Frequently Asked Questions

Where are Babel, Prettier and ESLint configured?

ESLint, Babel and Prettier all have their own config files in the root of the project. Same for Jest and stylelint.

Where are the files coming from when I run npm start?

In development Webpack compiles your application runs it in-memory. Only when you run npm run build will it write to disk and preserve your bundled application across computer restarts.

How do I fix Error: listen EADDRINUSE

This simply means that there's another process already listening on port 3000. The fix is to kill the process and rerun npm start.

OS X / Linux:

  1. Find the process id (PID):

    ps aux | grep node

    This will return the PID as the value following your username:

    janedoe 29811 49.1 2.1 3394936 356956 s004 S+ 4:45pm 2:40.07 node server

    Note: If nothing is listed, you can try lsof -i tcp:3000

  2. Then run

    kill -9 YOUR_PID

    e.g. given the output from the example above, YOUR_PID is 29811, hence that would mean you would run kill -9 29811


  1. Find the process id (PID):

    netstat -a -o -n

    This will return a list of running processes and the ports they're listening on:

    Proto Local Address Foreign Address State PID
    TCP Listening 4196
    TCP Listening 28344
  2. Then run

    taskkill /F /PID YOUR_PID

    e.g. given the output from the example above, YOUR_PID is 28344, hence that would mean you would run taskkill /F /PID 28344

Issue with local caching when running in production mode (F5 / ctrl+F5 / cmd+r weird behavior)

Your production site isn't working? You update the code and nothing changes? It drives you insane?

Quick fix on your local browser:

To fix it on your local browser, just do the following. (Suited when you're testing the production mode locally)

Chrome dev tools > Application > Clear Storage > Clear site data (Chrome)

Full in-depth explanation


Local webfonts not working for development

In development mode CSS sourcemaps require that styling is loaded by blob://, resulting in browsers resolving font files relative to the main document.

A way to use local webfonts in development mode is to add an absolute output.publicPath in, with protocol.

output: {
publicPath: '',
/* … */

Non-route containers

Note: Container will always be nested somewhere below a route. Even if there's dozens of components in between, somewhere up the tree will be route. (maybe only "/", but still a route)

Where do I put the reducer?

While you can include the reducer statically in reducers.js, we don't recommend this as you lose the benefits of code splitting. Instead, add it as a composed reducer. This means that you pass actions onward to a second reducer from a lower-level route reducer like so:

// Main route reducer
function myReducerOfRoute(state, action) {
switch (action.type) {
return someOtherReducer(state, action);

That way, you still get the code splitting at route level, but avoid having a static combineReducers call that includes all of them by default.

See this and the following lesson of the Redux course for more information about reducer composition!

Use CI with bitbucket pipelines

Your project is on bitbucket? Take advantage of the pipelines feature (Continuous Integration) by creating a 'bitbucket-pipelines.yml' file at the root of the project and use the following code to automatically test your app at each commit:

image: gwhansscheuren/bitbucket-pipelines-node-chrome-firefox
- step:
- node --version
- npm --version
- npm install
- npm test

How to keep my project up-to-date with react-boilerplate?

While it's possible to keep your project up-to-date or "in sync" with react-boilerplate, it's usually very difficult and is therefore at your own risk and not recommended. You should not need to do it either, as every version you use will be amazing! There is a long term goal to make this much easier but no ETA at the moment.

How to turn off Webpack performance warnings after production build?

Webpack recommends having those performance hints turned off in development but to keep them on in production. If you still want to disable them, add the next lines to the config in

performance: {
hints: false;

You can find more information about the performance option (how to change maximum allowed size of a generated file, how to exclude some files from being checked and so on) in the Webpack documentation.

Styles getting overridden?

There is a strong chance that your styles are getting imported in the wrong order. Confused? Let me try and explain with an example!

// MyStyledComponent.js
const MyStyledComponent = styled.div`
background-color: green;
/* styles.css */
.alert {
background-color: red;
// ContrivedExample.js
import MyStyledComponent from './MyStyledComponent';
import './styles.css';
const ContrivedExample = props => (
<MyStyledComponent className="alert">{props.children}</MyStyledComponent>

With the magic of webpack, both MyStyledComponent.js and styles.css will each generate a stylesheet that will be injected at the end of <head> and applied to <MyStyledComponent> via the class attribute.

So, will <ContrivedExample> have a green background or a red background?

Applying the rules of specificity, you may think red as styles.css was imported last. Unfortunately, at the time of writing an open issue "CSS resolving order" means you cannot control the order in which the stylesheets are injected. So, with this contrived example, the background could be either green or red.

To resolve the issue, you can either:

1) Increase the specificity of the CSS you want to win

/* styles.css (imported css to win) */
.alert.alert {
background-color: red;
// MyStyledComponent.js (styled-component css to win)
const MyStyledComponent = styled.div`
&& {
background-color: green;

2) Import the CSS in the <head> of your index.html manually

This is a good choice if you are having issues with third-party styles

// Import bootstrap style (e.g. move this into the <head> of index.html)
import 'bootstrap/dist/css/bootstrap.min.css';

3) Change the position of <GlobalStyle> in the rendering of <App>

You can do that inside containers/App/index.js.

More information is available in the official documentation.

Have another question?

Submit an issue, hop onto the Spectrum chat or contact Max direct on twitter!