browser-run - Easily run code in a browser environment.


The easiest way of running code in a browser environment.

Bundles electronjs by default!

build status downloads


$ echo "console.log('Hey from ' + location); window.close()" | browser-run
Hey from http://localhost:53227/

Or use browser-run programmatically:

var run = require('browser-run');

var browser = run();
browser.end('console.log(location); window.close()');

Example with browserify

$ browserify main.js | browser-run


var browserify = require('browserify');
var browser = require('browser-run');



$ browser-run --help
Run JavaScript in a browser.
Write code to stdin and receive console output on stdout.
Usage: browser-run [OPTIONS]

      --version  Show version number                                   [boolean]
  -b, --browser  Browser to use. Always available: electron. Available if
                 installed: chrome, firefox, ie, safari    [default: "electron"]
      --sandbox  Enable electron sandbox               [boolean] [default: true]
      --basedir  Set this if you need to require node modules in node mode
  -h, --help     Print help                                            [boolean]
  -p, --port     Starts listening on that port and waits for you to open a
  -s, --static   Serve static assets from this directory
  -m, --mock     Path to code to handle requests for mocking a dynamic back-end
  -i, --input    Input type. Defaults to 'javascript', can be set to 'html'.
  -n, --node     Enable nodejs apis in electron

Custom html file

By using --input html or { input: 'html' } you can provide a custom html file for browser-run to use. Keep in mind though that it always needs to have <script src="/reporter.js"></script> above other script tags so browser-run is able to properly forward your console.logs etc to the terminal.

Dynamic back-end mock

By using --mock mock.js or { mock: 'mock.js'} you can provide a custom server-side implementation and handle all requests that are sent to paths beginning with /mock

mock.js needs to export a function that accepts req and res arguments for handling requests.


module.exports = function(req,res){
  if (req.url === '/mock/echo') {



Returns a duplex stream and starts a webserver.

opts can be:

  • port: If speficied, no browser will be started, so you can point one yourself to http://localhost/<port>
  • browser: Browser to use. Defaults to electron. Available if installed:
    • chrome
    • firefox
    • ie
    • safari
  • static: Serve static files from this directory
  • mock: Path to code to handle requests for mocking a dynamic back-end
  • input: Input type. Defaults to javascript, can be set to html.
  • node: Enable nodejs integration in electron
  • sandbox: Enable electron sandbox. Default: true.
  • basedir: Set this if you need to require node modules in node mode

If only an empty string is written to it, an error will be thrown as there is nothing to execute.

If you call window.close() inside the script, the browser will exit.


Stop the underlying webserver.

Headless testing

In environments without a screen, you can use Xvfb to simulate one.

GitHub Actions

This is a full example to run npm test. Refer to the last 2 lines in the YAML config:

  - pull_request
  - push

    runs-on: ubuntu-latest
    - uses: actions/checkout@v1
    - run: npm install
    - run: sudo apt-get install xvfb
    - run: xvfb-run --auto-servernum npm test


Add this to your travis.yml:

      - xvfb
  - export DISPLAY=':99.0'
  - Xvfb :99 -screen 0 1024x768x24 > /dev/null 2>&1 &
  - npm install

Full example.

Any gnu/linux box

$ sudo apt-get install xvfb # or equivalent
$ export DISPLAY=':99.0'
$ Xvfb :99 -screen 0 1024x768x24 > /dev/null 2>&1 &
$ browser-run ...


There is also an example Docker image. Source


With npm do

$ npm install browser-run    # for library
$ npm install -g browser-run # for cli


This module is proudly supported by my Sponsors!

Do you want to support modules like this to improve their quality, stability and weigh in on new features? Then please consider donating to my Patreon. Not sure how much of my modules you're using? Try feross/thanks!



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Jan 28, 2022