diff --git a/chrome/browser/about_flags.cc b/chrome/browser/about_flags.cc
index 6d08dbd85c87d0..909ab9555458a4 100644
--- a/chrome/browser/about_flags.cc
+++ b/chrome/browser/about_flags.cc
@@ -7480,6 +7480,11 @@ const FeatureEntry kFeatureEntries[] = {
      flag_descriptions::kExtensionsMenuAccessControlDescription, kOsDesktop,
      FEATURE_VALUE_TYPE(features::kExtensionsMenuAccessControl)},
 
+    {"persistent-quota-is-temporary-quota",
+     flag_descriptions::kPersistentQuotaIsTemporaryQuotaName,
+     flag_descriptions::kPersistentQuotaIsTemporaryQuotaDescription, kOsAll,
+     FEATURE_VALUE_TYPE(blink::features::kPersistentQuotaIsTemporaryQuota)},
+
     // NOTE: Adding a new flag requires adding a corresponding entry to enum
     // "LoginCustomFlags" in tools/metrics/histograms/enums.xml. See "Flag
     // Histograms" in tools/metrics/histograms/README.md (run the
diff --git a/chrome/browser/flag-metadata.json b/chrome/browser/flag-metadata.json
index 042ef3fcbb9d0b..69235ac69b5f02 100644
--- a/chrome/browser/flag-metadata.json
+++ b/chrome/browser/flag-metadata.json
@@ -4421,6 +4421,11 @@
     "owners": [ "elklm", "engedy"],
     "expiry_milestone": 100
   },
+  {
+    "name": "persistent-quota-is-temporary-quota",
+    "owners": [ "mek", "cfredric" ],
+    "expiry_milestone": 100
+  },
   {
     "name": "photo-picker-video-support",
     "owners": [ "finnur" ],
diff --git a/chrome/browser/flag_descriptions.cc b/chrome/browser/flag_descriptions.cc
index dd5edbb92f9a5e..8f16c480151d11 100644
--- a/chrome/browser/flag_descriptions.cc
+++ b/chrome/browser/flag_descriptions.cc
@@ -2038,6 +2038,12 @@ const char kPermissionQuietChipDescription[] =
     "prompts. Requires chrome://flags/#quiet-notification-prompts to be "
     "enabled.";
 
+const char kPersistentQuotaIsTemporaryQuotaName[] =
+    "window.PERSISTENT is temporary quota.";
+const char kPersistentQuotaIsTemporaryQuotaDescription[] =
+    "Causes the window.PERSISTENT quota type to have the same semantics as "
+    "window.TEMPORARY.";
+
 const char kPlaybackSpeedButtonName[] = "Playback Speed Button";
 const char kPlaybackSpeedButtonDescription[] =
     "Enable the playback speed button on the media controls.";
diff --git a/chrome/browser/flag_descriptions.h b/chrome/browser/flag_descriptions.h
index c5107a62ac67d8..b50f698b725e17 100644
--- a/chrome/browser/flag_descriptions.h
+++ b/chrome/browser/flag_descriptions.h
@@ -1160,6 +1160,9 @@ extern const char kPermissionPredictionsDescription[];
 extern const char kPermissionQuietChipName[];
 extern const char kPermissionQuietChipDescription[];
 
+extern const char kPersistentQuotaIsTemporaryQuotaName[];
+extern const char kPersistentQuotaIsTemporaryQuotaDescription[];
+
 extern const char kPlaybackSpeedButtonName[];
 extern const char kPlaybackSpeedButtonDescription[];
 
diff --git a/storage/browser/file_system/file_system_quota_client.cc b/storage/browser/file_system/file_system_quota_client.cc
index 0e6e601ec18e16..195e2112faa9d8 100644
--- a/storage/browser/file_system/file_system_quota_client.cc
+++ b/storage/browser/file_system/file_system_quota_client.cc
@@ -4,12 +4,17 @@
 
 #include "storage/browser/file_system/file_system_quota_client.h"
 
+#include <numeric>
 #include <string>
 #include <utility>
 #include <vector>
 
+#include "base/barrier_callback.h"
+#include "base/barrier_closure.h"
 #include "base/bind.h"
 #include "base/check.h"
+#include "base/containers/span.h"
+#include "base/feature_list.h"
 #include "base/files/file.h"
 #include "base/location.h"
 #include "base/sequence_checker.h"
@@ -18,6 +23,7 @@
 #include "storage/browser/file_system/file_system_context.h"
 #include "storage/common/file_system/file_system_types.h"
 #include "storage/common/file_system/file_system_util.h"
+#include "third_party/blink/public/common/features.h"
 #include "third_party/blink/public/common/storage_key/storage_key.h"
 #include "third_party/blink/public/mojom/quota/quota_types.mojom.h"
 #include "url/origin.h"
@@ -26,6 +32,14 @@ namespace storage {
 
 namespace {
 
+static const FileSystemType kTemporaryAndPersistent[] = {
+    kFileSystemTypeTemporary,
+    kFileSystemTypePersistent,
+};
+static const FileSystemType kTemporary[] = {kFileSystemTypeTemporary};
+static const FileSystemType kPersistent[] = {kFileSystemTypePersistent};
+static const FileSystemType kSyncable[] = {kFileSystemTypeSyncable};
+
 std::vector<blink::StorageKey> ToStorageKeys(
     const std::vector<url::Origin>& origins) {
   std::vector<blink::StorageKey> storage_keys;
@@ -35,13 +49,53 @@ std::vector<blink::StorageKey> ToStorageKeys(
   return storage_keys;
 }
 
