Development and Hot Reload Middleware for Koa2
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Development and Hot Module Reload Middleware for Koa2, in a single middleware module.

This module wraps and composes webpack-dev-middleware and webpack-hot-client into a single middleware module, allowing for quick and concise implementation.

As an added bonus, it'll also use the installed webpack module from your project, and the webpack.config.js file in the root of your project, automagically, should you choose to let it. This negates the need for all of the repetitive setup and config that you get with koa-webpack-middleware.


Using npm:

npm install koa-webpack --save-dev


koa-webpack is an evergreen module. 🌲 This module requires an Active LTS Node version (v8.0.0+ or v10.0.0+), and Webpack v4.0.0+.


const Koa = require('koa');
const koaWebpack = require('koa-webpack');

const app = new Koa();
const options = { .. };
const middleware = await koaWebpack(options);




Returns a Promise which resolves the server middleware containing the following additional properties:

  • close(callback) (Function) - Closes both the instance of webpack-dev-middleware and webpack-hot-client. Accepts a single Function callback parameter that is executed when complete.
  • hotClient (Object) - An instance of webpack-hot-client.
  • devMiddleware (Object) - An instance of webpack-dev-middleware


The middleware accepts an options Object, which can contain options for the webpack-dev-middleware and webpack-hot-client bundled with this module. The following is a property reference for the Object:


Type: Object

Should you rather that the middleware use an instance of webpack that you've already init'd [with webpack config], you can pass it to the middleware using this option.


const webpack = require('webpack');
const config = require('./webpack.config.js');
const koaWebpack = require('koa-webpack');

const compiler = Webpack(config);
const middleware = await koaWebpack({ compiler });



Type: Object

Should you rather that the middleware use an instance of webpack configuration that you've already required/imported, you can pass it to the middleware using this option.


const koaWebpack = require('koa-webpack');
const config = require('./webpack.config.js');

const middleware = await koaWebpack({ config });



Type: Object

The devMiddleware property should contain options for webpack-dev-middleware, a list of which is available at webpack-dev-middleware. Omitting this property will result in webpack-dev-middleware using its default options.


Type: Object|Boolean

The hotClient property should contain options for webpack-hot-client, a list of which is available at webpack-hot-client. Omitting this property will result in webpack-hot-client using its default options.

As of v3.0.1 setting this to false will completely disable webpack-hot-client and all automatic Hot Module Replacement functionality.

Using with koa-compress

When using koa-webpack with koa-compress, you may experience issues with saving files and hot module reload. Please review this issue for more information and a workaround.


When serverSideRender is set to true in config.devMiddleware, webpackStats is accessible from ctx.state.webpackStats.

app.use(async (ctx, next) => {
  const assetsByChunkName = ctx.state.webpackStats.toJson().assetsByChunkName;
  // do something with assetsByChunkName

For more details please refer to: webpack-dev-middleware

Using with html-webpack-plugin

When using with html-webpack-plugin, you can access dev-middleware in-memory filesystem to serve index.html file:

const middleware = await koaWebpack({ config });


app.use(async (ctx) => {
  const filename = path.resolve(webpackConfig.output.path, 'index.html')
  ctx.response.type = 'html'
  ctx.response.body = middleware.devMiddleware.fileSystem.createReadStream(filename)


Please take a moment to read our contributing guidelines if you haven't yet done so.



This module started as a fork of koa-webpack-middleware