Migration guide

This document serves as a migration guide for webpack-dev-server@4.0.0.

Before updating

webpack-dev-server v3 and webpack-dev-server v4 automatically apply HotModuleReplacementPlugin plugin when you set hot: true, so please check you don't have HotModuleReplacementPlugin in your plugins if you have hot: true/hot: "only"
webpack-dev-server v3 and webpack-dev-server v4 automatically inject webpack/hot/dev-server in your entry option when you set hot: true (except when you use injectHot for webpack-dev-server v3), please check you don't have webpack/hot/dev-server in your entry option
webpack-dev-server v3 and webpack-dev-server v4 automatically inject webpack-dev-server/client/index.js in your entry option (except when you use injectClient for webpack-dev-server v3), please check you don't have webpack-dev-server/client/index.js in your entry option

⚠ BREAKING CHANGES

Minimum supported Node.js version is 12.13.0.
Minimum supported webpack version is 4.37.0 (but we recommend using webpack >= v5.0.0).
Minimum compatible webpack-cli version is 4.7.0.
The hotOnly option was removed, if you need hot only mode, use { hot: 'only' } value.

v3:

module.exports = {
  devServer: {
    hotOnly: true,
  },
};

v4:

module.exports = {
  devServer: {
    hot: "only",
  },
};

Default web socket server is ws (IE9 does not support web socket, please use { webSocketServer: 'sockjs' }).
The setup option was removed without replacement.
The before option was renamed to onBeforeSetupMiddleware and changed arguments.

v3:

module.exports = {
  devServer: {
    before: function (app, server, compiler) {
      app.get("/some/path", function (req, res) {
        res.json({ custom: "response" });
      });
    },
  },
};

v4:

module.exports = {
  devServer: {
    onBeforeSetupMiddleware: function (devServer) {
      devServer.app.get("/some/path", function (req, res) {
        res.json({ custom: "response" });
      });
    },
  },
};

The after option was renamed to onAfterSetupMiddleware and changed arguments.

v3:

module.exports = {
  devServer: {
    after: function (app, server, compiler) {
      app.get("/some/path", function (req, res) {
        res.json({ custom: "response" });
      });
    },
  },
};

v4:

module.exports = {
  devServer: {
    onAfterSetupMiddleware: function (devServer) {
      devServer.app.get("/some/path", function (req, res) {
        res.json({ custom: "response" });
      });
    },
  },
};

The features option was removed in favor onBeforeSetupMiddleware and onAfterSetupMiddleware options.
The key, cert, pfx, pfx-passphrase, cacert, ca and requestCert options were moved to https options, please use https.{key|cert|pfx|passphrase|requestCert|ca}.

v3:

module.exports = {
  devServer: {
    ca: "./server.pem",
    pfx: "./server.pfx",
    key: "./server.key",
    cert: "./server.crt",
    pfxPassphrase: "webpack-dev-server",
    requestCert: true,
  },
};

v4:

module.exports = {
  devServer: {
    https: {
      ca: "./server.pem",
      pfx: "./server.pfx",
      key: "./server.key",
      cert: "./server.crt",
      passphrase: "webpack-dev-server",
      requestCert: true,
    },
  },
};

The compress option is now true by default.
filename and lazy options were removed in favor experiments.lazyCompilation.
The inline (iframe live mode) option was removed without replacement.
log, logLevel, logTime, quiet, noInfo, and reporter options were removed without replacement, now we use built-in logger.
The useLocalIp option was removed in favor of host: 'local-ip'/'local-ipv4'/'local-ipv6'.

v3:

module.exports = {
  devServer: {
    useLocalIp: true,
  },
};

v4:

module.exports = {
  devServer: {
    host: "local-ip",
  },
};

host/port options can't be null or empty string, please use host: 'local-ip' or port: 'auto'.
the warn option was removed in favor of ignoreWarnings
fs, index, mimeTypes, publicPath, serverSideRender, stats, and writeToDisk (related to webpack-dev-middleware) were moved to devMiddleware option.

v3:

module.exports = {
  devServer: {
    index: true,
    mimeTypes: { "text/html": ["phtml"] },
    publicPath: "/publicPathForDevServe",
    serverSideRender: true,
    writeToDisk: true,
  },
};

v4:

module.exports = {
  devServer: {
    devMiddleware: {
      index: true,
      mimeTypes: { "text/html": ["phtml"] },
      publicPath: "/publicPathForDevServe",
      serverSideRender: true,
      writeToDisk: true,
    },
  },
};

progress/overlay/clientLogLevel option were moved to the client option:

v3:

module.exports = {
  devServer: {
    clientLogLevel: "info",
    overlay: true,
    progress: true,
  },
};

v4:

module.exports = {
  devServer: {
    client: {
      logging: "info",
      // Can be used only for `errors`/`warnings`
      //
      // overlay: {
      //   errors: true,
      //   warnings: true,
      // }
      overlay: true,
      progress: true,
    },
  },
};

public, sockHost, sockPath, and sockPort options were removed in favor client.webSocketURL option:

v3:

module.exports = {
  devServer: {
    public: "ws://localhost:8080",
  },
};

module.exports = {
  devServer: {
    sockHost: "0.0.0.0",
    sockPath: "/ws",
    sockPort: 8080,
  },
};

v4:

module.exports = {
  devServer: {
    client: {
      // Can be `string`:
      //
      // To get protocol/hostname/port from browser
      // webSocketURL: 'auto://0.0.0.0:0/ws'
      webSocketURL: {
        hostname: "0.0.0.0",
        pathname: "/ws",
        port: 8080,
      },
    },
  },
};

