diff --git a/testing/web-platform/tests/storage/estimate-usage-details-application-cache.https.tentative.html b/testing/web-platform/tests/storage/estimate-usage-details-application-cache.https.tentative.html
new file mode 100644
index 000000000000..464a99887bdb
--- /dev/null
+++ b/testing/web-platform/tests/storage/estimate-usage-details-application-cache.https.tentative.html
@@ -0,0 +1,29 @@
+<!doctype html>
+<html>
+<title>Quota Estimate: usage details reflect application cache changes.</title>
+<meta charset='utf-8'>
+<link rel='author' href='jarrydg@chromium.org' title='Jarryd Goodman'>
+<script src='/resources/testharness.js'></script>
+<script src='/resources/testharnessreport.js'></script>
+<script src='../cookie-store/resources/helpers.js'></script>
+<script>
+'use strict';
+
+promise_test(async t => {
+  let estimate = await navigator.storage.estimate();
+
+  const usageBeforeCreate = estimate.usageDetails.applicationCache || 0;
+
+  const iframe = await
+      createIframe('./resources/iframe_with_appcache_manifest.html', t);
+  await waitForMessage();
+
+  estimate = await navigator.storage.estimate();
+  assert_true('applicationCache' in estimate.usageDetails);
+  const usageAfterCreate = estimate.usageDetails.applicationCache;
+
+  assert_greater_than(
+      usageAfterCreate, usageBeforeCreate);
+}, 'estimate() shows usage increase after app is cached');
+</script>
+</html>
diff --git a/testing/web-platform/tests/storage/estimate-usage-details-caches.https.tentative.any.js b/testing/web-platform/tests/storage/estimate-usage-details-caches.https.tentative.any.js
new file mode 100644
index 000000000000..bf889f84184f
--- /dev/null
+++ b/testing/web-platform/tests/storage/estimate-usage-details-caches.https.tentative.any.js
@@ -0,0 +1,20 @@
+// META: title=StorageManager: estimate() for caches
+
+promise_test(async t => {
+  let estimate = await navigator.storage.estimate();
+
+  const cachesUsageBeforeCreate = estimate.usageDetails.caches || 0;
+
+  const cacheName = 'testCache';
+  const cache = await caches.open(cacheName);
+  t.add_cleanup(() => caches.delete(cacheName));
+
+  await cache.put('/test.json', new Response('x'.repeat(1024*1024)));
+
+  estimate = await navigator.storage.estimate();
+  assert_true('caches' in estimate.usageDetails);
+  const cachesUsageAfterPut = estimate.usageDetails.caches;
+  assert_greater_than(
+      cachesUsageAfterPut, cachesUsageBeforeCreate,
+      'estimated usage should increase after value is stored');
+}, 'estimate() shows usage increase after large value is stored');
diff --git a/testing/web-platform/tests/storage/estimate-usage-details.https.tentative.any.js b/testing/web-platform/tests/storage/estimate-usage-details.https.tentative.any.js
new file mode 100644
index 000000000000..2a1cea5fb8df
--- /dev/null
+++ b/testing/web-platform/tests/storage/estimate-usage-details.https.tentative.any.js
@@ -0,0 +1,12 @@
+// META: title=StorageManager: estimate() should have usage details
+
+promise_test(async t => {
+  const estimate = await navigator.storage.estimate();
+  assert_equals(typeof estimate, 'object');
+  assert_true('usage' in estimate);
+  assert_equals(typeof estimate.usage, 'number');
+  assert_true('quota' in estimate);
+  assert_equals(typeof estimate.quota, 'number');
+  assert_true('usageDetails' in estimate);
+  assert_equals(typeof estimate.usageDetails, 'object');
+}, 'estimate() resolves to dictionary with members, including usageDetails');
diff --git a/testing/web-platform/tests/storage/resources/appcache.manifest b/testing/web-platform/tests/storage/resources/appcache.manifest
new file mode 100644
index 000000000000..ce90bafd21fe
--- /dev/null
+++ b/testing/web-platform/tests/storage/resources/appcache.manifest
@@ -0,0 +1,3 @@
+CACHE MANIFEST
+# iframe_with_appcache_manifest.html references this manifest to get cached in
+# AppCache.
diff --git a/testing/web-platform/tests/storage/resources/iframe_with_appcache_manifest.html b/testing/web-platform/tests/storage/resources/iframe_with_appcache_manifest.html
new file mode 100644
index 000000000000..8365ce41f494
--- /dev/null
+++ b/testing/web-platform/tests/storage/resources/iframe_with_appcache_manifest.html
@@ -0,0 +1,17 @@
+<!doctype html>
+<html manifest="appcache.manifest">
+<title>Iframe that will be cached using application cache.</title>
+<meta charset='utf-8'>
+<link rel='author' href='jarrydg@chromium.org' title='Jarryd Goodman'>
+<script>
+(async () => {
+  const initPromise = new Promise(resolve => {
+    applicationCache.addEventListener('cached', resolve);
+    applicationCache.addEventListener('noupdate', resolve);
+  });
+  await initPromise;
+
+  window.parent.postMessage('document cached');
+})();
+</script>
+</html>