-std::vector<blink::StorageKey> GetStorageKeysForTypeOnFileTaskRunner(
-    FileSystemContext* context,
+template <typename T>
+std::vector<T> MergeWithoutDuplicates(const std::vector<std::vector<T>>& tss) {
+  if (tss.size() == 1) {
+    // We assume that each vector contains no duplicates, already.
+    return tss[0];
+  }
+  std::vector<T> merged;
+  merged.reserve(std::accumulate(
+      tss.begin(), tss.end(), 0U,
+      [](size_t acc, const std::vector<T>& ts) { return acc + ts.size(); }));
+  for (const auto& ts : tss) {
+    merged.insert(merged.end(), ts.begin(), ts.end());
+  }
+  base::ranges::sort(merged);
+  merged.erase(base::ranges::unique(merged), merged.end());
+  return merged;
+}
+
+// Converts StorageType to the FileSystemTypes that are used for that quota
+// type.
+base::span<const FileSystemType> QuotaStorageTypeToFileSystemTypes(
     blink::mojom::StorageType storage_type) {
-  FileSystemType type =
-      FileSystemQuotaClient::QuotaStorageTypeToFileSystemType(storage_type);
-  DCHECK(type != kFileSystemTypeUnknown);
+  using StorageType = blink::mojom::StorageType;
+
+  if (base::FeatureList::IsEnabled(
+          blink::features::kPersistentQuotaIsTemporaryQuota)) {
+    DCHECK_NE(storage_type, StorageType::kPersistent);
+    if (storage_type == StorageType::kTemporary)
+      return kTemporaryAndPersistent;
+  }
+  switch (storage_type) {
+    case StorageType::kTemporary:
+      return kTemporary;
+    case StorageType::kPersistent:
+      return kPersistent;
+    case StorageType::kSyncable:
+      return kSyncable;
+    case StorageType::kQuotaNotManaged:
+    case StorageType::kUnknown:
+      NOTREACHED();
+      return {};
+  }
+}
 
+std::vector<blink::StorageKey> GetStorageKeysForTypeOnFileTaskRunner(
+    FileSystemContext* context,
+    FileSystemType type) {
   FileSystemQuotaUtil* quota_util = context->GetQuotaUtil(type);
   if (!quota_util)
     return {};
@@ -50,12 +104,8 @@ std::vector<blink::StorageKey> GetStorageKeysForTypeOnFileTaskRunner(
 
 std::vector<blink::StorageKey> GetStorageKeysForHostOnFileTaskRunner(
     FileSystemContext* context,
-    blink::mojom::StorageType storage_type,
+    FileSystemType type,
     const std::string& host) {
-  FileSystemType type =
-      FileSystemQuotaClient::QuotaStorageTypeToFileSystemType(storage_type);
-  DCHECK(type != kFileSystemTypeUnknown);
-
   FileSystemQuotaUtil* quota_util = context->GetQuotaUtil(type);
   if (!quota_util)
     return {};
@@ -107,24 +157,31 @@ void FileSystemQuotaClient::GetStorageKeyUsage(
   DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
   DCHECK(!callback.is_null());
 
-  FileSystemType type =
-      FileSystemQuotaClient::QuotaStorageTypeToFileSystemType(storage_type);
-  DCHECK(type != kFileSystemTypeUnknown);
+  base::span<const FileSystemType> types =
+      QuotaStorageTypeToFileSystemTypes(storage_type);
 
-  FileSystemQuotaUtil* quota_util = file_system_context_->GetQuotaUtil(type);
-  if (!quota_util) {
-    std::move(callback).Run(0);
-    return;
-  }
+  base::RepeatingCallback<void(int64_t)> barrier =
+      base::BarrierCallback<int64_t>(
+          types.size(), base::BindOnce([](std::vector<int64_t> usages) {
+                          return std::accumulate(usages.begin(), usages.end(),
+                                                 0U);
+                        }).Then(std::move(callback)));
 
-  file_task_runner()->PostTaskAndReplyWithResult(
-      FROM_HERE,
-      // It is safe to pass Unretained(quota_util) since context owns it.
-      base::BindOnce(&FileSystemQuotaUtil::GetOriginUsageOnFileTaskRunner,
-                     base::Unretained(quota_util),
-                     base::RetainedRef(file_system_context_),
-                     storage_key.origin(), type),
-      std::move(callback));
+  for (auto type : types) {
+    FileSystemQuotaUtil* quota_util = file_system_context_->GetQuotaUtil(type);
+    if (quota_util) {
+      file_task_runner()->PostTaskAndReplyWithResult(
+          FROM_HERE,
+          // It is safe to pass Unretained(quota_util) since context owns it.
+          base::BindOnce(&FileSystemQuotaUtil::GetOriginUsageOnFileTaskRunner,
+                         base::Unretained(quota_util),
+                         base::RetainedRef(file_system_context_),
+                         storage_key.origin(), type),
+          barrier);
+    } else {
+      barrier.Run(0);
+    }
+  }
 }
 
 void FileSystemQuotaClient::GetStorageKeysForType(
@@ -133,11 +190,22 @@ void FileSystemQuotaClient::GetStorageKeysForType(
   DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
   DCHECK(!callback.is_null());
 
