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Mock Service Worker Addon Panel
An MSW (Mock Service Worker) addon including a control panel that enables interaction and manipulation of mock requests within Storybook.
npm install storybook-msw-addon
Last updated about 1 month ago
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Storybook Addon for MSW

An MSW (Mock Service Worker) addon including a control panel that enables interaction and manipulation of mock requests within Storybook.


  • Up to date with current MSW version (2.1.0)

Installing and Setup

Install MSW and the addon

With npm:

npm i msw storybook-msw-addon -D

Or with yarn:

yarn add msw storybook-msw-addon -D

Generate service worker for MSW in a project folder.

Keep in mind this influences the paths you can use for your api calls.

npx msw init ${path to project folder to be initialized by msw} --save

For example, the following command will init a service worker inside the api folder of your project.

npx msw init ./api --save

When running Storybook, you have to serve the folder where you have init the MSW service worker as an asset to Storybook. Refer to the docs if needed.

Configure the addon

Enable MSW in Storybook by initializing MSW and providing the MSW loader in ./storybook/preview.js:

import { initialize, mswLoader } from "msw-storybook-addon";

// Initialize MSW

// Provide the MSW addon loader globally. A loader runs before a story renders, avoiding potential race conditions.
export const loaders = [mswLoader];

Start Storybook

Remember to serve the public folder, or the path where you have init the MSW service worker

npm run start-storybook -s ${path to project folder initialized by msw}


The pass request handlers ( into the handlers property of the msw parameter. This is commonly an array of handlers.

import { rest } from "msw";

export const SuccessBehavior = () => <UserProfile />;

SuccessBehavior.parameters = {
  msw: {
    handlers: [
      http.get(endpoint, () => {
        return HttpResponse.json({ results: results });

Advanced Usage

WIP -- Advanced use cases are currently being test with the current version of this addon.

Configuring MSW

If you want to configure storybook-msw--addon, you can pass options to the initialize function.

For example, if you want MSW to bypass unhandled requests you can initialize the addon with the onUnhandledRequest: "bypass" option:

// preview.js
import { initialize } from "msw-storybook-addon";

  onUnhandledRequest: "bypass",

Development scripts

  • yarn start runs babel in watch mode and starts Storybook
  • yarn build build and package your addon code


This addon was inspired both by msw-storybook-addon and storybook-addon-mock, motivating us to combine features of both addons in one place.

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