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A powerful Http client for Dart, which supports Interceptors, Global configuration, FormData, Request Cancellation, File downloading, Timeout etc.

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Add dependency

  dio: ^4.0.0

Already know Dio 3 and just want to learn about what's new in Dio 4? Check out the Migration Guide!

Super simple to use

import 'package:dio/dio.dart';
void getHttp() async {
  try {
    var response = await Dio().get('');
  } catch (e) {


🎉 A curated list of awesome things related to dio.


dio_cookie_managerPubA cookie manager for Dio
dio_http2_adapterPubA Dio HttpClientAdapter which support Http/2.0
dio_flutter_transformerPubA Dio transformer especially for flutter, by which the json decoding will be in background with compute function.
dio_http_cachePubA cache library for Dio, like Rxcache in Android. dio-http-cache uses sqflite as disk cache, and LRU strategy as memory cache.
retrofitPubretrofit.dart is an dio client generator using source_gen and inspired by Chopper and Retrofit.
dio_firebase_performancePubA Dio Interceptor for reporting network metrics to Firebase
postman_dioPubA Dio Logger Interceptor for export to 'Postman Collection'.json

Related Projects

Welcome to submit Dio's third-party plugins and related libraries here .

Table of contents


Performing a GET request:

Response response;
var dio = Dio();
response = await dio.get('/test?id=12&name=wendu');
// Optionally the request above could also be done as
response = await dio.get('/test', queryParameters: {'id': 12, 'name': 'wendu'});

Performing a POST request:

response = await'/test', data: {'id': 12, 'name': 'wendu'});

Performing multiple concurrent requests:

response = await Future.wait(['/info'), dio.get('/token')]);

Downloading a file:

response = await'', './xx.html');

Get response stream:

Response<ResponseBody> rs;
rs = await Dio().get<ResponseBody>(url,
  options: Options(responseType:,  // set responseType to `stream`
print(; //response stream

Get response with bytes:

Response<List<int>> rs 
rs = await Dio().get<List<int>>(url,
 options: Options(responseType: ResponseType.bytes), // set responseType to `bytes`
print(; // List<int>

Sending FormData:

var formData = FormData.fromMap({
  'name': 'wendux',
  'age': 25,
var response = await'/info', data: formData);

Uploading multiple files to server by FormData:

var formData = FormData.fromMap({
  'name': 'wendux',
  'age': 25,
  'file': await MultipartFile.fromFile('./text.txt', filename: 'upload.txt'),
  'files': [
    await MultipartFile.fromFile('./text1.txt', filename: 'text1.txt'),
    await MultipartFile.fromFile('./text2.txt', filename: 'text2.txt'),
var response = await'/info', data: formData);

Listening the uploading progress:

response = await
  data: {'aa': 'bb' * 22},
  onSendProgress: (int sent, int total) {
    print('$sent $total');

Post binary data by Stream:

// Binary data
List<int> postData = <int>[...];
  data: Stream.fromIterable( => [e])), //create a Stream<List<int>>
  options: Options(
    headers: {
      Headers.contentLengthHeader: postData.length, // set content-length

…you can find all examples code here.

Dio APIs

Creating an instance and set default configs.

You can create instance of Dio with an optional BaseOptions object:

var dio = Dio(); // with default Options

// Set default configs
dio.options.baseUrl = '';
dio.options.connectTimeout = 5000; //5s
dio.options.receiveTimeout = 3000;

// or new Dio with a BaseOptions instance.
var options = BaseOptions(
  baseUrl: '',
  connectTimeout: 5000,
  receiveTimeout: 3000,
Dio dio = Dio(options);

The core API in Dio instance is:


response = await dio.request(
  data: {'id':12,'name':'xx'},
  options: Options(method:'GET'),

Request method aliases

For convenience aliases have been provided for all supported request methods.









