Webpack-dev-server doesn't generate source maps

Use webpack-dev-server -d

• -d is shorthand for --debug --devtool source-map --output-pathinfo.

• output-pathinfo adds comments to the generated bundle that explain what module/files are included in what places. So in the generated code, the comment is added to this line of code: require(/* ./test */23) which says that 23 is pointing to the test module. This is mostly helpful when you're looking at the code Webpack has generated, and not so much when stepping through the debugger. I got this example from this relevant bit of documentation.

• This all works because webpack-dev-server accepts all the same flags as webpack.

• See this section in the docs for details.

Tips & gotchas

• --content-base - by default the dev server will serve files in the directory you run the command in. If your build files are in build/, you need to specify --content-base build/ so the dev server will serve up files in the build directory
• --inline - auto-reload whenever you save a file with some changes!

Use webpack -d

The d flag stands for development shortcut and it enables all of your developer tools such as source maps.

Add {devtool:"source-map"} to your webpack.config.js

See more here