diff --git a/CHANGELOG.md b/CHANGELOG.md
index 2864af8..c59286d 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,12 @@
 # CHANGELOG
 
+## NEXT
+
+- `CookieJar` now returns `FutureOr` instead of `Future` for all methods.
+- Deprecates `delete` in favor of `deleteWhere`.
+- Adds `loadAll` to get all saved Cookies.
+- Adds `endSession` to delete all session Cookies.
+
 ## 4.0.8
 
 - Simply replace `\` to `/` rather than using `Uri` when parsing a storage base directory.
diff --git a/example/encryption.dart b/example/encryption.dart
index 4be8a5f..530e205 100644
--- a/example/encryption.dart
+++ b/example/encryption.dart
@@ -17,7 +17,7 @@ void main() async {
   final cj = PersistCookieJar(ignoreExpires: true, storage: storage);
 
   final uri = Uri.parse('https://xxx.xxx.com/');
-  await cj.delete(uri);
+  await cj.deleteWhere((cookie) => cookie.domain == uri.host);
   List<Cookie> results;
   final cookie = Cookie('test', 'hh')
     ..expires = DateTime.parse('1970-02-27 13:27:00');
diff --git a/lib/src/cookie_jar.dart b/lib/src/cookie_jar.dart
index 36903f3..ac5190a 100644
--- a/lib/src/cookie_jar.dart
+++ b/lib/src/cookie_jar.dart
@@ -1,3 +1,5 @@
+import 'dart:async';
+
 import 'package:universal_io/io.dart' show Cookie;
 
 import 'jar/default.dart';
@@ -7,8 +9,66 @@ const _kIsWeb = bool.hasEnvironment('dart.library.js_util')
     ? bool.fromEnvironment('dart.library.js_util')
     : identical(0, 0.0);
 
-/// [CookieJar] is a cookie container and manager for HTTP requests.
+/// [CookieJar] is a cookie container and manager for HTTP requests implementing [RFC6265](https://www.rfc-editor.org/rfc/rfc6265.html).
+///
+/// ## Implementation considerations
+/// In most cases it is not needed to implement this interface.
+/// Use a `PersistCookieJar` with a custom [Storage] backend.
+///
+/// ### Cookie value retrieval
+/// A cookie jar does not need to retrieve cookies with all attributes present.
+/// Retrieved cookies only need to have a valid [Cookie.name] and [Cookie.value].
+/// It is up to the implementation to provide further information.
+///
+/// ### Cookie management
+/// According to [RFC6265 section 7.2](https://www.rfc-editor.org/rfc/rfc6265.html#section-7.2)
+/// user agents SHOULD provide users with a mechanism for managing the cookies stored in the cookie jar.
+/// It must be documented if an implementer does not provide any of the optional
+/// [loadAll], [deleteAll] and [deleteWhere] methods.
+///
+/// ### Public suffix validation
+/// The default implementation does not validate the cookie domain against a public
+/// suffix list.
+/// {@template CookieJar.publicSuffixNote}
+/// > NOTE: A "public suffix" is a domain that is controlled by a public
+/// > registry, such as "com", "co.uk", and "pvt.k12.wy.us". This step is
+/// > essential for preventing attacker.com from disrupting the integrity of
+/// > example.com by setting a cookie with a Domain attribute of "com".
+/// > Unfortunately, the set of public suffixes (also known as "registry controlled domains")
+/// > changes over time. If feasible, user agents SHOULD use an up-to-date
+/// > public suffix list, such as the one maintained by the Mozilla project at <http://publicsuffix.org/>.
+/// {@endtemplate}
+///
+/// ### CookieJar limits and eviction policy
+/// If a cookie jar has a limit to the number of cookies it can store,
+/// the removal policy outlined in [RFC6265 section 5.3](https://www.rfc-editor.org/rfc/rfc6265.html#section-5.3)
+/// must be followed:
+/// > At any time, the user agent MAY "remove excess cookies" from the cookie store
+/// > if the number of cookies sharing a domain field exceeds some implementation-defined
+/// > upper bound (such as 50 cookies).
+/// >
+/// > At any time, the user agent MAY "remove excess cookies" from the cookie store
+/// > if the cookie store exceeds some predetermined upper bound (such as 3000 cookies).
+/// >
+/// > When the user agent removes excess cookies from the cookie store, the user agent MUST
+/// > evict cookies in the following priority order:
+/// >
+/// >    Expired cookies.
+/// >    Cookies that share a domain field with more than a predetermined number of other cookies.
+/// >    All cookies.
+/// >
+/// > If two cookies have the same removal priority, the user agent MUST evict the
+/// > cookie with the earliest last-access date first.
+///
+/// It is recommended to set an upper bound to the time a cookie is stored
+/// as described in [RFC6265 section 7.3](https://www.rfc-editor.org/rfc/rfc6265.html#section-7.3):
+/// > Although servers can set the expiration date for cookies to the distant future,
+/// > most user agents do not actually retain cookies for multiple decades.
+/// > Rather than choosing gratuitously long expiration periods, servers SHOULD
+/// > promote user privacy by selecting reasonable cookie expiration periods based on the purpose of the cookie.
+/// > For example, a typical session identifier might reasonably be set to expire in two weeks.
 abstract class CookieJar {
+  /// Creates a [DefaultCookieJar] instance or a dummy [WebCookieJar] if run in a browser.
   factory CookieJar({bool ignoreExpires = false}) {
     if (_kIsWeb) {
       return WebCookieJar();
@@ -16,18 +76,39 @@ abstract class CookieJar {
     return DefaultCookieJar(ignoreExpires: ignoreExpires);
   }
 