-  file_task_runner()->PostTaskAndReplyWithResult(
-      FROM_HERE,
-      base::BindOnce(&GetStorageKeysForTypeOnFileTaskRunner,
-                     base::RetainedRef(file_system_context_), storage_type),
-      std::move(callback));
+  base::span<const FileSystemType> types =
+      QuotaStorageTypeToFileSystemTypes(storage_type);
+
+  base::RepeatingCallback<void(std::vector<blink::StorageKey>)> barrier =
+      base::BarrierCallback<std::vector<blink::StorageKey>>(
+          types.size(),
+          base::BindOnce(&MergeWithoutDuplicates<blink::StorageKey>)
+              .Then(std::move(callback)));
+
+  for (auto type : types) {
+    file_task_runner()->PostTaskAndReplyWithResult(
+        FROM_HERE,
+        base::BindOnce(&GetStorageKeysForTypeOnFileTaskRunner,
+                       base::RetainedRef(file_system_context_), type),
+        barrier);
+  }
 }
 
 void FileSystemQuotaClient::GetStorageKeysForHost(
@@ -147,12 +215,22 @@ void FileSystemQuotaClient::GetStorageKeysForHost(
   DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
   DCHECK(!callback.is_null());
 
-  file_task_runner()->PostTaskAndReplyWithResult(
-      FROM_HERE,
-      base::BindOnce(&GetStorageKeysForHostOnFileTaskRunner,
-                     base::RetainedRef(file_system_context_), storage_type,
-                     host),
-      std::move(callback));
+  base::span<const FileSystemType> types =
+      QuotaStorageTypeToFileSystemTypes(storage_type);
+
+  base::RepeatingCallback<void(std::vector<blink::StorageKey>)> barrier =
+      base::BarrierCallback<std::vector<blink::StorageKey>>(
+          types.size(),
+          base::BindOnce(&MergeWithoutDuplicates<blink::StorageKey>)
+              .Then(std::move(callback)));
+
+  for (auto type : types) {
+    file_task_runner()->PostTaskAndReplyWithResult(
+        FROM_HERE,
+        base::BindOnce(&GetStorageKeysForHostOnFileTaskRunner,
+                       base::RetainedRef(file_system_context_), type, host),
+        barrier);
+  }
 }
 
 void FileSystemQuotaClient::DeleteStorageKeyData(
@@ -162,15 +240,29 @@ void FileSystemQuotaClient::DeleteStorageKeyData(
   DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
   DCHECK(!callback.is_null());
 
-  FileSystemType fs_type = QuotaStorageTypeToFileSystemType(type);
-  DCHECK(fs_type != kFileSystemTypeUnknown);
+  base::span<const FileSystemType> fs_types =
+      QuotaStorageTypeToFileSystemTypes(type);
 
-  file_task_runner()->PostTaskAndReplyWithResult(
-      FROM_HERE,
-      base::BindOnce(&DeleteStorageKeyOnFileTaskRunner,
-                     base::RetainedRef(file_system_context_), storage_key,
-                     fs_type),
-      std::move(callback));
+  base::RepeatingCallback<void(blink::mojom::QuotaStatusCode)> barrier =
+      base::BarrierCallback<blink::mojom::QuotaStatusCode>(
+          fs_types.size(),
+          base::BindOnce([](const std::vector<blink::mojom::QuotaStatusCode>&
+                                statuses) {
+            for (auto status : statuses) {
+              if (status != blink::mojom::QuotaStatusCode::kOk)
+                return status;
+            }
+            return blink::mojom::QuotaStatusCode::kOk;
+          }).Then(std::move(callback)));
+
+  for (const auto fs_type : fs_types) {
+    file_task_runner()->PostTaskAndReplyWithResult(
+        FROM_HERE,
+        base::BindOnce(&DeleteStorageKeyOnFileTaskRunner,
+                       base::RetainedRef(file_system_context_), storage_key,
+                       fs_type),
+        barrier);
+  }
 }
 
 void FileSystemQuotaClient::PerformStorageCleanup(
@@ -179,30 +271,19 @@ void FileSystemQuotaClient::PerformStorageCleanup(
   DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
   DCHECK(!callback.is_null());
 
-  FileSystemType fs_type = QuotaStorageTypeToFileSystemType(type);
-  DCHECK(fs_type != kFileSystemTypeUnknown);
-  file_task_runner()->PostTaskAndReply(
-      FROM_HERE,
-      base::BindOnce(&PerformStorageCleanupOnFileTaskRunner,
-                     base::RetainedRef(file_system_context_), fs_type),
-      std::move(callback));
-}
+  base::span<const FileSystemType> fs_types =
+      QuotaStorageTypeToFileSystemTypes(type);
 
