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https://github.com/chimurai/http-proxy-middleware

:zap: The one-liner node.js http-proxy middleware for connect, express, next.js and more
https://github.com/chimurai/http-proxy-middleware

browser-sync connect express fastify http-proxy javascript middleware nextjs node nodejs polka proxy proxy-middleware websocket

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:zap: The one-liner node.js http-proxy middleware for connect, express, next.js and more

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# http-proxy-middleware



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Node.js proxying made simple. Configure proxy middleware with ease for [connect](https://github.com/senchalabs/connect), [express](https://github.com/expressjs/express), [next.js](https://github.com/vercel/next.js) and [many more](#compatible-servers).



Powered by the popular Nodejitsu [`http-proxy`](https://github.com/http-party/node-http-proxy). [![GitHub stars](https://img.shields.io/github/stars/http-party/node-http-proxy.svg?style=social&label=Star)](https://github.com/http-party/node-http-proxy)



## ⚠️ Note 



This page is showing documentation for version v3.x.x ([release notes](https://github.com/chimurai/http-proxy-middleware/releases))



See [MIGRATION.md](https://github.com/chimurai/http-proxy-middleware/blob/master/MIGRATION.md) for details on how to migrate from v2.x.x to v3.x.x



If you're looking for older documentation. Go to:



- 

- 



## TL;DR 



Proxy `/api` requests to `http://www.example.org`



:bulb: **Tip:** Set the option `changeOrigin` to `true` for [name-based virtual hosted sites](http://en.wikipedia.org/wiki/Virtual_hosting#Name-based).



```typescript

// typescript



import * as express from 'express';

import type { Request, Response, NextFunction } from 'express';



import { createProxyMiddleware } from 'http-proxy-middleware';

import type { Filter, Options, RequestHandler } from 'http-proxy-middleware';



const app = express();



const proxyMiddleware = createProxyMiddleware({

  target: 'http://www.example.org/api',

  changeOrigin: true,

});



app.use('/api', proxyMiddleware);



app.listen(3000);



// proxy and keep the same base path "/api"

// http://127.0.0.1:3000/api/foo/bar -> http://www.example.org/api/foo/bar

```



_All_ `http-proxy` [options](https://github.com/nodejitsu/node-http-proxy#options) can be used, along with some extra `http-proxy-middleware` [options](#options).



## Table of Contents 



- [Install](#install)

- [Basic usage](#basic-usage)

- [Express Server Example](#express-server-example)

  - [app.use(path, proxy)](#appusepath-proxy)

- [Options](#options)

  - [`pathFilter` (string, \[\]string, glob, \[\]glob, function)](#pathfilter-string-string-glob-glob-function)

  - [`pathRewrite` (object/function)](#pathrewrite-objectfunction)

  - [`router` (object/function)](#router-objectfunction)

  - [`plugins` (Array)](#plugins-array)

  - [`ejectPlugins` (boolean) default: `false`](#ejectplugins-boolean-default-false)

  - [`logger` (Object)](#logger-object)

- [`http-proxy` events](#http-proxy-events)

- [`http-proxy` options](#http-proxy-options)

- [WebSocket](#websocket)

  - [External WebSocket upgrade](#external-websocket-upgrade)

- [Intercept and manipulate requests](#intercept-and-manipulate-requests)

- [Intercept and manipulate responses](#intercept-and-manipulate-responses)

- [Node.js 17+: ECONNREFUSED issue with IPv6 and localhost (#705)](#nodejs-17-econnrefused-issue-with-ipv6-and-localhost-705)

- [Debugging](#debugging)

- [Working examples](#working-examples)

- [Recipes](#recipes)

- [Compatible servers](#compatible-servers)

- [Tests](#tests)

- [Changelog](#changelog)

- [License](#license)



## Install



```shell

npm install --save-dev http-proxy-middleware

```



## Basic usage



Create and configure a proxy middleware with: `createProxyMiddleware(config)`.



```javascript

const { createProxyMiddleware } = require('http-proxy-middleware');



const apiProxy = createProxyMiddleware({

  target: 'http://www.example.org',

  changeOrigin: true,

});



// 'apiProxy' is now ready to be used as middleware in a server.

