1.1.3 • Public • Published


This module allows you to create web extension files for Chromium, Google Chrome and all other browsers supporting the file format and API, e.g., Opera.

It creates CRXv3 files, which work for Chrome versions 64.0.3242 and above.

If you need to create web extension file for older browser versions, where CRXv3 is not supported, use CRX module instead.

It requires Node.js version 12 (or above) and runs on Linux, MacOS and Windows.

Build status on Linux & MacOS Build status on Windows


To install CRX3, as with most of the other Node.js modules, use following command line:

npm install crx3

or install it globally:

npm install -g crx3

Usage (CLI)

If you installed CRX3 globally, or you are trying to use it from your project's package.json script(s), you should be able to use it like this:

crx3 web-extension-directory

It supports following options:

  • -z, --zip, --zipPath: create also a simple ZIP file with web extension's files
  • -o, --crx, --crxPath: specify custom path name for CRX3 file
  • -p, --key, --keyPath: specify custom path name for private key file
  • -x, --xml, --xmlPath: specify custom path name for XML (Update Manifest) file
  • --appVersion : specify version number to be written into Update Manifest file
  • --crxURL : specify URL to be written into Update Manifest file
  • --browserVersion : specify minimum browser version required to run web extension

If any of the *Path options is not followed by a path or a file name, output file name will be based on the web extension's directory name.

Private key file will not be created if one already exist. Existing one will be used. CRX, ZIP and XML files are always overwritten.

--appVersion, --crxURL and --browserVersion are used only for writing XML file.

For example:

crx3 -p -o -x -z web-extension

It will create "web-extension.pem" (if one does not exist yet), "web-extension.crx", "web-extension.xml" and "" files.

WARNING: if you're using option without name/path, it must be specified before option with name/path. Otherwise, be sure that the list of directories and/or files to include in web extension file is specified after the special -- marker, like this:

crx3 -z -x -o -- web-extension

If you already have a ZIP file containing web extension's files, you can use CRX3 like this:

cat | crx3 -p web-extension.pem

It will read existing ZIP file contents and create "web-extension.crx" and "web-extension.pem" files. Make sure that ZIP file content has no parent directory, e.g., "manifest.json" file has to be there, not "web-extension/manifest.json". Otherwise new CRX file will not work in a browser.

WARNING: CRX3 does not read contents of the ZIP file. Which means, that for an optional XML file to be working, either APP_VERSION environment variable or --appVersion argument has to be specified. Otherwise XML file will contain "${APP_VERSION}" placeholder instead. Same for CRX_URL/--crxURL and BROWSER_VERSION/--browserVersion values.

You can also create ZIP file on the fly, and pass it like this:

zip -r -9 -j - web-extension | crx3 -p web-extension.pem

Usage (API)

const crx3 = require('crx3');
crx3(['example/example-extension/manifest.json'], {
    keyPath: 'example/example-extension.pem',
    crxPath: 'example/example-extension.crx',
    zipPath: 'example/',
    xmlPath: 'example/example-extension.xml',
    crxURL : ''
    .then(() => console.log('done'))

Known Issues


Since version 75.x, Chrome requires Google's web store signature on extension files. CRX3 module does not provide those (that would require access to Google's private key). Following information is "guessed" by checking Chromium's source code at:

So, there's a chance i got it wrong, in which case do not be afraid to create a new issue about it.

Unless extension is being installed through the chrome://extensions/ page, with "developer mode" enabled beforehand (it has to be enabled and then Chrome has to be restarted), there's a big chance that users will see CRX_REQUIRED_PROOF_MISSING error when they try to install .crx file created with CRX3 module.

If extension is installed manually, on MacOS or Linux, it can be installed as long as:

On Windows, they have to be installed in "developer mode", or through enterprise policy (see

On all systems, extensions can be installed through a policy setup:

API Documentation

To generate documentation for this module, clone module from repository (package does not include required files) and use:

npm run doc

To write extensions, use Extension API for Chrome/Chromium and WebExtensions API for Mozilla browsers. They are quite similar, so it is possible to create an extension that works on all of them (it just needs to be build into different extension file formats - you can use for Mozilla).


To run tests, clone module (see API Documentation) and use:

npm test

Tests include optional support for checking generated CRX file in Chromium browser when run on Linux system. To make it work:

  • make sure that Chrome or Chromium browser is installed,
  • make sure that CHROME_BIN environment variable is set with path to the browser's executable,
  • if they were not available when installing CRX3 module, run npm install again (to install additional dependencies).

WARNING: Since there is no way to imitate installation process of a CRX file through puppeteer (or is there?), test will try to create an /etc/chromium/policies/managed/crx3-example-extension-test.json policy file to "force install" it. That is why it is best to run whole thing in a virtual machine, e.g., using qemu, or in a container, e.g., using podman or docker.

Using podman:

podman run --rm -v $(pwd):/app -v $(pwd)/node_modules:/app/node_modules --userns=keep-id -it ahwayakchih/nodeapp:puppeteer xvfb-run npm test

Using docker:

docker run --rm -v $(pwd):/app -v $(pwd)/node_modules:/app/node_modules -it ahwayakchih/nodeapp:puppeteer xvfb-run npm test

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