-  /// Whether the [CookieJar] should ignore expired cookies during saves/loads.
-  final bool ignoreExpires = false;
-
   /// Save the [cookies] for specified [uri].
-  Future<void> saveFromResponse(Uri uri, List<Cookie> cookies);
+  FutureOr<void> saveFromResponse(Uri uri, List<Cookie> cookies);
 
   /// Load the cookies for specified [uri].
-  Future<List<Cookie>> loadForRequest(Uri uri);
+  FutureOr<List<Cookie>> loadForRequest(Uri uri);
+
+  /// Ends the current session deleting all session cookies.
+  FutureOr<void> endSession();
+
+  /// Loads all cookies in the jar.
+  ///
+  /// User agents SHOULD provide users with a mechanism for managing the cookies stored in the cookie jar.
+  /// https://www.rfc-editor.org/rfc/rfc6265.html#section-7.2
+  ///
+  /// Implementing this method is optional. It must be documented if the
+  /// implementer does not support this operation.
+  FutureOr<List<Cookie>> loadAll();
 
-  /// Delete all cookies in the [CookieJar].
-  Future<void> deleteAll();
+  /// Deletes all cookies in the jar.
+  ///
+  /// User agents SHOULD provide users with a mechanism for managing the cookies stored in the cookie jar.
+  /// https://www.rfc-editor.org/rfc/rfc6265.html#section-7.2
+  ///
+  /// Implementing this method is optional. It must be documented if the
+  /// implementer does not support this operation.
+  FutureOr<void> deleteAll();
 
-  /// Delete cookies with the specified [uri].
-  Future<void> delete(Uri uri, [bool withDomainSharedCookie = false]);
+  /// Removes all cookies in this store that satisfy the given [test].
+  ///
+  /// User agents SHOULD provide users with a mechanism for managing the cookies stored in the cookie store.
+  /// https://www.rfc-editor.org/rfc/rfc6265.html#section-7.2
+  ///
+  /// Implementing this method is optional. It must be documented if the
+  /// implementer does not support this operation.
+  FutureOr<void> deleteWhere(bool Function(Cookie cookie) test);
 }
diff --git a/lib/src/jar/default.dart b/lib/src/jar/default.dart
index 4a0f936..26a4c07 100644
--- a/lib/src/jar/default.dart
+++ b/lib/src/jar/default.dart
@@ -1,3 +1,5 @@
+import 'dart:async';
+
 import 'package:universal_io/io.dart' show Cookie;
 
 import '../cookie_jar.dart';
@@ -10,10 +12,14 @@ import '../serializable_cookie.dart';
 /// cleared after the app exited.
 ///
 /// In order to save cookies into storages, use [PersistCookieJar] instead.
+///
+/// ### Public suffix validation
+/// This cookie jar implementation does not validate the cookie domain against a
+/// public suffix list.
+/// {@macro CookieJar.publicSuffixNote}
 class DefaultCookieJar implements CookieJar {
   DefaultCookieJar({this.ignoreExpires = false});
 
-  @override
   final bool ignoreExpires;
 