```



- **options.target**: target host to proxy to. _(protocol + host)_

- **options.changeOrigin**: for virtual hosted sites



- see full list of [`http-proxy-middleware` configuration options](#options)



## Express Server Example



An example with `express` server.



```javascript

// include dependencies

const express = require('express');

const { createProxyMiddleware } = require('http-proxy-middleware');



const app = express();



// create the proxy

/** @type {import('http-proxy-middleware/dist/types').RequestHandler} */

const exampleProxy = createProxyMiddleware({

  target: 'http://www.example.org/api', // target host with the same base path

  changeOrigin: true, // needed for virtual hosted sites

});



// mount `exampleProxy` in web server

app.use('/api', exampleProxy);

app.listen(3000);

```



### app.use(path, proxy)



If you want to use the server's `app.use` `path` parameter to match requests.

Use `pathFilter` option to further include/exclude requests which you want to proxy.



```javascript

app.use(

  createProxyMiddleware({

    target: 'http://www.example.org/api',

    changeOrigin: true,

    pathFilter: '/api/proxy-only-this-path',

  }),

);

```



`app.use` documentation:



- express: 

- connect: 

- polka: 



## Options



http-proxy-middleware options:



### `pathFilter` (string, []string, glob, []glob, function)



Narrow down which requests should be proxied. The `path` used for filtering is the `request.url` pathname. In Express, this is the `path` relative to the mount-point of the proxy.



- **path matching**



  - `createProxyMiddleware({...})` - matches any path, all requests will be proxied when `pathFilter` is not configured.

  - `createProxyMiddleware({ pathFilter: '/api', ...})` - matches paths starting with `/api`



- **multiple path matching**



  - `createProxyMiddleware({ pathFilter: ['/api', '/ajax', '/someotherpath'], ...})`



- **wildcard path matching**



  For fine-grained control you can use wildcard matching. Glob pattern matching is done by _micromatch_. Visit [micromatch](https://www.npmjs.com/package/micromatch) or [glob](https://www.npmjs.com/package/glob) for more globbing examples.



  - `createProxyMiddleware({ pathFilter: '**', ...})` matches any path, all requests will be proxied.

  - `createProxyMiddleware({ pathFilter: '**/*.html', ...})` matches any path which ends with `.html`

  - `createProxyMiddleware({ pathFilter: '/*.html', ...})` matches paths directly under path-absolute

  - `createProxyMiddleware({ pathFilter: '/api/**/*.html', ...})` matches requests ending with `.html` in the path of `/api`

  - `createProxyMiddleware({ pathFilter: ['/api/**', '/ajax/**'], ...})` combine multiple patterns

  - `createProxyMiddleware({ pathFilter: ['/api/**', '!**/bad.json'], ...})` exclusion



  **Note**: In multiple path matching, you cannot use string paths and wildcard paths together.



- **custom matching**



  For full control you can provide a custom function to determine which requests should be proxied or not.



  ```javascript

  /**

   * @return {Boolean}

   */

  const pathFilter = function (path, req) {

    return path.match('^/api') && req.method === 'GET';

  };



  const apiProxy = createProxyMiddleware({

    target: 'http://www.example.org',

    pathFilter: pathFilter,

  });

  ```



### `pathRewrite` (object/function)



Rewrite target's url path. Object-keys will be used as _RegExp_ to match paths.



```javascript

// rewrite path

pathRewrite: {'^/old/api' : '/new/api'}



// remove path

pathRewrite: {'^/remove/api' : ''}



// add base path

pathRewrite: {'^/' : '/basepath/'}



// custom rewriting

pathRewrite: function (path, req) { return path.replace('/api', '/base/api') }



// custom rewriting, returning Promise

pathRewrite: async function (path, req) {

  const should_add_something = await httpRequestToDecideSomething(path);

  if (should_add_something) path += "something";

  return path;

}