-// static
-FileSystemType FileSystemQuotaClient::QuotaStorageTypeToFileSystemType(
-    blink::mojom::StorageType storage_type) {
-  switch (storage_type) {
-    case blink::mojom::StorageType::kTemporary:
-      return kFileSystemTypeTemporary;
-    case blink::mojom::StorageType::kPersistent:
-      return kFileSystemTypePersistent;
-    case blink::mojom::StorageType::kSyncable:
-      return kFileSystemTypeSyncable;
-    case blink::mojom::StorageType::kQuotaNotManaged:
-    case blink::mojom::StorageType::kUnknown:
-      return kFileSystemTypeUnknown;
+  base::RepeatingClosure barrier =
+      base::BarrierClosure(fs_types.size(), std::move(callback));
+
+  for (auto fs_type : fs_types) {
+    file_task_runner()->PostTaskAndReply(
+        FROM_HERE,
+        base::BindOnce(&PerformStorageCleanupOnFileTaskRunner,
+                       base::RetainedRef(file_system_context_), fs_type),
+        barrier);
   }
-  return kFileSystemTypeUnknown;
 }
 
 base::SequencedTaskRunner* FileSystemQuotaClient::file_task_runner() const {
diff --git a/storage/browser/file_system/file_system_quota_client.h b/storage/browser/file_system/file_system_quota_client.h
index fee07e696b2406..f686c0ee10e123 100644
--- a/storage/browser/file_system/file_system_quota_client.h
+++ b/storage/browser/file_system/file_system_quota_client.h
@@ -55,14 +55,6 @@ class COMPONENT_EXPORT(STORAGE_BROWSER) FileSystemQuotaClient
   void PerformStorageCleanup(blink::mojom::StorageType type,
                              PerformStorageCleanupCallback callback) override;
 
-  // Converts FileSystemType `type` to/from the StorageType `storage_type` that
-  // is used for the unified quota system.
-  // (Basically this naively maps TEMPORARY storage type to TEMPORARY filesystem
-  // type, PERSISTENT storage type to PERSISTENT filesystem type and vice
-  // versa.)
-  static FileSystemType QuotaStorageTypeToFileSystemType(
-      blink::mojom::StorageType storage_type);
-
  private:
   base::SequencedTaskRunner* file_task_runner() const;
 
diff --git a/storage/browser/file_system/file_system_quota_client_unittest.cc b/storage/browser/file_system/file_system_quota_client_unittest.cc
index cb8bdfd5088b74..e5c2086ce43730 100644
--- a/storage/browser/file_system/file_system_quota_client_unittest.cc
+++ b/storage/browser/file_system/file_system_quota_client_unittest.cc
@@ -13,6 +13,7 @@
 #include "base/files/scoped_temp_dir.h"
 #include "base/macros.h"
 #include "base/run_loop.h"
+#include "base/test/scoped_feature_list.h"
 #include "base/test/task_environment.h"
 #include "components/services/storage/public/mojom/quota_client.mojom.h"
 #include "storage/browser/file_system/file_system_context.h"
@@ -27,6 +28,7 @@
 #include "storage/common/file_system/file_system_util.h"
 #include "testing/gmock/include/gmock/gmock-matchers.h"
 #include "testing/gtest/include/gtest/gtest.h"
+#include "third_party/blink/public/common/features.h"
 #include "third_party/blink/public/common/storage_key/storage_key.h"
 #include "third_party/blink/public/mojom/quota/quota_types.mojom.h"
 #include "url/gurl.h"
@@ -48,17 +50,26 @@ const StorageType kPersistent = StorageType::kPersistent;
 
 }  // namespace
 
-class FileSystemQuotaClientTest : public testing::Test {
+class FileSystemQuotaClientTest : public testing::TestWithParam<bool> {
  public:
   FileSystemQuotaClientTest() = default;
   ~FileSystemQuotaClientTest() override = default;
 
   void SetUp() override {
+    if (persistent_quota_is_temporary_quota()) {
+      feature_list_.InitAndEnableFeature(
+          blink::features::kPersistentQuotaIsTemporaryQuota);
+    } else {
+      feature_list_.InitAndDisableFeature(
+          blink::features::kPersistentQuotaIsTemporaryQuota);
+    }
     ASSERT_TRUE(data_dir_.CreateUniqueTempDir());
     file_system_context_ = CreateFileSystemContextForTesting(
         /*quota_manager_proxy=*/nullptr, data_dir_.GetPath());
   }
 
+  bool persistent_quota_is_temporary_quota() const { return GetParam(); }
+
   struct TestFile {
     bool isDirectory;
     const char* name;
@@ -169,9 +180,8 @@ class FileSystemQuotaClientTest : public testing::Test {
           // create it later, this will fail due to a quota mismatch.  If we
           // call this before we create the root, it succeeds, but hasn't
           // actually created the cache.
-          ASSERT_EQ(0, GetStorageKeyUsage(
-                           quota_client, file.origin_url,
-                           FileSystemTypeToQuotaStorageType(file.type)));
+          GetStorageKeyUsage(quota_client, file.origin_url,
+                             FileSystemTypeToQuotaStorageType(file.type));
         }
       } else {
         ASSERT_TRUE(
@@ -232,6 +242,7 @@ class FileSystemQuotaClientTest : public testing::Test {
     deletion_status_ = status;
   }
 