   /// An array to save cookies.
@@ -88,7 +94,7 @@ class DefaultCookieJar implements CookieJar {
   }
 
   @override
-  Future<List<Cookie>> loadForRequest(Uri uri) async {
+  FutureOr<List<Cookie>> loadForRequest(Uri uri) {
     final list = <Cookie>[];
     final urlPath = uri.path;
     // Load cookies without "domain" attribute, include port.
@@ -137,7 +143,7 @@ class DefaultCookieJar implements CookieJar {
   }
 
   @override
-  Future<void> saveFromResponse(Uri uri, List<Cookie> cookies) async {
+  FutureOr<void> saveFromResponse(Uri uri, List<Cookie> cookies) {
     for (final cookie in cookies) {
       String? domain = cookie.domain;
       String path;
@@ -173,8 +179,8 @@ class DefaultCookieJar implements CookieJar {
   /// This API will delete all cookies for the `uri.host`, it will ignored the `uri.path`.
   ///
   /// [withDomainSharedCookie] `true` will delete the domain-shared cookies.
-  @override
-  Future<void> delete(Uri uri, [bool withDomainSharedCookie = false]) async {
+  @Deprecated('Use deleteWhere instead')
+  FutureOr<void> delete(Uri uri, [bool withDomainSharedCookie = false]) {
     final host = uri.host;
     hostCookies.remove(host);
     if (withDomainSharedCookie) {
@@ -186,7 +192,7 @@ class DefaultCookieJar implements CookieJar {
 
   /// Delete all cookies stored in the memory.
   @override
-  Future<void> deleteAll() async {
+  FutureOr<void> deleteAll() {
     domainCookies.clear();
     hostCookies.clear();
   }
@@ -206,4 +212,40 @@ class DefaultCookieJar implements CookieJar {
     final list = path.split('/')..removeLast();
     return list.join('/');
   }
+
+  @override
+  void deleteWhere(bool Function(Cookie cookie) test) {
+    // Traverse all managed cookies and delete entries matching `test`.
+    for (final group in _cookies) {
+      for (final domainPair in group.values) {
+        for (final pathPair in domainPair.values) {
+          pathPair.removeWhere((key, value) => test(value.cookie));
+        }
+      }
+    }
+  }
+
+  @override
+  void endSession() {
+    deleteWhere((cookie) {
+      return cookie.expires == null && cookie.maxAge == null;
+    });
+  }
+
+  @override
+  FutureOr<List<Cookie>> loadAll() {
+    final list = <Cookie>[];
+
+    for (final group in _cookies) {
+      for (final domainPair in group.values) {
+        for (final pathPair in domainPair.values) {
+          for (final value in pathPair.values) {
+            list.add(value.cookie);
+          }
+        }
+      }
+    }
+
+    return list;
+  }
 }
diff --git a/lib/src/jar/persist.dart b/lib/src/jar/persist.dart
index 8c1ab13..7c07001 100644
--- a/lib/src/jar/persist.dart
+++ b/lib/src/jar/persist.dart
@@ -10,7 +10,7 @@ import 'default.dart';
 /// [PersistCookieJar] is a cookie manager which implements
 /// the standard cookie policy declared in RFC.
 /// [PersistCookieJar]  persists the cookies in files, if the application exit,
-/// the cookies always exist unless user explicitly called [delete].
+/// the cookies always exist unless user explicitly deleted with [deleteWhere].
 class PersistCookieJar extends DefaultCookieJar {
   /// [persistSession] is whether persisting the cookies that without
   /// "expires" or "max-age" attribute.
@@ -157,6 +157,7 @@ class PersistCookieJar extends DefaultCookieJar {
   /// This API will delete all cookies for the `uri.host`, it will ignored the `uri.path`.
   ///
   /// [withDomainSharedCookie] `true` will delete the domain-shared cookies.
+  @Deprecated('Use deleteWhere instead')
   @override
   Future<void> delete(Uri uri, [bool withDomainSharedCookie = false]) async {
     await _checkInitialized();
@@ -171,6 +172,15 @@ class PersistCookieJar extends DefaultCookieJar {
     }
   }
 