Future new*

Request Options

The Options class describes the http request information and configuration. Each Dio instance has a base config for all requests maked by itself, and we can override the base config with Options when make a single request. The BaseOptions declaration as follows:

  /// Http method.
  String method;

  /// Request base url, it can contain sub path, like: ''.
  String baseUrl;

  /// Http request headers.
  Map<String, dynamic> headers;

   /// Timeout in milliseconds for opening  url.
  int connectTimeout;

   ///  Whenever more than [receiveTimeout] (in milliseconds) passes between two events from response stream,
  ///  [Dio] will throw the [DioError] with [DioErrorType.RECEIVE_TIMEOUT].
  ///  Note: This is not the receiving time limitation.
  int receiveTimeout;

  /// Request data, can be any type.
  T data;

  /// If the `path` starts with 'http(s)', the `baseURL` will be ignored, otherwise,
  /// it will be combined and then resolved with the baseUrl.
  String path='';

  /// The request Content-Type. The default value is 'application/json; charset=utf-8'.
  /// If you want to encode request body with 'application/x-www-form-urlencoded',
  /// you can set [Headers.formUrlEncodedContentType], and [Dio]
  /// will automatically encode the request body.
  String contentType;

  /// [responseType] indicates the type of data that the server will respond with
  /// options which defined in [ResponseType] are `JSON`, `STREAM`, `PLAIN`.
  /// The default value is `JSON`, dio will parse response string to json object automatically
  /// when the content-type of response is 'application/json'.
  /// If you want to receive response data with binary bytes, for example,
  /// downloading a image, use `STREAM`.
  /// If you want to receive the response data with String, use `PLAIN`.
  ResponseType responseType;

  /// `validateStatus` defines whether the request is successful for a given
  /// HTTP response status code. If `validateStatus` returns `true` ,
  /// the request will be perceived as successful; otherwise, considered as failed.
  ValidateStatus validateStatus;

  /// Custom field that you can retrieve it later in [Interceptor]、[Transformer] and the   [Response] object.
  Map<String, dynamic> extra;
  /// Common query parameters
  Map<String, dynamic /*String|Iterable<String>*/ > queryParameters;  
   /// [collectionFormat] indicates the format of collection data in request
  /// options which defined in [CollectionFormat] are `csv`, `ssv`, `tsv`, `pipes`, `multi`,`multiCompatible`.
  /// The default value is `multiCompatible`
  late CollectionFormat collectionFormat;


There is a complete example here.

Response Schema

The response for a request contains the following information.

  /// Response body. may have been transformed, please refer to [ResponseType].
  T? data;
  /// Response headers.
  Headers headers;
  /// The corresponding request info.
  Options request;
  /// Http status code.
  int? statusCode;
  String? statusMessage;
  /// Whether redirect 
  bool? isRedirect;  
  /// redirect info    
  List<RedirectInfo> redirects ;
  /// Returns the final real request uri (maybe redirect). 
  Uri realUri;    
  /// Custom field that you can retrieve it later in `then`.
  Map<String, dynamic> extra;

When request is succeed, you will receive the response as follows:

Response response = await dio.get('');


For each dio instance, We can add one or more interceptors, by which we can intercept requests 、 responses and errors before they are handled by then or catchError.

    onRequest:(options, handler){
     // Do something before request is sent
     return; //continue
     // If you want to resolve the request with some custom data,
     // you can resolve a `Response` object eg: return `dio.resolve(response)`.
     // If you want to reject the request with a error message,
     // you can reject a `DioError` object eg: return `dio.reject(dioError)`
    onResponse:(response,handler) {
     // Do something with response data
     return; // continue
     // If you want to reject the request with a error message,
     // you can reject a `DioError` object eg: return `dio.reject(dioError)` 
    onError: (DioError e, handler) {
     // Do something with response error
     // If you want to resolve the request with some custom data,
     // you can resolve a `Response` object eg: return `dio.resolve(response)`.  

Simple interceptor example:

import 'package:dio/dio.dart';
class CustomInterceptors extends Interceptor {
  void onRequest(RequestOptions options, RequestInterceptorHandler handler) {
    print('REQUEST[${options.method}] => PATH: ${options.path}');
    return super.onRequest(options, handler);
  Future onResponse(Response response, ResponseInterceptorHandler handler) {
    print('RESPONSE[${response.statusCode}] => PATH: ${response.request?.path}');
    return super.onResponse(response, handler);
  Future onError(DioError err, ErrorInterceptorHandler handler) {
    print('ERROR[${err.response?.statusCode}] => PATH: ${err.request.path}');
    return super.onError(err, handler);

Resolve and reject the request

In all interceptors, you can interfere with their execution flow. If you want to resolve the request/response with some custom data,you can return a Response object or return dio.resolve(data). If you want to reject the request/response with a error message, you can return a DioError object or return dio.reject(errMsg) .

  onRequest:(options, handler) {
   return handler.resolve(Response(requestOptions:options,data:'fake data'));
Response response = await dio.get('/test');
print(;//'fake data'

