diff --git a/packages/webview_flutter/webview_flutter_web/CHANGELOG.md b/packages/webview_flutter/webview_flutter_web/CHANGELOG.md
index 8ab70f9a78d3..631608689a7a 100644
--- a/packages/webview_flutter/webview_flutter_web/CHANGELOG.md
+++ b/packages/webview_flutter/webview_flutter_web/CHANGELOG.md
@@ -1,3 +1,7 @@
+## 0.1.0+4
+
+* Fixes incorrect escaping of some characters when setting the HTML to the iframe element.
+
 ## 0.1.0+3
 
 * Minor fixes for new analysis options.
diff --git a/packages/webview_flutter/webview_flutter_web/lib/webview_flutter_web.dart b/packages/webview_flutter/webview_flutter_web/lib/webview_flutter_web.dart
index 637c24926275..adf6495b8f2a 100644
--- a/packages/webview_flutter/webview_flutter_web/lib/webview_flutter_web.dart
+++ b/packages/webview_flutter/webview_flutter_web/lib/webview_flutter_web.dart
@@ -3,6 +3,7 @@
 // found in the LICENSE file.
 
 import 'dart:async';
+import 'dart:convert';
 import 'dart:html';
 import 'package:flutter/foundation.dart';
 import 'package:flutter/gestures.dart';
@@ -183,7 +184,11 @@ class WebWebViewPlatformController implements WebViewPlatformController {
     String? baseUrl,
   }) async {
     // ignore: unsafe_html
-    _element.src = 'data:text/html,${Uri.encodeFull(html)}';
+    _element.src = Uri.dataFromString(
+      html,
+      mimeType: 'text/html',
+      encoding: utf8,
+    ).toString();
   }
 
   @override
@@ -199,8 +204,11 @@ class WebWebViewPlatformController implements WebViewPlatformController {
     final String contentType =
         httpReq.getResponseHeader('content-type') ?? 'text/html';
     // ignore: unsafe_html
-    _element.src =
-        'data:$contentType,${Uri.encodeFull(httpReq.responseText ?? '')}';
+    _element.src = Uri.dataFromString(
+      httpReq.responseText ?? '',
+      mimeType: contentType,
+      encoding: utf8,
+    ).toString();
   }
 
   @override
diff --git a/packages/webview_flutter/webview_flutter_web/pubspec.yaml b/packages/webview_flutter/webview_flutter_web/pubspec.yaml
index 6464e20fe37c..12bec7242519 100644
--- a/packages/webview_flutter/webview_flutter_web/pubspec.yaml
+++ b/packages/webview_flutter/webview_flutter_web/pubspec.yaml
@@ -2,7 +2,7 @@ name: webview_flutter_web
 description: A Flutter plugin that provides a WebView widget on web.
 repository: https://github.com/flutter/plugins/tree/main/packages/webview_flutter/webview_flutter_web
 issue_tracker: https://github.com/flutter/flutter/issues?q=is%3Aissue+is%3Aopen+label%3A%22p%3A+webview%22
-version: 0.1.0+3
+version: 0.1.0+4
 
 environment:
   sdk: ">=2.14.0 <3.0.0"
diff --git a/packages/webview_flutter/webview_flutter_web/test/webview_flutter_web_test.dart b/packages/webview_flutter/webview_flutter_web/test/webview_flutter_web_test.dart
index 6058dcf07272..08337e42e661 100644
--- a/packages/webview_flutter/webview_flutter_web/test/webview_flutter_web_test.dart
+++ b/packages/webview_flutter/webview_flutter_web/test/webview_flutter_web_test.dart
@@ -54,17 +54,33 @@ void main() {
       verify(mockElement.src = 'test url');
     });
 
-    test('loadHtmlString loads html into iframe', () {
-      // Setup
-      final MockIFrameElement mockElement = MockIFrameElement();
-      final WebWebViewPlatformController controller =
-          WebWebViewPlatformController(
-        mockElement,
-      );
-      // Run
-      controller.loadHtmlString('test html');
-      // Verify
-      verify(mockElement.src = 'data:text/html,${Uri.encodeFull('test html')}');
+    group('loadHtmlString', () {
+      test('loadHtmlString loads html into iframe', () {
+        // Setup
+        final MockIFrameElement mockElement = MockIFrameElement();
+        final WebWebViewPlatformController controller =
+            WebWebViewPlatformController(
+          mockElement,
+        );
+        // Run
+        controller.loadHtmlString('test html');
+        // Verify
+        verify(mockElement.src =
+            'data:text/html;charset=utf-8,${Uri.encodeFull('test html')}');
+      });
+
+      test('loadHtmlString escapes "#" correctly', () {
+        // Setup
+        final MockIFrameElement mockElement = MockIFrameElement();
+        final WebWebViewPlatformController controller =
+            WebWebViewPlatformController(
+          mockElement,
+        );
+        // Run
+        controller.loadHtmlString('#');
+        // Verify
+        verify(mockElement.src = argThat(contains('%23')));
+      });
     });
 
     group('loadRequest', () {
@@ -122,8 +138,40 @@ void main() {
           requestHeaders: <String, String>{'Foo': 'Bar'},
           sendData: Uint8List.fromList('test body'.codeUnits),
         ));
-        verify(
-            mockElement.src = 'data:text/plain,${Uri.encodeFull('test data')}');
+        verify(mockElement.src =
+            'data:;charset=utf-8,${Uri.encodeFull('test data')}');
+      });
+
+      test('loadRequest escapes "#" correctly', () async {
+        // Setup
+        final MockIFrameElement mockElement = MockIFrameElement();
+        final WebWebViewPlatformController controller =
+            WebWebViewPlatformController(
+          mockElement,
+        );
+        final MockHttpRequest mockHttpRequest = MockHttpRequest();
+        when(mockHttpRequest.getResponseHeader('content-type'))
+            .thenReturn('text/html');
+        when(mockHttpRequest.responseText).thenReturn('#');
+        final MockHttpRequestFactory mockHttpRequestFactory =
+            MockHttpRequestFactory();
+        when(mockHttpRequestFactory.request(
+          any,
+          method: anyNamed('method'),
+          requestHeaders: anyNamed('requestHeaders'),
+          sendData: anyNamed('sendData'),
+        )).thenAnswer((_) => Future<HttpRequest>.value(mockHttpRequest));
+        controller.httpRequestFactory = mockHttpRequestFactory;
+        // Run
+        await controller.loadRequest(
+          WebViewRequest(
+              uri: Uri.parse('https://flutter.dev'),
+              method: WebViewRequestMethod.post,
+              body: Uint8List.fromList('test body'.codeUnits),
+              headers: <String, String>{'Foo': 'Bar'}),
+        );
+        // Verify
+        verify(mockElement.src = argThat(contains('%23')));
       });
     });
   });