+  @override
+  Future<void> deleteWhere(bool Function(Cookie cookie) test) async {
+    await _checkInitialized();
+    super.deleteWhere(test);
+
+    await storage.write(_indexKey, json.encode(_hostSet.toList()));
+    await storage.write(_domainsKey, json.encode(domainCookies));
+  }
+
   /// Delete all cookies files in the [storage] and the memory.
   @override
   Future<void> deleteAll() async {
diff --git a/lib/src/jar/web.dart b/lib/src/jar/web.dart
index 50c5577..a6fc637 100644
--- a/lib/src/jar/web.dart
+++ b/lib/src/jar/web.dart
@@ -5,20 +5,23 @@ import '../cookie_jar.dart';
 /// A [WebCookieJar] will do nothing to handle cookies
 /// since they are already handled by XHRs.
 class WebCookieJar implements CookieJar {
-  WebCookieJar({this.ignoreExpires = false});
+  WebCookieJar();
 
   @override
-  final bool ignoreExpires;
+  void deleteWhere(bool Function(Cookie cookie) test) {}
 
   @override
-  Future<void> delete(Uri uri, [bool withDomainSharedCookie = false]) async {}
+  void deleteAll() {}
 
   @override
-  Future<void> deleteAll() async {}
+  List<Cookie> loadForRequest(Uri uri) => [];
 
   @override
-  Future<List<Cookie>> loadForRequest(Uri uri) async => [];
+  void saveFromResponse(Uri uri, List<Cookie> cookies) {}
 
   @override
-  Future<void> saveFromResponse(Uri uri, List<Cookie> cookies) async {}
+  void endSession() {}
+
+  @override
+  List<Cookie> loadAll() => [];
 }
diff --git a/migration_guide.md b/migration_guide.md
index 299a378..b4a3b2f 100644
--- a/migration_guide.md
+++ b/migration_guide.md
@@ -1,6 +1,6 @@
 # Migration Guide
 
-This document gathered all breaking changes and migrations requirement between versions.
+This document gathered all breaking changes and migration requirements between versions.
 
 <!--
 When new content need to be added to the migration guide, make sure they're following the format:
@@ -10,19 +10,51 @@ When new content need to be added to the migration guide, make sure they're foll
 
 ## Breaking versions
 
+# NEXT
+
+Version 5.0 brings a few refinements to the `CookieJar` interface.
+Breaking changes include:
+
+- Usage of `FutureOr` in interfaces.
+  Going forward a `CookieJar` can also return synchronously. If every call is 
+  properly awaited, nothing should break.
+  Usage in an `unawaited` method is no longer possible. The `WebCookieJar` has
+  been migrated to always complete synchronously.
+
+- Changing Cookie deletion:
+  To allow implementers further flexibility the `delete` method has been removed
+  from the `CookieJar` interface. Users should migrate to the more flexible 
+  `deleteWhere` method:
+  ```dart
+  final jar = CookieJar();
+  // Check what Cookies you want to have deleted.
+  jar.deleteWhere((cookie) {
+    return cookie.domain == 'example.com' || cookie.name == 'cookie1';
+  }));
+  ```
+
+- Optional Cookie management interface:
+  Cookie management interfaces like `deleteAll`, `deleteWhere` or `loadAll` have
+  been made optional. It is up to the implementer to support these operations.
+  Consult your implementers' documentation.
+
+- Optional extra Cookie parameters:
+  When loading Cookies in any way from the store (`loadForRequest`, `deleteWhere` or `loadAll`)
+  implementers only have to provide the `Cookie.name` and `Cookie.value` attributes.
+
 - [4.0.0](#400)
 
 # 4.0.0
 
-In version 3.0, when the path of cookie is not specified, '/' will be used.
+In version 3.0, when the path of Cookie is not specified, '/' will be used.
 However, this is not standard.
 In this case, the current URL path should be used.
 Therefore, in 4.x, we updated it, but this will cause the
 **PersistCookieJar in 4.x to be incompatible with the PersistCookieJar in 3.0**,
-that is say, we cannot continue to read and write old cookies in 4.x.
-We can upgrade to 4.x through one of following two steps:
+that is to say, we cannot continue to read and write old Cookies in 4.x.
+We can upgrade to 4.x through one of the following two steps:
 