Lock/unlock the interceptors

You can lock/unlock the interceptors by calling their lock()/unlock method. Once the request/response interceptor is locked, the incoming request/response will be added to a queue before they enter the interceptor, they will not be continued until the interceptor is unlocked.

tokenDio = Dio(); //Create a new instance to request the token.
tokenDio.options = dio.options.copyWith();
  onRequest:(Options options, handler){
    // If no token, request token firstly and lock this interceptor
    // to prevent other request enter this interceptor.
    // We use a new Dio(to avoid dead lock) instance to request token.
       //Set the token to headers
       options.headers['token'] =['data']['token'];; //continue
    }).catchError((error, stackTrace) {
       handler.reject(error, true);
    }).whenComplete(() => dio.interceptors.requestLock.unlock());

You can clean the waiting queue by calling clear();


When the request interceptor is locked, the incoming request will pause, this is equivalent to we locked the current dio instance, Therefore, Dio provied the two aliases for the lock/unlock of request interceptors.

dio.lock() == dio.interceptors.requestLock.lock()

dio.unlock() == dio.interceptors.requestLock.unlock()

dio.clear() == dio.interceptors.requestLock.clear()


Because of security reasons, we need all the requests to set up a csrfToken in the header, if csrfToken does not exist, we need to request a csrfToken first, and then perform the network request, because the request csrfToken progress is asynchronous, so we need to execute this async request in request interceptor. The code is as follows:

  onRequest: (Options options, handler) async {
    print('send request:path:${options.path},baseURL:${options.baseUrl}');
    if (csrfToken == null) {
      print('no token,request token firstly...');
      //lock the dio.
      tokenDio.get('/token').then((d) {
        options.headers['csrfToken'] = csrfToken =['data']['token'];
        print('request token succeed, value: ' +['data']['token']);
        print( 'continue to perform request:path:${options.path},baseURL:${options.path}');;
      }).catchError((error, stackTrace) {
        handler.reject(error, true);
      }) .whenComplete(() => dio.unlock()); // unlock the dio
    } else {
      options.headers['csrfToken'] = csrfToken;;

For complete codes click here.


You can set LogInterceptor to print request/response log automaticlly, for example:

dio.interceptors.add(LogInterceptor(responseBody: false)); //开启请求日志

Custom Interceptor

You can custom interceptor by extending the Interceptor class. There is an example that implementing a simple cache policy: custom cache interceptor.

Cookie Manager

dio_cookie_manager package is a cookie manager for Dio.

Handling Errors

When a error occurs, Dio will wrap the Error/Exception to a DioError:

try {
  await dio.get('');
} on DioError catch (e) {
  // The request was made and the server responded with a status code
  // that falls out of the range of 2xx and is also not 304.
  if (e.response) {
  } else {
    // Something happened in setting up or sending the request that triggered an Error

DioError scheme

  /// Response info, it may be `null` if the request can't reach to
  /// the http server, for example, occurring a dns error, network is not available.
  Response? response;
  /// Request info.
  RequestOptions? request;
  /// Error descriptions.
  String message;

  DioErrorType type;
  /// The original error/exception object; It's usually not null when `type`
  /// is DioErrorType.DEFAULT
  dynamic? error;


enum DioErrorType {
  /// It occurs when url is opened timeout.

  /// It occurs when url is sent timeout.

  ///It occurs when receiving timeout.

  /// When the server response, but with a incorrect status, such as 404, 503...

  /// When the request is cancelled, dio will throw a error with this type.

  /// Default error type, Some other Error. In this case, you can
  /// use the DioError.error if it is not null.

Using application/x-www-form-urlencoded format

By default, Dio serializes request data(except String type) to JSON. To send data in the application/x-www-form-urlencoded format instead, you can :

//Instance level
dio.options.contentType= Headers.formUrlEncodedContentType;
//or works once
  data: {'id': 5},
  options: Options(contentType: Headers.formUrlEncodedContentType),

Sending FormData

You can also send FormData with Dio, which will send data in the multipart/form-data, and it supports uploading files.

var formData = FormData.fromMap({
  'name': 'wendux',
  'age': 25,
  'file': await MultipartFile.fromFile('./text.txt',filename: 'upload.txt')
response = await'/info', data: formData);

There is a complete example here.

