dio_web_adapter

If you encounter bugs, consider fixing it by opening a PR or at least contribute a failing test case.

This package contains adapters for Dio which enables you to use the library on the Web platform.

Versions compatibility

Note: the resolvable version will be determined by the SDK you are using. Run dart pub upgrade or flutter pub upgrade to get the latest resolvable version.

Get started

The package is embedded into the package:dio. You don't need to explicitly install the package unless you have other concerns.

Install

Add the dio_web_adapter package to your pubspec dependencies.

Example

import 'package:dio/dio.dart';
// The import is not required and could produce lints.
// import 'package:dio_web_adapter/dio_web_adapter.dart';

void main() async {
  final dio = Dio();
  dio.httpClientAdapter = BrowserHttpClientAdapter(withCredentials: true);

  // Make a request.
  final response = await dio.get('https://dart.dev');
  print(response);
}

Downloading files

Dio.download is supported on Web by fetching the response bytes and triggering a browser download with a Blob URL. The savePath argument is treated as the suggested filename, not as a local filesystem path. The browser decides the actual save location.

The browser schedules the download from a blob: URL created in the current page. A returned Response means Dio fetched the response and dispatched the browser download click; it does not guarantee that the browser wrote the file to disk, kept the suggested filename, or skipped a user prompt. Those decisions are controlled by the browser, user settings, and page security policies.

Web downloads have platform limitations:

• The request is still subject to CORS because it is fetched through Dio.
• The network request is handled by the browser through XHR, so HTTP protocol details such as HTTP/1.1, HTTP/2, or HTTP/3 are browser-controlled.
• The whole response is loaded into memory before the browser download starts.
• The download trigger relies on standard browser support for Blob, URL.createObjectURL, and HTMLAnchorElement.download.
• FileAccessMode.append is not supported.
• deleteOnError has no local file to delete on Web.
• Custom lengthHeader values are not used; progress totals come from the browser response progress event.