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


Dio is a networking library developed by Flutter China. It’s a robust Dart HTTP client that includes features like Interceptors, global configuration, FormData, Request Cancellation, File Downloading, and ConnectionTimeout. Things that dio enables can be done using a regular http library, which we also receive with the flutter sdk, but it’s not as simple to learn or comprehend, so dio is preferable.
Dart’s Dio is a robust HTTP client. Interceptors, global configuration, FormData, request cancellation, file downloading, and timeout are among the features supported. Flutter has a http package that is useful for basic network activities but can be intimidating to use when dealing with more advanced capabilities.

Get started

Add dependency

  dio: ^4.0.5-beta1

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('http://www.google.com');
  } catch (e) {


A curated list of awesome things related to dio.

Plugins (support 4.x)

dio_cookie_managerA cookie manager for Dio
dio_http2_adapterA Dio HttpClientAdapter which support Http/2.0
dio_smart_retryFlexible retry library for Dio
http_certificate_pinningHttps Certificate pinning for Flutter
curl_logger_dio_interceptorA Flutter curl-command generator for Dio.
dio_http_cacheA simple cache library for Dio like Rxcache in Android
pretty_dio_loggerPretty Dio logger is a Dio interceptor that logs network calls in a pretty, easy to read format.

Related Projects

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


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 dio.post('/test', data: {'id': 12, 'name': 'wendu'});

Performing multiple concurrent requests:

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

Downloading a file:

response = await dio.download('https://www.google.com/', './xx.html');

Get response stream:

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

Sending FormData:

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

Listening the uploading progress:

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

Post binary data by Stream:

// Binary data
List<int> postData = <int>[...];
await dio.post(
  data: Stream.fromIterable(postData.map((e) => [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 = 'https://www.xx.com/api';
dio.options.connectTimeout = 5000; //5s
dio.options.receiveTimeout = 3000;

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

The core API in Dio instance is:

Future request(String path, {data,Map queryParameters, Options options,CancelToken cancelToken, ProgressCallback onSendProgress, ProgressCallback onReceiveProgress)

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 get(…)

Future post(…)

Future put(…)

Future delete(…)

Future head(…)

Future put(…)

Future path(…)

Future download(…)

Future fetch(RequestOptions) 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: 'https://www.google.com/api/'.
  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('https://www.google.com');


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 handler.next(options); //continue
     // If you want to resolve the request with some custom data,
     // you can resolve a `Response` object eg: `handler.resolve(response)`.
     // If you want to reject the request with a error message,
     // you can reject a `DioError` object eg: `handler.reject(dioError)`
    onResponse:(response,handler) {
     // Do something with response data
     return handler.next(response); // continue
     // If you want to reject the request with a error message,
     // you can reject a `DioError` object eg: `handler.reject(dioError)` 
    onError: (DioError e, handler) {
     // Do something with response error
     return  handler.next(e);//continue
     // If you want to resolve the request with some custom data,
     // you can resolve a `Response` object eg: `handler.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: ${response.requestOptions.path}');
    return super.onResponse(response, handler);
  Future onError(DioError err, ErrorInterceptorHandler handler) {
    print('ERROR[${err.response?.statusCode}] => PATH: ${err.requestOptions.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 call handler.resolve(Response). If you want to reject the request/response with a error message, you can call handler.reject(dioError) .

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


Interceptor can be executed concurrently, that is, all of the requests enter the interceptor at once, rather than executing sequentially. However, in some cases we expect that requests enter the interceptor sequentially like #590 。 Therefore, we need to provide a mechanism for sequential access(one by one) to interceptors and QueuedInterceptor can solve this problem.


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:

  var dio = Dio();
  //  dio instance to request token
  var tokenDio = Dio();
  String? csrfToken;
  dio.options.baseUrl = 'http://www.dtworkroom.com/doris/1/2.0.0/';
  tokenDio.options = dio.options;
    onRequest: (options, handler) {
      print('send request:path:${options.path},baseURL:${options.baseUrl}');
      if (csrfToken == null) {
        print('no token,request token firstly...');
        tokenDio.get('/token').then((d) {
          options.headers['csrfToken'] = csrfToken = d.data['data']['token'];
          print('request token succeed, value: ' + d.data['data']['token']);
              'continue to perform request:path:${options.path},baseURL:${options.path}');
        }).catchError((error, stackTrace) {
          handler.reject(error, true);
      } else {
        options.headers['csrfToken'] = csrfToken;
        return handler.next(options);

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

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/QueuedInterceptor 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('https://wendux.github.io/xsddddd');
} 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 != null) {
  } 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 dio.post('/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 https://flutterchina.club , and the license is MIT.


Source Code: flutter_dio.

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