If you need to set custom path to dev server web socket server, please use:

module.exports = {
  devServer: {
    webSocketServer: {
      options: {
        path: "/my/custom/path/to/web/socket/server",
      },
    },
  },
};

client.overlay (previously the overlay option ) is now true by default.
contentBase/contentBasePublicPath/serveIndex/watchContentBase/watchOptions/staticOptions options were moved to static option:

v3:

module.exports = {
  devServer: {
    contentBase: path.join(__dirname, "public"),
    contentBasePublicPath: "/serve-content-base-at-this-url",
    serveIndex: true,
    watchContentBase: true,
    watchOptions: {
      poll: true,
    },
  },
};

v4:

module.exports = {
  devServer: {
    static: {
      directory: path.resolve(__dirname, "static"),
      staticOptions: {},
      // Don't be confused with `devMiddleware.publicPath`, it is `publicPath` for static directory
      // Can be:
      // publicPath: ['/static-public-path-one/', '/static-public-path-two/'],
      publicPath: "/static-public-path/",
      // Can be:
      // serveIndex: {} (options for the `serveIndex` option you can find https://github.com/expressjs/serve-index)
      serveIndex: true,
      // Can be:
      // watch: {} (options for the `watch` option you can find https://github.com/paulmillr/chokidar)
      watch: true,
    },
  },
};

Provide an array of objects in case you have multiple static folders:

module.exports = {
  //...
  devServer: {
    static: [
      {
        directory: path.join(__dirname, "assets"),
        publicPath: "/serve-public-path-url",
      },
      {
        directory: path.join(__dirname, "css"),
        publicPath: "/other-serve-public-path-url",
      },
    ],
  },
};

Default value of the static option is path.resolve(process.cwd(), 'public') directory and enabled by default.
static.watch is enabled by default.
The socket option was renamed to ipc (also supports string type, i.e. path to unix socket):

v3:

module.exports = {
  devServer: {
    socket: true,
  },
};

v4:

module.exports = {
  devServer: {
    ipc: true,
  },
};

The disableHostCheck option was removed in favor allowedHosts: 'all':

v3:

module.exports = {
  devServer: {
    disableHostCheck: true,
  },
};

v4:

module.exports = {
  devServer: {
    allowedHosts: "all",
  },
};

open and openPage options were unionized in favor of the open option:

v3:

module.exports = {
  devServer: {
    // openPage: '/my-page',
    openPage: true,
  },
};

v4:

module.exports = {
  devServer: {
    // open: ['/my-page'],
    open: true,
  },
};

module.exports = {
  devServer: {
    open: {
      target: ["first.html", `http://localhost:8080/second.html`],
      app: {
        name: "google-chrome",
        arguments: ["--incognito", "--new-window"],
      },
    },
  },
};

transportMode (i.e. transportMode.client/transportMode.server options) were removed in favor of client.webSocketTransport and webSocketServer:

v3:

module.exports = {
  transportMode: "ws",
};

module.exports = {
  transportMode: {
    client: require.resolve("./CustomClient"),
    server: require.resolve("./CustomServer"),
  },
};

v4:

module.exports = {
  devServer: {
    // webSocketServer: 'sockjs',
    webSocketServer: "ws",
  },
};

module.exports = {
  devServer: {
    client: {
      webSocketTransport: require.resolve("./CustomClient"),
    },
    webSocketServer: require.resolve("./CustomServer"),
  },
};

(webpack-dev-middleware)[https://github.com/webpack/webpack-dev-middleware] was update to v5.
All options can be set via CLI, don't forget if you need to override option from configuration(s) you should use reset flag, i.e. --static-reset --static my-directory
Many CLI options were renamed in favor of the above change, please use webpack serve --help to get a list of them.
The stdin option was removed in favor of --watch-options-stdin.

injectClient and injectHot were removed in favor of manual setup entries.

injectClient: false was replaced with client: false:

v3:

module.exports = {
  devServer: {
    injectClient: false,
  },
};

v4:

module.exports = {
  devServer: {
    client: false,
  },
};

injectHot: false is now assumed when hot: false is used:

v3:

module.exports = {
  devServer: {
    injectHot: false,
  },
};

v4:

module.exports = {
  devServer: {
    hot: false,
  },
};

The sockWrite public method was renamed to sendMessage.
The profile option was removed in favor ProfilingPlugin.

