Skip to content
A really tiny proxy server which utilizes a service worker
Branch: master
Clone or download
Fetching latest commit…
Cannot retrieve the latest commit at this time.
Type Name Latest commit message Commit time
Failed to load latest commit information.


sw-proxy is a really tiny proxy server which utilizes a service worker. A service worker sits between web applications and the network (when available).

Service workers are able to intercept requests and take an action, like serving a custom response.

This enables you to use sw-proxy as a proxy server inside your browser or as a mock server to test a REST API without having to run a local backend.


Run npm install @dannymoerkerke/sw-proxy --save-dev


Simply add sw-proxy to your web app using a script tag:

<script src="node_modules/sw-proxy/index.js></script>

Then list the requests you want to intercept in an array of objects and save it to sw-proxy-responses.js in the root folder of your application.

For example:

const responses = [
         url: '',
         headers: {
             'Content-Type': 'application/json'
         body: {
             message: 'a json response'
         status: 200,
         statusText: 'OK'
  • url: String (required), fully qualified URL of the request to be proxied
  • method: String (required), HTTP method (GET, POST, PUT or DELETE)
  • headers: Object (optional), key/value pairs of HTTP headers
  • body: Object/String (optional): response body
  • file: String (optional), path to file to be served, relative to root folder of the application. Must be accessible to the web server and will be ignored if body is present
  • status: Number (optional), HTTP status code
  • statusText: String (optional), HTTP status text

Running the demo

Run npm install.

Rename sw-proxy-responses.example.js to sw-proxy-responses.js.

Run npm start.

The demo can now be viewed on http://localhost:8080/demo.

Click the buttons on the demo page to generate the requests and view the results in the dev tools of your browser of choice.

To view the console logs in Safari you need to open a separate Web Inspector window via Develop > Service Workers > localhost.

Browser support

Tested in:

  • Chrome 67+
  • Safari 11.1+
  • Firefox 60+
  • Edge 17+

sw-proxy should run in all browsers that support Service Worker.

Inspecting and debugging the service worker

For a great explanation of how to inspect and debug service workers in Chrome, Firefox, Safari and Edge check Tools for PWA developers.

You can’t perform that action at this time.