+  base::test::ScopedFeatureList feature_list_;
   base::ScopedTempDir data_dir_;
   base::test::TaskEnvironment task_environment_;
   scoped_refptr<FileSystemContext> file_system_context_;
@@ -243,13 +254,13 @@ class FileSystemQuotaClientTest : public testing::Test {
   base::WeakPtrFactory<FileSystemQuotaClientTest> weak_factory_{this};
 };
 
-TEST_F(FileSystemQuotaClientTest, NoFileSystemTest) {
+TEST_P(FileSystemQuotaClientTest, NoFileSystemTest) {
   FileSystemQuotaClient quota_client(GetFileSystemContext());
 
   EXPECT_EQ(0, GetStorageKeyUsage(quota_client, kDummyURL1, kTemporary));
 }
 
-TEST_F(FileSystemQuotaClientTest, NoFileTest) {
+TEST_P(FileSystemQuotaClientTest, NoFileTest) {
   FileSystemQuotaClient quota_client(GetFileSystemContext());
 
   InitializeOriginFiles(quota_client,
@@ -260,7 +271,7 @@ TEST_F(FileSystemQuotaClientTest, NoFileTest) {
   }
 }
 
-TEST_F(FileSystemQuotaClientTest, OneFileTest) {
+TEST_P(FileSystemQuotaClientTest, OneFileTest) {
   FileSystemQuotaClient quota_client(GetFileSystemContext());
   const std::vector<TestFile> kFiles = {
       {true, "", 0, kDummyURL1, kFileSystemTypeTemporary},
@@ -276,7 +287,7 @@ TEST_F(FileSystemQuotaClientTest, OneFileTest) {
   }
 }
 
-TEST_F(FileSystemQuotaClientTest, TwoFilesTest) {
+TEST_P(FileSystemQuotaClientTest, TwoFilesTest) {
   FileSystemQuotaClient quota_client(GetFileSystemContext());
   const std::vector<TestFile> kFiles = {
       {true, "", 0, kDummyURL1, kFileSystemTypeTemporary},
@@ -293,7 +304,7 @@ TEST_F(FileSystemQuotaClientTest, TwoFilesTest) {
   }
 }
 
-TEST_F(FileSystemQuotaClientTest, EmptyFilesTest) {
+TEST_P(FileSystemQuotaClientTest, EmptyFilesTest) {
   FileSystemQuotaClient quota_client(GetFileSystemContext());
   const std::vector<TestFile> kFiles = {
       {true, "", 0, kDummyURL1, kFileSystemTypeTemporary},
@@ -311,7 +322,7 @@ TEST_F(FileSystemQuotaClientTest, EmptyFilesTest) {
   }
 }
 
-TEST_F(FileSystemQuotaClientTest, SubDirectoryTest) {
+TEST_P(FileSystemQuotaClientTest, SubDirectoryTest) {
   FileSystemQuotaClient quota_client(GetFileSystemContext());
   const std::vector<TestFile> kFiles = {
       {true, "", 0, kDummyURL1, kFileSystemTypeTemporary},
@@ -329,7 +340,7 @@ TEST_F(FileSystemQuotaClientTest, SubDirectoryTest) {
   }
 }
 
-TEST_F(FileSystemQuotaClientTest, MultiTypeTest) {
+TEST_P(FileSystemQuotaClientTest, MultiTypeTest) {
   FileSystemQuotaClient quota_client(GetFileSystemContext());
   const std::vector<TestFile> kFiles = {
       {true, "", 0, kDummyURL1, kFileSystemTypeTemporary},
@@ -350,14 +361,20 @@ TEST_F(FileSystemQuotaClientTest, MultiTypeTest) {
                                            kFileSystemTypePersistent);
 
   for (int i = 0; i < 2; i++) {
-    EXPECT_EQ(133 + 14 + file_paths_cost_temporary,
-              GetStorageKeyUsage(quota_client, kDummyURL1, kTemporary));
-    EXPECT_EQ(193 + 9 + file_paths_cost_persistent,
-              GetStorageKeyUsage(quota_client, kDummyURL1, kPersistent));
+    if (persistent_quota_is_temporary_quota()) {
+      EXPECT_EQ(133 + 14 + file_paths_cost_temporary + 193 + 9 +
+                    file_paths_cost_persistent,
+                GetStorageKeyUsage(quota_client, kDummyURL1, kTemporary));
+    } else {
+      EXPECT_EQ(133 + 14 + file_paths_cost_temporary,
+                GetStorageKeyUsage(quota_client, kDummyURL1, kTemporary));
+      EXPECT_EQ(193 + 9 + file_paths_cost_persistent,
+                GetStorageKeyUsage(quota_client, kDummyURL1, kPersistent));
+    }
   }
 }
 