```



### `router` (object/function)



Re-target `option.target` for specific requests.



```javascript

// Use `host` and/or `path` to match requests. First match will be used.

// The order of the configuration matters.

router: {

    'integration.localhost:3000' : 'http://127.0.0.1:8001',  // host only

    'staging.localhost:3000'     : 'http://127.0.0.1:8002',  // host only

    'localhost:3000/api'         : 'http://127.0.0.1:8003',  // host + path

    '/rest'                      : 'http://127.0.0.1:8004'   // path only

}



// Custom router function (string target)

router: function(req) {

    return 'http://127.0.0.1:8004';

}



// Custom router function (target object)

router: function(req) {

    return {

        protocol: 'https:', // The : is required

        host: '127.0.0.1',

        port: 8004

    };

}



// Asynchronous router function which returns promise

router: async function(req) {

    const url = await doSomeIO();

    return url;

}

```



### `plugins` (Array)



```js

const simpleRequestLogger = (proxyServer, options) => {

  proxyServer.on('proxyReq', (proxyReq, req, res) => {

    console.log(`[HPM] [${req.method}] ${req.url}`); // outputs: [HPM] GET /users

  });

},



const config = {

  target: `http://example.org`,

  changeOrigin: true,

  plugins: [simpleRequestLogger],

};

```



### `ejectPlugins` (boolean) default: `false`



If you're not satisfied with the pre-configured plugins, you can eject them by configuring `ejectPlugins: true`.



NOTE: register your own error handlers to prevent server from crashing.



```js

// eject default plugins and manually add them back



const {

  debugProxyErrorsPlugin, // subscribe to proxy errors to prevent server from crashing

  loggerPlugin, // log proxy events to a logger (ie. console)

  errorResponsePlugin, // return 5xx response on proxy error

  proxyEventsPlugin, // implements the "on:" option

} = require('http-proxy-middleware');



createProxyMiddleware({

  target: `http://example.org`,

  changeOrigin: true,

  ejectPlugins: true,

  plugins: [debugProxyErrorsPlugin, loggerPlugin, errorResponsePlugin, proxyEventsPlugin],

});

```



### `logger` (Object)



Configure a logger to output information from http-proxy-middleware: ie. `console`, `winston`, `pino`, `bunyan`, `log4js`, etc...



Only `info`, `warn`, `error` are used internally for compatibility across different loggers.



If you use `winston`, make sure to enable interpolation: 



See also logger recipes ([recipes/logger.md](https://github.com/chimurai/http-proxy-middleware/blob/master/recipes/logger.md)) for more details.



```javascript

createProxyMiddleware({

  logger: console,

});

```



## `http-proxy` events



Subscribe to [http-proxy events](https://github.com/nodejitsu/node-http-proxy#listening-for-proxy-events) with the `on` option:



```js

createProxyMiddleware({

  target: 'http://www.example.org',

  on: {

    proxyReq: (proxyReq, req, res) => {

      /* handle proxyReq */

    },

    proxyRes: (proxyRes, req, res) => {

      /* handle proxyRes */

    },

    error: (err, req, res) => {

      /* handle error */

    },

  },

});

```



- **option.on.error**: function, subscribe to http-proxy's `error` event for custom error handling.



  ```javascript

  function onError(err, req, res, target) {

    res.writeHead(500, {

      'Content-Type': 'text/plain',

    });

    res.end('Something went wrong. And we are reporting a custom error message.');

  }

  ```



- **option.on.proxyRes**: function, subscribe to http-proxy's `proxyRes` event.



  ```javascript

  function onProxyRes(proxyRes, req, res) {

    proxyRes.headers['x-added'] = 'foobar'; // add new header to response

    delete proxyRes.headers['x-removed']; // remove header from response

  }