-- Delete old cookies (Note: The following code should only be executed once):
+- Delete old Cookies (Note: The following code should only be executed once):
   ```dart
   // `ignoreExpires` and `oldPath` must be same with 3.x .
   PersistCookieJar(
@@ -30,7 +62,7 @@ We can upgrade to 4.x through one of following two steps:
     storage: FileStorage(oldPath),
   ).deleteAll();
   ```
-- Or use a new cookie file (ignore old cookies).
+- Or use a new Cookie file (ignore old Cookies).
   ```dart
   PersistCookieJar( 
     // The path should be different from that in 3.x。
diff --git a/pubspec.yaml b/pubspec.yaml
index 687a69e..6842008 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -1,11 +1,11 @@
 name: cookie_jar
 description: A cookie manager for http requests in Dart, help you to deal with the cookie policies and persistence.
-version: 4.0.8
+version: 5.0.0-dev.1
 repository: https://github.com/flutterchina/cookie_jar
 issue_tracker: https://github.com/flutterchina/cookie_jar/issues
 
 environment:
-  sdk: '>=2.15.0 <3.0.0'
+  sdk: ">=2.15.0 <4.0.0"
 
 dependencies:
   meta: ^1.5.0
diff --git a/test/cookie_jar_test.dart b/test/cookie_jar_test.dart
index 40d7bd9..771653c 100644
--- a/test/cookie_jar_test.dart
+++ b/test/cookie_jar_test.dart
@@ -165,17 +165,19 @@ void main() async {
     });
 
     test('DeleteDomainSharedCookie', () async {
-      final cj = CookieJar();
+      final cj = DefaultCookieJar();
       final cookies = <Cookie>[
         Cookie('JSESSIONID', 'wendux')..domain = '.mozilla.org',
       ];
       await cj.saveFromResponse(Uri.parse('https://www.mozilla.org/'), cookies);
 
+      // ignore: deprecated_member_use_from_same_package
       await cj.delete(Uri.parse('https://www.fakemozilla.org/'), true);
       final results1 =
           await cj.loadForRequest(Uri.parse('https://www.mozilla.org/'));
       expect(results1.length, 1);
 
+      // ignore: deprecated_member_use_from_same_package
       await cj.delete(Uri.parse('https://developer.mozilla.org/'), true);
       final results2 =
           await cj.loadForRequest(Uri.parse('https://www.mozilla.org/'));
@@ -195,6 +197,7 @@ void main() async {
       List<Cookie> results =
           await cj.loadForRequest(Uri.parse('https://tt.facebook.com/xxx'));
       expect(results.length, 1);
+      // ignore: deprecated_member_use_from_same_package
       await cj.delete(Uri.parse('https://www.facebook.com/'));
       results =
           await cj.loadForRequest(Uri.parse('https://tt.facebook.com/xxx'));
@@ -207,6 +210,7 @@ void main() async {
         storage: FileStorage('./test/cookies'),
       );
       final uri = Uri.parse('https://xxx.com/');
+      // ignore: deprecated_member_use_from_same_package
       await cj.delete(uri);
 
       List<Cookie> results;
@@ -240,6 +244,7 @@ void main() async {
       );
 
       final uri = Uri.parse('https://xxx.xxx.com/');
+      // ignore: deprecated_member_use_from_same_package
       await cj.delete(uri);
       List<Cookie> results;
       final cookie = Cookie('test', 'hh')
@@ -275,6 +280,25 @@ void main() async {
     expect(otherResults, isEmpty);
   });
 
+  test('Delete session cookies', () async {
+    final cj = CookieJar();
+    await cj.saveFromResponse(
+      Uri(host: 'example.com', path: '/'),
+      cookies,
+    );
+    await cj.saveFromResponse(
+      Uri(host: 'mozilla.org', path: '/'),
+      cookiesExpired,
+    );
+
+    var results = await cj.loadAll();
+    expect(results, hasLength(4));
+
+    await cj.endSession();
+    results = await cj.loadAll();
+    expect(results, hasLength(2));
+  });
+
   group('Test session cookies persistance', () {
     test('PersistCookieJar persists session cookies by default', () async {
       final uri = Uri.parse('https://session-default-test.com/');
diff --git a/test/web_test.dart b/test/web_test.dart
index 0b43463..223f685 100644
--- a/test/web_test.dart
+++ b/test/web_test.dart
@@ -8,7 +8,6 @@ void main() {
   test('Constructed a WebCookieJar', () async {
     final cj = CookieJar();
     expect(cj, isA<WebCookieJar>());
-    await cj.delete(Uri());
     await cj.deleteAll();
     await cj.saveFromResponse(Uri(), []);
     final cookies = await cj.loadForRequest(Uri());