Multiple files upload

There are two ways to add multiple files to FormData, the only difference is that upload keys are different for array types。

  'files': [
    MultipartFile.fromFileSync('./example/upload.txt', filename: 'upload.txt'),
    MultipartFile.fromFileSync('./example/upload.txt', filename: 'upload.txt'),

The upload key eventually becomes 'files[]',This is because many back-end services add a middle bracket to key when they get an array of files. If you don't want “[]”,you should create FormData as follows(Don't use FormData.fromMap):

var formData = FormData();
    MultipartFile.fromFileSync('./example/upload.txt',filename: 'upload.txt'),
    MultipartFile.fromFileSync('./example/upload.txt',filename: 'upload.txt'),


Transformer allows changes to the request/response data before it is sent/received to/from the server. This is only applicable for request methods 'PUT', 'POST', and 'PATCH'. Dio has already implemented a DefaultTransformer, and as the default Transformer. If you want to customize the transformation of request/response data, you can provide a Transformer by your self, and replace the DefaultTransformer by setting the dio.transformer.

In flutter

If you use dio in flutter development, you'd better to decode json in background with compute function.

// Must be top-level function
_parseAndDecode(String response) {
  return jsonDecode(response);

parseJson(String text) {
  return compute(_parseAndDecode, text);

void main() {
  //Custom jsonDecodeCallback
  (dio.transformer as DefaultTransformer).jsonDecodeCallback = parseJson;

Other Example

There is an example for customizing Transformer.


HttpClientAdapter is a bridge between Dio and HttpClient.

Dio implements standard and friendly API for developer.

HttpClient: It is the real object that makes Http requests.

We can use any HttpClient not just dart:io:HttpClient to make the Http request. And all we need is providing a HttpClientAdapter. The default HttpClientAdapter for Dio is DefaultHttpClientAdapter.

dio.httpClientAdapter = new DefaultHttpClientAdapter();

Here is a simple example to custom adapter.

Using proxy

DefaultHttpClientAdapter provide a callback to set proxy to dart:io:HttpClient, for example:

import 'package:dio/dio.dart';
import 'package:dio/adapter.dart';
(dio.httpClientAdapter as DefaultHttpClientAdapter).onHttpClientCreate = (client) {
  // config the http client
  client.findProxy = (uri) {
    //proxy all request to localhost:8888
    return 'PROXY localhost:8888';
  // you can also create a new HttpClient to dio
  // return HttpClient();

There is a complete example here.

Https certificate verification

There are two ways to verify the https certificate. Suppose the certificate format is PEM, the code like:

String PEM='XXXXX'; // certificate content
(dio.httpClientAdapter as DefaultHttpClientAdapter).onHttpClientCreate  = (client) {
  client.badCertificateCallback=(X509Certificate cert, String host, int port){
    if(cert.pem==PEM){ // Verify the certificate
      return true;
    return false;

Another way is creating a SecurityContext when create the HttpClient:

(dio.httpClientAdapter as DefaultHttpClientAdapter).onHttpClientCreate  = (client) {
  SecurityContext sc = SecurityContext();
  //file is the path of certificate
  HttpClient httpClient = HttpClient(context: sc);
  return httpClient;

In this way, the format of certificate must be PEM or PKCS12.

Http2 support

dio_http2_adapter package is a Dio HttpClientAdapter which support Http/2.0 .


You can cancel a request using a cancel token. One token can be shared with multiple requests. When a token's cancel method invoked, all requests with this token will be cancelled.

CancelToken token = CancelToken();
dio.get(url, cancelToken: token)
   .catchError((DioError err){
    if (CancelToken.isCancel(err)) {
      print('Request canceled! '+ err.message)
      // handle error.
// cancel the requests with "cancelled" message.

There is a complete example here.

Extends Dio class

Dio is a abstract class with factory constructor,so we don't extend Dio class directy. For this purpose, we can extend DioForNative or DioForBrowser instead, for example:

import 'package:dio/dio.dart';
import 'package:dio/native_imp.dart'; //If in browser, import 'package:dio/browser_imp.dart'

class Http extends DioForNative {
  Http([BaseOptions options]):super(options){
    // do something

We can also implement our Dio client:

class MyDio with DioMixin implements Dio{
  // ...

Copyright & License

This open source project authorized by , and the license is MIT.

Features and bugs

Please file feature requests and bugs at the issue tracker.


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A powerful Http client for Dart, which supports Interceptors, Global configuration, FormData, File downloading etc. and Dio is very easy to use. [...]