-TEST_F(FileSystemQuotaClientTest, MultiDomainTest) {
+TEST_P(FileSystemQuotaClientTest, MultiDomainTest) {
   FileSystemQuotaClient quota_client(GetFileSystemContext());
   const std::vector<TestFile> kFiles = {
       {true, "", 0, kDummyURL1, kFileSystemTypeTemporary},
@@ -392,18 +409,27 @@ TEST_F(FileSystemQuotaClientTest, MultiDomainTest) {
                                            kFileSystemTypePersistent);
 
   for (int i = 0; i < 2; i++) {
-    EXPECT_EQ(1331 + 134 + file_paths_cost_temporary1,
-              GetStorageKeyUsage(quota_client, kDummyURL1, kTemporary));
-    EXPECT_EQ(1903 + 19 + file_paths_cost_persistent1,
-              GetStorageKeyUsage(quota_client, kDummyURL1, kPersistent));
-    EXPECT_EQ(1319 + 113 + file_paths_cost_temporary2,
-              GetStorageKeyUsage(quota_client, kDummyURL2, kTemporary));
-    EXPECT_EQ(2013 + 18 + file_paths_cost_persistent2,
-              GetStorageKeyUsage(quota_client, kDummyURL2, kPersistent));
+    if (persistent_quota_is_temporary_quota()) {
+      EXPECT_EQ(1331 + 134 + file_paths_cost_temporary1 + 1903 + 19 +
+                    file_paths_cost_persistent1,
+                GetStorageKeyUsage(quota_client, kDummyURL1, kTemporary));
+      EXPECT_EQ(1319 + 113 + file_paths_cost_temporary2 + 2013 + 18 +
+                    file_paths_cost_persistent2,
+                GetStorageKeyUsage(quota_client, kDummyURL2, kTemporary));
+    } else {
+      EXPECT_EQ(1331 + 134 + file_paths_cost_temporary1,
+                GetStorageKeyUsage(quota_client, kDummyURL1, kTemporary));
+      EXPECT_EQ(1903 + 19 + file_paths_cost_persistent1,
+                GetStorageKeyUsage(quota_client, kDummyURL1, kPersistent));
+      EXPECT_EQ(1319 + 113 + file_paths_cost_temporary2,
+                GetStorageKeyUsage(quota_client, kDummyURL2, kTemporary));
+      EXPECT_EQ(2013 + 18 + file_paths_cost_persistent2,
+                GetStorageKeyUsage(quota_client, kDummyURL2, kPersistent));
+    }
   }
 }
 
-TEST_F(FileSystemQuotaClientTest, GetUsage_MultipleTasks) {
+TEST_P(FileSystemQuotaClientTest, GetUsage_MultipleTasks) {
   FileSystemQuotaClient quota_client(GetFileSystemContext());
   const std::vector<TestFile> kFiles = {
       {true, "", 0, kDummyURL1, kFileSystemTypeTemporary},
@@ -433,7 +459,7 @@ TEST_F(FileSystemQuotaClientTest, GetUsage_MultipleTasks) {
   EXPECT_EQ(2, additional_callback_count());
 }
 
-TEST_F(FileSystemQuotaClientTest, GetStorageKeysForType) {
+TEST_P(FileSystemQuotaClientTest, GetStorageKeysForType) {
   FileSystemQuotaClient quota_client(GetFileSystemContext());
   InitializeOriginFiles(
       quota_client, {
@@ -442,13 +468,21 @@ TEST_F(FileSystemQuotaClientTest, GetStorageKeysForType) {
                         {true, "", 0, kDummyURL3, kFileSystemTypePersistent},
                     });
 
-  EXPECT_THAT(GetStorageKeysForType(quota_client, kTemporary),
-              testing::UnorderedElementsAre(
-                  StorageKey::CreateFromStringForTesting(kDummyURL1),
-                  StorageKey::CreateFromStringForTesting(kDummyURL2)));
+  if (persistent_quota_is_temporary_quota()) {
+    EXPECT_THAT(GetStorageKeysForType(quota_client, kTemporary),
+                testing::UnorderedElementsAre(
+                    StorageKey::CreateFromStringForTesting(kDummyURL1),
+                    StorageKey::CreateFromStringForTesting(kDummyURL2),
+                    StorageKey::CreateFromStringForTesting(kDummyURL3)));
+  } else {
+    EXPECT_THAT(GetStorageKeysForType(quota_client, kTemporary),
+                testing::UnorderedElementsAre(
+                    StorageKey::CreateFromStringForTesting(kDummyURL1),
+                    StorageKey::CreateFromStringForTesting(kDummyURL2)));
+  }
 }
 
-TEST_F(FileSystemQuotaClientTest, GetStorageKeysForHost) {
+TEST_P(FileSystemQuotaClientTest, GetStorageKeysForHost) {
   FileSystemQuotaClient quota_client(GetFileSystemContext());
   const char* kURL1 = "http://foo.com/";
   const char* kURL2 = "https://foo.com/";
@@ -464,14 +498,23 @@ TEST_F(FileSystemQuotaClientTest, GetStorageKeysForHost) {
                             {true, "", 0, kURL5, kFileSystemTypePersistent},
                         });
 