The addDevServerEntrypoints method was removed in favor of manual configuration.

v4:

const webpack = require("webpack");
const DevServer = require("webpack-dev-server");

const config = {
  entry: [
    // Runtime code for hot module replacement
    "webpack/hot/dev-server.js",
    // Dev server client for web socket transport, hot and live reload logic
    "webpack-dev-server/client/index.js?hot=true&live-reload=true",
    // Your entry
    "./src/entry.js",
  ],
  plugin: [
    // Plugin for hot module replacement
    new webpack.HotModuleReplacementPlugin(),
  ],
};
const compiler = webpack(config);
// `hot` and `client` options are disabled because we added them manually
const server = new DevServer({ hot: false, client: false }, compiler);

(async () => {
  await server.start();

  console.log("Running");
})();

Deprecations

constructor arguments were changed, the first argument is dev server options, the second is compiler

v3:

const devServerOptions = { host: "127.0.0.1", port: 8080 };
const devServer = new Server(compiler, devServerOptions);

v4:

const devServerOptions = { host: "127.0.0.1", port: 8080 };
const devServer = new Server(devServerOptions, compiler);

listen method is deprecated in favor async start or startCallback methods

v3:

const devServerOptions = { host: "127.0.0.1", port: 8080 };
const devServer = new Server(compiler, devServerOptions);

devServer.listen(devServerOptions.host, devServerOptions.port, () => {
  console.log("Running");
});

v4:

const devServerOptions = { host: "127.0.0.1", port: 8080 };
const devServer = new Server(devServerOptions, compiler);

(async () => {
  await devServer.start();

  console.log("Running");
})();

const devServerOptions = { host: "127.0.0.1", port: 8080 };
const devServer = new Server(devServerOptions, compiler);

devServer.startCallback(() => {
  console.log("Running");
});

close method is deprecated in favor async stop or stopCallback methods

v3:

const devServerOptions = { host: "127.0.0.1", port: 8080 };
const devServer = new Server(compiler, devServerOptions);

devServer.listen(devServerOptions.host, devServerOptions.port, () => {
  console.log("Running");

  devServer.close(() => {
    console.log("Closed");
  });
});

v4:

const devServerOptions = { host: "127.0.0.1", port: 8080 };
const devServer = new Server(devServerOptions, compiler);

(async () => {
  await devServer.start();

  console.log("Running");

  await devServer.stop();

  console.log("Closed");
})();

const devServerOptions = { host: "127.0.0.1", port: 8080 };
const devServer = new Server(devServerOptions, compiler);

devServer.startCallback(() => {
  console.log("Running");

  devServer.stopCallback(() => {
    console.log("Closed");
  });
});

Features

Added the setupExitSignals option, it takes a boolean and if true (default on CLI), the server will close and exit the process on SIGINT and SIGTERM.
Print a warning if the host/port option and the host/port argument passed to server.listen() are different.
Allowed to disable web socket server using webSocketServer: false.
Added the watchFiles option, now you can reload server on file changes, for example { watchFiles: ["src/**/*.php", "public/**/*"] }.
You can specify multiple targets and browsers for the open option, i.e. { open: { target: ['/my-page', '/my-other-page'], app: ['google-chrome', '--incognito'] } }, also you can use { open: { target: '<url>', app: ['google-chrome', '--incognito'] } } to open default URL in multiple browsers.
Support bonjour options.
The headers option can be Function type.
Overlay can be closed in browser.
The allowedHosts option can be auto or custom string with your domain (i.e. default value).
The static option can be disabled using static: false.
Added async start and stop methods to API
Added startCallback and stopCallback methods to API
Migrate on built-in webpack logger.

Bug Fixes

Compatibility with the target option (you can use target: ['web', 'es5']).
publicPath: auto is now working out of box.
No problems with the target option anymore, you can remove workaround (i.e. target: 'web' for webpack v5).
Fix webpack-dev-server binary, i.e. webpack server and webpack-dev-server will work identically.
Empty and multiple entries support.
IPv6 supported.
chokidar was updated.
Respect the client.logging option for HMR logging.
Show plugin name in progress log.
Use value of the infrastructureLogging.level option by default for client.logging.
Allow to pass options without the target option for the proxy options.
Support lazy compilation.

There are a lot of other bug fixes.

Notes

Compatibility with IE11/IE10/IE9:

For IE11/IE10 you need polyfill fetch() and Promise, example:

module.exports = {
  entry: {
    entry: ["whatwg-fetch", "core-js/features/promise", "./entry.js"],
  },
};

For IE9 you need polyfill fetch() and Promise and use sockjs for communications (because WebSocket is not supported), example:

module.exports = {
  entry: {
    entry: ["whatwg-fetch", "core-js/features/promise", "./entry.js"],
  },
  devServer: {
    webSocketServer: "sockjs",
  },
};

IE8 is not supported, sorry

Change in Node.js API:
- If you're using dev-server through the Node.js API, the options in devServer will be ignored. Pass the options as a first parameter instead:
v3:
```
new WebpackDevServer(compiler, {...})
```
v4:
```
new WebpackDevServer({...}, compiler)
```
- See here for an example of how to use webpack-dev-server through the Node.js API.

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Migration guide

Before updating

⚠ BREAKING CHANGES

Deprecations

Features

Bug Fixes

Notes

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Migration guide

Before updating

⚠ BREAKING CHANGES

Deprecations

Features

Bug Fixes

Notes