A Windows HTTP client for package:http using the native WinHTTP API.

Motivation

Using WinHTTP, rather than the socket-based dart:io HttpClient implementation, has several advantages:

1. It automatically supports Windows system proxy settings (WPAD, PAC scripts).
2. It uses the Windows TLS stack (Schannel) with system certificate stores.
3. It supports automatic gzip/deflate decompression.
4. It integrates with Windows network diagnostics and logging.

Requirements

• Windows 8.1 or later (required for automatic proxy detection and decompression)
• Dart SDK 3.4+

Using

The easiest way to use this library is via the high-level interface defined by package:http Client.

This approach allows the same HTTP code to be used on all platforms, while still allowing platform-specific setup.

import 'dart:io';

import 'package:http/http.dart';
import 'package:http/io_client.dart';
import 'package:win_http/win_http.dart';

void main() async {
  final Client httpClient;
  if (Platform.isWindows) {
    httpClient = WinHttpClient.defaultConfiguration();
  } else {
    httpClient = IOClient();
  }

  final response = await httpClient.get(
    Uri.https('www.googleapis.com', '/books/v1/volumes', {'q': 'dart'}),
  );
  print('Status: ${response.statusCode}');
  httpClient.close();
}

Configuration

Use WinHttpClient.fromConfiguration for custom settings:

final client = WinHttpClient.fromConfiguration(
  WinHttpClientConfiguration(
    userAgent: 'MyApp/1.0',
    connectTimeout: Duration(seconds: 10),
    receiveTimeout: Duration(seconds: 30),
  ),
);

Proxy configuration

By default, WinHttpClient uses automatic proxy detection (WinHttpAccessType.automatic). You can configure a named proxy:

final client = WinHttpClient.fromConfiguration(
  WinHttpClientConfiguration(
    accessType: WinHttpAccessType.named,
    proxy: 'proxy.example.com:8080',
    proxyBypass: 'localhost;*.local',
  ),
);

Or disable the proxy entirely:

final client = WinHttpClient.fromConfiguration(
  WinHttpClientConfiguration(
    accessType: WinHttpAccessType.noProxy,
  ),
);

Supported features

Feature	Status
HTTP/HTTPS	Supported
GET, POST, PUT, PATCH, DELETE, HEAD	Supported
Request headers	Supported
Response streaming	Supported
Redirect following	Supported (configurable)
Gzip/deflate decompression	Automatic
System proxy (WPAD/PAC)	Automatic
TLS via Windows Schannel	Automatic
Cookies	Per-request only (no cross-request cookie jar)
Abort/cancel	Partial (response-stream abort works; pre-send abort requires async WinHTTP)
Streaming request body	Not supported (body materialized in memory)

Known limitations

• Request bodies are buffered in memory. The entire request body is materialized before sending, similar to cronet_http. This is fine for typical API payloads but not ideal for multi-GB uploads.

• Headers persist across redirects. WinHTTP transfers request headers (including Authorization) across redirect hops. Be cautious with sensitive headers when following redirects to untrusted domains.

• Folded headers. WinHTTP handles RFC 2822 folded headers internally but normalizes whitespace differently than some clients expect.