How do I generate sourcemaps when using babel and webpack?

How do I generate sourcemaps when using babel and webpack?

I’m new to webpack, and I need a hand in setting up to generate sourcemaps. I’m running webpack serve from the command line, which compiles successfully. But I really need sourcemaps. This is my webpack.config.js.
var webpack = require(‘webpack’);

module.exports = {

output: {
filename: ‘main.js’,
publicPath: ‘/assets/’

cache: true,
debug: true,
devtool: true,
entry: [

stats: {
colors: true,
reasons: true

resolve: {
extensions: [”, ‘.js’, ‘.jsx’],
alias: {
‘styles’: __dirname + ‘/src/styles’,
‘mixins’: __dirname + ‘/src/mixins’,
‘components’: __dirname + ‘/src/components/’,
‘stores’: __dirname + ‘/src/stores/’,
‘actions’: __dirname + ‘/src/actions/’
module: {
preLoaders: [{
test: /\.(js|jsx)$/,
exclude: /node_modules/,
loader: ‘jsxhint’
loaders: [{
test: /\.(js|jsx)$/,
exclude: /node_modules/,
loader: ‘react-hot!babel-loader’
}, {
test: /\.sass/,
loader: ‘style-loader!css-loader!sass-loader?outputStyle=expanded&indentedSyntax’
}, {
test: /\.scss/,
loader: ‘style-loader!css!sass’
}, {
test: /\.(png|jpg|woff|woff2)$/,
loader: ‘url-loader?limit=8192’

plugins: [
new webpack.HotModuleReplacementPlugin(),
new webpack.NoErrorsPlugin()


I’m really new to webpack, and looking though the docs hasn’t really helped as I’m not sure what this problem is specific to.


Solution 1:

In order to use source map, you should change devtool option value from true to the value which available in this list, for instance source-map

devtool: 'source-map'

devtool: 'source-map' – A SourceMap is emitted.

Solution 2:

Maybe someone else has this problem at one point. If you use the UglifyJsPlugin in webpack 2 you need to explicitly specify the sourceMap flag. For example:

new webpack.optimize.UglifyJsPlugin({ sourceMap: true })

Solution 3:

Minimal webpack config for jsx with sourcemaps:

var path = require('path');
var webpack = require('webpack');

module.exports = {
  entry: `./src/index.jsx` ,
  output: {
    path:  path.resolve(__dirname,"build"),
    filename: "bundle.js"
  devtool: 'eval-source-map',
  module: {
    loaders: [
        test: /.jsx?$/,
        loader: 'babel-loader',
        exclude: /node_modules/,
        query: {
          presets: ['es2015', 'react']

Running it:

Jozsefs-MBP:react-webpack-babel joco$ webpack -d
Hash: c75d5fb365018ed3786b
Version: webpack 1.13.2
Time: 3826ms
        Asset     Size  Chunks             Chunk Names
    bundle.js   1.5 MB       0  [emitted]  main  1.72 MB       0  [emitted]  main
    + 221 hidden modules
Jozsefs-MBP:react-webpack-babel joco$

Solution 4:

If optimizing for dev + production, you could try something like this in your config:

  devtool: dev ? 'eval-cheap-module-source-map' : 'source-map',

From the docs:

  • devtool: “eval-cheap-module-source-map” offers SourceMaps that only maps lines (no column mappings) and are much faster
  • devtool: “source-map” cannot cache SourceMaps for modules and need to regenerate complete SourceMap for the chunk. It’s something for production.

I am using webpack 2.1.0-beta.19

Solution 5:

On Webpack 2 I tried all 12 devtool options. The following options link to the original file in the console and preserve line numbers. See the note below re: lines only.

devtool best dev options

                                build   rebuild      quality                       look
eval-source-map                 slow    pretty fast  original source               worst
inline-source-map               slow    slow         original source               medium
cheap-module-eval-source-map    medium  fast         original source (lines only)  worst
inline-cheap-module-source-map  medium  pretty slow  original source (lines only)  best

lines only

Source Maps are simplified to a single mapping per line.
This usually means a single mapping per statement (assuming you author is this way).
This prevents you from debugging execution on statement level and from settings breakpoints on columns of a line.
Combining with minimizing is not possible as minimizers usually only emit a single line.


On a large project I find … eval-source-map rebuild time is ~3.5s … inline-source-map rebuild time is ~7s

Solution 6:

Even same issue I faced, in browser it was showing compiled code. I have made below changes in webpack config file and it is working fine now.

 devtool: '#inline-source-map',
 debug: true,

and in loaders I kept babel-loader as first option

loaders: [
    loader: "babel-loader",
    include: [path.resolve(__dirname, "src")]
  { test: /\.js$/, exclude: [/app\/lib/, /node_modules/], loader: 'ng-annotate!babel' },
  { test: /\.html$/, loader: 'raw' },
    test: /\.(jpe?g|png|gif|svg)$/i,
    loaders: [
  {test: /\.less$/, loader: "style!css!less"},
  { test: /\.styl$/, loader: 'style!css!stylus' },
  { test: /\.css$/, loader: 'style!css' }