  ```



- **option.on.proxyReq**: function, subscribe to http-proxy's `proxyReq` event.



  ```javascript

  function onProxyReq(proxyReq, req, res) {

    // add custom header to request

    proxyReq.setHeader('x-added', 'foobar');

    // or log the req

  }

  ```



- **option.on.proxyReqWs**: function, subscribe to http-proxy's `proxyReqWs` event.



  ```javascript

  function onProxyReqWs(proxyReq, req, socket, options, head) {

    // add custom header

    proxyReq.setHeader('X-Special-Proxy-Header', 'foobar');

  }

  ```



- **option.on.open**: function, subscribe to http-proxy's `open` event.



  ```javascript

  function onOpen(proxySocket) {

    // listen for messages coming FROM the target here

    proxySocket.on('data', hybridParseAndLogMessage);

  }

  ```



- **option.on.close**: function, subscribe to http-proxy's `close` event.



  ```javascript

  function onClose(res, socket, head) {

    // view disconnected websocket connections

    console.log('Client disconnected');

  }

  ```



## `http-proxy` options



The following options are provided by the underlying [http-proxy](https://github.com/nodejitsu/node-http-proxy#options) library.



- **option.target**: url string to be parsed with the url module

- **option.forward**: url string to be parsed with the url module

- **option.agent**: object to be passed to http(s).request (see Node's [https agent](http://nodejs.org/api/https.html#https_class_https_agent) and [http agent](http://nodejs.org/api/http.html#http_class_http_agent) objects)

- **option.ssl**: object to be passed to https.createServer()

- **option.ws**: true/false: if you want to proxy websockets

- **option.xfwd**: true/false, adds x-forward headers

- **option.secure**: true/false, if you want to verify the SSL Certs

- **option.toProxy**: true/false, passes the absolute URL as the `path` (useful for proxying to proxies)

- **option.prependPath**: true/false, Default: true - specify whether you want to prepend the target's path to the proxy path

- **option.ignorePath**: true/false, Default: false - specify whether you want to ignore the proxy path of the incoming request (note: you will have to append / manually if required).

- **option.localAddress** : Local interface string to bind for outgoing connections

- **option.changeOrigin**: true/false, Default: false - changes the origin of the host header to the target URL

- **option.preserveHeaderKeyCase**: true/false, Default: false - specify whether you want to keep letter case of response header key

- **option.auth** : Basic authentication i.e. 'user:password' to compute an Authorization header.

- **option.hostRewrite**: rewrites the location hostname on (301/302/307/308) redirects.

- **option.autoRewrite**: rewrites the location host/port on (301/302/307/308) redirects based on requested host/port. Default: false.

- **option.protocolRewrite**: rewrites the location protocol on (301/302/307/308) redirects to 'http' or 'https'. Default: null.

- **option.cookieDomainRewrite**: rewrites domain of `set-cookie` headers. Possible values:



  - `false` (default): disable cookie rewriting

  - String: new domain, for example `cookieDomainRewrite: "new.domain"`. To remove the domain, use `cookieDomainRewrite: ""`.

  - Object: mapping of domains to new domains, use `"*"` to match all domains.  

    For example keep one domain unchanged, rewrite one domain and remove other domains:



    ```json

    cookieDomainRewrite: {

      "unchanged.domain": "unchanged.domain",

      "old.domain": "new.domain",

      "*": ""

    }

    ```



- **option.cookiePathRewrite**: rewrites path of `set-cookie` headers. Possible values:



  - `false` (default): disable cookie rewriting

  - String: new path, for example `cookiePathRewrite: "/newPath/"`. To remove the path, use `cookiePathRewrite: ""`. To set path to root use `cookiePathRewrite: "/"`.

  - Object: mapping of paths to new paths, use `"*"` to match all paths.