-  EXPECT_THAT(GetStorageKeysForHost(quota_client, kTemporary, "foo.com"),
-              testing::UnorderedElementsAre(
-                  StorageKey::CreateFromStringForTesting(kURL1),
-                  StorageKey::CreateFromStringForTesting(kURL2),
-                  StorageKey::CreateFromStringForTesting(kURL3)));
+  if (persistent_quota_is_temporary_quota()) {
+    EXPECT_THAT(GetStorageKeysForHost(quota_client, kTemporary, "foo.com"),
+                testing::UnorderedElementsAre(
+                    StorageKey::CreateFromStringForTesting(kURL1),
+                    StorageKey::CreateFromStringForTesting(kURL2),
+                    StorageKey::CreateFromStringForTesting(kURL3),
+                    StorageKey::CreateFromStringForTesting(kURL5)));
+  } else {
+    EXPECT_THAT(GetStorageKeysForHost(quota_client, kTemporary, "foo.com"),
+                testing::UnorderedElementsAre(
+                    StorageKey::CreateFromStringForTesting(kURL1),
+                    StorageKey::CreateFromStringForTesting(kURL2),
+                    StorageKey::CreateFromStringForTesting(kURL3)));
+  }
 }
 
-TEST_F(FileSystemQuotaClientTest, DeleteOriginTest) {
+TEST_P(FileSystemQuotaClientTest, DeleteOriginTest) {
   FileSystemQuotaClient quota_client(GetFileSystemContext());
   const std::vector<TestFile> kFiles = {
       {true, "", 0, "http://foo.com/", kFileSystemTypeTemporary},
@@ -499,6 +542,9 @@ TEST_F(FileSystemQuotaClientTest, DeleteOriginTest) {
   const int64_t file_paths_cost_temporary_bar =
       ComputeFilePathsCostForOriginAndType(kFiles, "http://bar.com/",
                                            kFileSystemTypeTemporary);
+  const int64_t file_paths_cost_persistent_bar =
+      ComputeFilePathsCostForOriginAndType(kFiles, "http://bar.com/",
+                                           kFileSystemTypePersistent);
   const int64_t file_paths_cost_temporary_bar_https =
       ComputeFilePathsCostForOriginAndType(kFiles, "https://bar.com/",
                                            kFileSystemTypeTemporary);
@@ -510,29 +556,44 @@ TEST_F(FileSystemQuotaClientTest, DeleteOriginTest) {
   base::RunLoop().RunUntilIdle();
   EXPECT_EQ(blink::mojom::QuotaStatusCode::kOk, status());
 
-  DeleteStorageKeyData(&quota_client, "http://bar.com/", kPersistent);
-  base::RunLoop().RunUntilIdle();
-  EXPECT_EQ(blink::mojom::QuotaStatusCode::kOk, status());
+  if (!persistent_quota_is_temporary_quota()) {
+    DeleteStorageKeyData(&quota_client, "http://bar.com/", kPersistent);
+    base::RunLoop().RunUntilIdle();
+    EXPECT_EQ(blink::mojom::QuotaStatusCode::kOk, status());
+  }
 
   DeleteStorageKeyData(&quota_client, "http://buz.com/", kTemporary);
   base::RunLoop().RunUntilIdle();
   EXPECT_EQ(blink::mojom::QuotaStatusCode::kOk, status());
 
   EXPECT_EQ(0, GetStorageKeyUsage(quota_client, "http://foo.com/", kTemporary));
-  EXPECT_EQ(0,
-            GetStorageKeyUsage(quota_client, "http://bar.com/", kPersistent));
   EXPECT_EQ(0, GetStorageKeyUsage(quota_client, "http://buz.com/", kTemporary));
-
   EXPECT_EQ(2 + file_paths_cost_temporary_foo_https,
             GetStorageKeyUsage(quota_client, "https://foo.com/", kTemporary));
-  EXPECT_EQ(4 + file_paths_cost_persistent_foo,
-            GetStorageKeyUsage(quota_client, "http://foo.com/", kPersistent));
-  EXPECT_EQ(8 + file_paths_cost_temporary_bar,
+  EXPECT_EQ(8 + file_paths_cost_temporary_bar +
+                (persistent_quota_is_temporary_quota()
+                     ? 16 + file_paths_cost_persistent_bar
+                     : 0),
             GetStorageKeyUsage(quota_client, "http://bar.com/", kTemporary));
-  EXPECT_EQ(32 + file_paths_cost_persistent_bar_https,
-            GetStorageKeyUsage(quota_client, "https://bar.com/", kPersistent));
-  EXPECT_EQ(64 + file_paths_cost_temporary_bar_https,
+  EXPECT_EQ(64 + file_paths_cost_temporary_bar_https +
+                (persistent_quota_is_temporary_quota()
+                     ? 32 + file_paths_cost_persistent_bar_https
+                     : 0),
             GetStorageKeyUsage(quota_client, "https://bar.com/", kTemporary));
+
+  if (!persistent_quota_is_temporary_quota()) {
+    EXPECT_EQ(0,
+              GetStorageKeyUsage(quota_client, "http://bar.com/", kPersistent));
+    EXPECT_EQ(4 + file_paths_cost_persistent_foo,
+              GetStorageKeyUsage(quota_client, "http://foo.com/", kPersistent));
+    EXPECT_EQ(
+        32 + file_paths_cost_persistent_bar_https,
+        GetStorageKeyUsage(quota_client, "https://bar.com/", kPersistent));
+  }
 }
 
