sw2's scope2. Otherwise it's out of scope.
+function build_worker_url(redirector, redirect_location) {
+  let redirect_path;
+  // Set path to redirect.py, a file on the server that serves
+  // a redirect. When sw1 sees this URL, it falls back to network.
+  if (redirector == 'network')
+    redirector_path = 'redirect.py';
+  // Set path to 'sw-redirect', to tell the service worker
+  // to respond with redirect.
+  else if (redirector == 'serviceworker')
+    redirector_path = 'sw-redirect';
+
+  let redirect_to = base_path() + 'resources/';
+  // Append "scope2/" to redirect_to, so the redirect falls in scope2.
+  // Otherwise no change is needed, as the parent "resources/" directory is
+  // used, and is out-of-scope.
+  if (redirect_location == 'scope2')
+    redirect_to += 'scope2/';
+  // Append the name of the file which serves the worker script.
+  redirect_to += 'worker_interception_redirect_webworker.py';
+
+  return `scope1/${redirector_path}?Redirect=${redirect_to}`
+}
+
+promise_test(async t => {
+  await cleanup();
+  const service_worker = 'resources/worker-interception-redirect-serviceworker.js';
+  const registration1 = await navigator.serviceWorker.register(service_worker, {scope: scope1});
+  await wait_for_state(t, registration1.installing, 'activated');
+  const registration2 = await navigator.serviceWorker.register(service_worker, {scope: scope2});
+  await wait_for_state(t, registration2.installing, 'activated');
+
+  promise_test(t => {
+    return cleanup();
+  }, 'cleanup global state');
+}, 'initialize global state');
+
+function worker_redirect_test(worker_url,
+                              expected_main_resource_message,
+                              expected_subresource_message,
+                              description) {
+  promise_test(async t => {
+    // Create a frame to load the worker from. This way we can remove the frame
+    // to destroy the worker client when the test is done.
+    frame = await with_iframe('resources/blank.html');
+    t.add_cleanup(() => { frame.remove(); });
+
+    // Start the worker.
+    const w = new frame.contentWindow.SharedWorker(worker_url);
+    w.port.start();
+
+    // Expect a message from the worker indicating which service worker
+    // provided the response for the worker script request, if any.
+    const data = await get_message_from_worker(w);
+    assert_equals(data, expected_main_resource_message);
+
+    // The worker does a fetch() after it starts up. Expect a message from the
+    // worker indicating which service worker provided the response for the
+    // fetch(), if any.
+    //
+    // Note: for some reason, Firefox would pass all these tests if a
+    // postMessage ping/pong step is added before the fetch(). I.e., if the
+    // page does postMessage() and the worker does fetch() in response to the
+    // ping, the fetch() is properly intercepted. See
+    // https://bugzilla.mozilla.org/show_bug.cgi?id=1452528. (Chrome can't pass
+    // the tests either way.)
+    const message = get_message_from_worker(w);
+    const data2 = await message;
+    assert_equals(data2, expected_subresource_message);
+  }, description);
+}
+
+worker_redirect_test(
+    build_worker_url('network', 'scope2'),
+    'the shared worker script was served from network',
+    'fetch(): sw1 saw the fetch from the worker',
+    'request to sw1 scope gets network redirect to sw2 scope');
+
+worker_redirect_test(
+    build_worker_url('network', 'out-scope'),
+    'the shared worker script was served from network',
+    'fetch(): sw1 saw the fetch from the worker',
+    'request to sw1 scope gets network redirect to out-of-scope');
+
+worker_redirect_test(
+    build_worker_url('serviceworker', 'scope2'),
+    'sw2 saw the request for the worker script',
+    'fetch(): sw2 saw the fetch from the worker',
+    'request to sw1 scope gets service-worker redirect to sw2 scope');
+
+worker_redirect_test(
+    build_worker_url('serviceworker', 'out-scope'),
+    'the shared worker script was served from network',
+    'fetch(): sw1 saw the fetch from the worker',
+    'request to sw1 scope gets service-worker redirect to out-of-scope');
+</script>
+</body>