    For example, to keep one path unchanged, rewrite one path and remove other paths:



    ```json

    cookiePathRewrite: {

      "/unchanged.path/": "/unchanged.path/",

      "/old.path/": "/new.path/",

      "*": ""

    }

    ```



- **option.headers**: object, adds [request headers](https://en.wikipedia.org/wiki/List_of_HTTP_header_fields#Request_fields). (Example: `{host:'www.example.org'}`)

- **option.proxyTimeout**: timeout (in millis) when proxy receives no response from target

- **option.timeout**: timeout (in millis) for incoming requests

- **option.followRedirects**: true/false, Default: false - specify whether you want to follow redirects

- **option.selfHandleResponse** true/false, if set to true, none of the webOutgoing passes are called and it's your responsibility to appropriately return the response by listening and acting on the `proxyRes` event

- **option.buffer**: stream of data to send as the request body. Maybe you have some middleware that consumes the request stream before proxying it on e.g. If you read the body of a request into a field called 'req.rawbody' you could restream this field in the buffer option:



  ```javascript

  'use strict';



  const streamify = require('stream-array');

  const HttpProxy = require('http-proxy');

  const proxy = new HttpProxy();



  module.exports = (req, res, next) => {

    proxy.web(

      req,

      res,

      {

        target: 'http://127.0.0.1:4003/',

        buffer: streamify(req.rawBody),

      },

      next,

    );

  };

  ```



## WebSocket



```javascript

// verbose api

createProxyMiddleware({ pathFilter: '/', target: 'http://echo.websocket.org', ws: true });

```



### External WebSocket upgrade



In the previous WebSocket examples, http-proxy-middleware relies on a initial http request in order to listen to the http `upgrade` event. If you need to proxy WebSockets without the initial http request, you can subscribe to the server's http `upgrade` event manually.



```javascript

const wsProxy = createProxyMiddleware({ target: 'ws://echo.websocket.org', changeOrigin: true });



const app = express();

app.use(wsProxy);



const server = app.listen(3000);

server.on('upgrade', wsProxy.upgrade); // <-- subscribe to http 'upgrade'

```



## Intercept and manipulate requests



Intercept requests from downstream by defining `onProxyReq` in `createProxyMiddleware`.



Currently the only pre-provided request interceptor is `fixRequestBody`, which is used to fix proxied POST requests when `bodyParser` is applied before this middleware.



Example:



```javascript

const { createProxyMiddleware, fixRequestBody } = require('http-proxy-middleware');



const proxy = createProxyMiddleware({

  /**

   * Fix bodyParser

   **/

  on: {

    proxyReq: fixRequestBody,

  },

});

```



## Intercept and manipulate responses



Intercept responses from upstream with `responseInterceptor`. (Make sure to set `selfHandleResponse: true`)



Responses which are compressed with `brotli`, `gzip` and `deflate` will be decompressed automatically. The response will be returned as `buffer` ([docs](https://nodejs.org/api/buffer.html)) which you can manipulate.



With `buffer`, response manipulation is not limited to text responses (html/css/js, etc...); image manipulation will be possible too. ([example](https://github.com/chimurai/http-proxy-middleware/blob/master/recipes/response-interceptor.md#manipulate-image-response))



NOTE: `responseInterceptor` disables streaming of target's response.



Example:



```javascript

const { createProxyMiddleware, responseInterceptor } = require('http-proxy-middleware');



const proxy = createProxyMiddleware({

  /**

   * IMPORTANT: avoid res.end being called automatically

   **/

  selfHandleResponse: true, // res.end() will be called internally by responseInterceptor()



  /**

   * Intercept response and replace 'Hello' with 'Goodbye'

   **/

  on: {

    proxyRes: responseInterceptor(async (responseBuffer, proxyRes, req, res) => {

      const response = responseBuffer.toString('utf8'); // convert buffer to string

      return response.replace('Hello', 'Goodbye'); // manipulate response and return the result

    }),

  },

});

```



Check out [interception recipes](https://github.com/chimurai/http-proxy-middleware/blob/master/recipes/response-interceptor.md#readme) for more examples.