+INSTANTIATE_TEST_SUITE_P(FileSystemQuotaClientTests,
+                         FileSystemQuotaClientTest,
+                         testing::Bool());
+
 }  // namespace storage
diff --git a/storage/browser/file_system/file_system_util.cc b/storage/browser/file_system/file_system_util.cc
index 95b190f68b323c..a32a53f267682a 100644
--- a/storage/browser/file_system/file_system_util.cc
+++ b/storage/browser/file_system/file_system_util.cc
@@ -4,13 +4,20 @@
 
 #include "storage/browser/file_system/file_system_util.h"
 
+#include "base/feature_list.h"
 #include "storage/common/file_system/file_system_types.h"
+#include "third_party/blink/public/common/features.h"
 #include "third_party/blink/public/mojom/quota/quota_types.mojom.h"
 
 namespace storage {
 
 blink::mojom::StorageType FileSystemTypeToQuotaStorageType(
     FileSystemType type) {
+  if (base::FeatureList::IsEnabled(
+          blink::features::kPersistentQuotaIsTemporaryQuota) &&
+      (type == kFileSystemTypeTemporary || type == kFileSystemTypePersistent)) {
+    return blink::mojom::StorageType::kTemporary;
+  }
   switch (type) {
     case kFileSystemTypeTemporary:
       return blink::mojom::StorageType::kTemporary;
diff --git a/storage/browser/quota/quota_features.cc b/storage/browser/quota/quota_features.cc
index cfb874fbd0f7be..04985ab9fc0a70 100644
--- a/storage/browser/quota/quota_features.cc
+++ b/storage/browser/quota/quota_features.cc
@@ -3,6 +3,7 @@
 // found in the LICENSE file.
 
 #include "storage/browser/quota/quota_features.h"
+#include "base/feature_list.h"
 
 namespace storage {
 
diff --git a/third_party/blink/common/features.cc b/third_party/blink/common/features.cc
index 7878b143acc232..45905c38073246 100644
--- a/third_party/blink/common/features.cc
+++ b/third_party/blink/common/features.cc
@@ -1028,5 +1028,8 @@ const base::Feature kDeprecateThirdPartyContextWebSQL{
 const base::Feature kSyncLoadDataUrlFonts{"SyncLoadDataUrlFonts",
                                           base::FEATURE_DISABLED_BY_DEFAULT};
 
+const base::Feature kPersistentQuotaIsTemporaryQuota{
+    "PersistentQuotaIsTemporaryQuota", base::FEATURE_DISABLED_BY_DEFAULT};
+
 }  // namespace features
 }  // namespace blink
diff --git a/third_party/blink/public/common/features.h b/third_party/blink/public/common/features.h
index c332d6aaf7fa5a..0bb61b65cbf77d 100644
--- a/third_party/blink/public/common/features.h
+++ b/third_party/blink/public/common/features.h
@@ -446,6 +446,10 @@ BLINK_COMMON_EXPORT extern const base::Feature
 // Synchronously load web fonts inlined as data urls. See crbug.com/1236283
 BLINK_COMMON_EXPORT extern const base::Feature kSyncLoadDataUrlFonts;
 
+// Makes Persistent quota the same as Temporary quota.
+BLINK_COMMON_EXPORT
+extern const base::Feature kPersistentQuotaIsTemporaryQuota;
+
 }  // namespace features
 }  // namespace blink
 
diff --git a/tools/metrics/histograms/enums.xml b/tools/metrics/histograms/enums.xml
index ff289d337d6517..d31712b87241c8 100644
--- a/tools/metrics/histograms/enums.xml
+++ b/tools/metrics/histograms/enums.xml
@@ -49116,6 +49116,7 @@ from previous Chrome versions.
   <int value="-270261701" label="WebRtcEnableCaptureMultiChannelApm:disabled"/>
   <int value="-269440655"
       label="AutofillDownstreamCvcPromptUseGooglePayLogo:disabled"/>
+  <int value="-269227049" label="PersistentQuotaIsTemporaryQuota:enabled"/>
   <int value="-268897347" label="DisableCameraFrameRotationAtSource:disabled"/>
   <int value="-268549184"
       label="AutofillSaveCreditCardUsesStrikeSystemV2:enabled"/>
@@ -49726,6 +49727,7 @@ from previous Chrome versions.
   <int value="246106068" label="HandwritingLegacyRecognition:disabled"/>
   <int value="247200195" label="EnhancedProtectionPromoCard:enabled"/>
   <int value="250855010" label="WebAssemblyBaseline:disabled"/>
+  <int value="251367892" label="PersistentQuotaIsTemporaryQuota:disabled"/>
   <int value="254497185" label="VideoPlayerJsModules:enabled"/>
   <int value="255375615" label="stop-non-timers-in-background:enabled"/>
   <int value="258621334"