## Node.js 17+: ECONNREFUSED issue with IPv6 and localhost ([#705](https://github.com/chimurai/http-proxy-middleware/issues/705))



Node.js 17+ no longer prefers IPv4 over IPv6 for DNS lookups.

E.g. It's **not** guaranteed that `localhost` will be resolved to `127.0.0.1` – it might just as well be `::1` (or some other IP address).



If your target server only accepts IPv4 connections, trying to proxy to `localhost` will fail if resolved to `::1` (IPv6).



Ways to solve it:



- Change `target: "http://localhost"` to `target: "http://127.0.0.1"` (IPv4).

- Change the target server to (also) accept IPv6 connections.

- Add this flag when running `node`: `node index.js --dns-result-order=ipv4first`. (Not recommended.)



> Note: There’s a thing called [Happy Eyeballs](https://en.wikipedia.org/wiki/Happy_Eyeballs) which means connecting to both IPv4 and IPv6 in parallel, which Node.js doesn’t have, but explains why for example `curl` can connect.



## Debugging



Configure the `DEBUG` environment variable enable debug logging.



See [`debug`](https://github.com/debug-js/debug#readme) project for more options.



```shell

DEBUG=http-proxy-middleware* node server.js



$ http-proxy-middleware proxy created +0ms

$ http-proxy-middleware proxying request to target: 'http://www.example.org' +359ms

```



## Working examples



View and play around with [working examples](https://github.com/chimurai/http-proxy-middleware/tree/master/examples).



- Browser-Sync ([example source](https://github.com/chimurai/http-proxy-middleware/tree/master/examples/browser-sync/index.js))

- express ([example source](https://github.com/chimurai/http-proxy-middleware/tree/master/examples/express/index.js))

- connect ([example source](https://github.com/chimurai/http-proxy-middleware/tree/master/examples/connect/index.js))

- WebSocket ([example source](https://github.com/chimurai/http-proxy-middleware/tree/master/examples/websocket/index.js))

- Response Manipulation ([example source](https://github.com/chimurai/http-proxy-middleware/blob/master/examples/response-interceptor/index.js))



## Recipes



View the [recipes](https://github.com/chimurai/http-proxy-middleware/tree/master/recipes) for common use cases.



## Compatible servers



`http-proxy-middleware` is compatible with the following servers:



- [connect](https://www.npmjs.com/package/connect)

- [express](https://www.npmjs.com/package/express)

- [next.js](https://www.npmjs.com/package/next)

- [fastify](https://www.npmjs.com/package/fastify)

- [browser-sync](https://www.npmjs.com/package/browser-sync)

- [lite-server](https://www.npmjs.com/package/lite-server)

- [polka](https://github.com/lukeed/polka)

- [grunt-contrib-connect](https://www.npmjs.com/package/grunt-contrib-connect)

- [grunt-browser-sync](https://www.npmjs.com/package/grunt-browser-sync)

- [gulp-connect](https://www.npmjs.com/package/gulp-connect)

- [gulp-webserver](https://www.npmjs.com/package/gulp-webserver)



Sample implementations can be found in the [server recipes](https://github.com/chimurai/http-proxy-middleware/tree/master/recipes/servers.md).



## Tests



Run the test suite:



```bash

# install dependencies

$ yarn



# linting

$ yarn lint

$ yarn lint:fix



# building (compile typescript to js)

$ yarn build



# unit tests

$ yarn test



# code coverage

$ yarn cover



# check spelling mistakes

$ yarn spellcheck

```



## Changelog



- [View changelog](https://github.com/chimurai/http-proxy-middleware/blob/master/CHANGELOG.md)



## License



The MIT License (MIT)



Copyright (c) 2015-2024 Steven Chim