This is a command line tool to help build, run, and test
Ultimately, it aims to support web extensions in a standard, portable,
cross-platform way. Initially, it will provide a streamlined experience for developing
Firefox web extensions.
Installation from npm
npm install --global web-ext
Installation from source
- Node.js, 6.0.0 or higher
- npm, 3.0.0 or higher is recommended
Optionally, you may like:
- nvm, which helps manage node versions
If you had already installed
web-ext from npm,
you may need to uninstall it first:
npm uninstall --global web-ext
Change into the source and install all dependencies:
git clone https://github.com/mozilla/web-ext.git
Build the command:
npm run build
Link it to your node installation:
You can now run it from any directory:
To get updates, just pull changes and rebuild the executable. You don't
need to relink it.
npm run build
Should I Use It?
The web-ext tool enables you to build and ship web extensions for Firefox.
This platform stabilized in
but you may need to develop with a
nightly build of Firefox for some newer web-ext
features. If you are looking to ship an add-on that runs in older versions of
Firefox, consider jpm.
Hi! This tool is under active development. To get involved you can watch the repo,
file issues, create pull requests, or ask a question on
Read the contributing section for how to develop new features.
Some Questions and Answers
Why do we need a command line tool?
This is a great question and one that we will ask ourselves for each new web-ext
feature. Most web extension functionality is baked into the browsers
themselves but a complimentary command line tool will still be helpful.
Here is a partial list of examples:
- File watching.
- When you edit a file, you may need to trigger certain commands (tests,
- Integrating with services.
- Mozilla offers some useful services such as
Why not patch jpm for web extension support?
First, note that jpm is still
actively maintained by Mozilla right now.
We decided not to patch jpm for web extension support (See
jpm issue 445,
Mozilla built cfx
then deprecated it for jpm and now we're proposing a new tool.
I know this is frustrating for developers but web extensions mark a major
turning point. It would be an arduous task to wedge its feature set and
simplified development process into jpm.
Pros of creating a new tool:
- By creating a new tool that focuses on the [emerging] web extension standard,
we have a better chance of interoperating with other platforms, such as
Google Chrome or
It would be hard to do that while preserving compatibility in jpm.
- Creating SDK-based add-ons was overly complicated. With web extensions you no
longer need to convert your source into legacy artifacts and you won't need
- There are superior features in Firefox now for developing extensions such
from source code instead of a packaged XPI. It will be
easier to reimagine a new tool around these work flows rather than
adjust jpm's existing work flows.
- jpm's functional tests are slow, brittle and hard to run. There are flaky
time-outs and we've run out of low hanging fruit fixes at this point.
- Most of jpm's code was not designed to be unit testable which makes it hard to
maintain and refactor.
- jpm's code was written in ES5 which is cumbersome after coming from the ES6
Firefox code base or from most other languages with modern conveniences
(Python, Ruby, etc).
- Some core functionality of jpm can be extracted and re-used in the new tool.
Cons of creating a new tool:
- Firefox extension developers will have to interrupt and re-arrange their work flows.
- Developers of existing add-ons will need to port to web extensions sooner rather than later.
- The web-ext tool will require some ramp-up time for scaffolding.
- The community of jpm contributors will need to shift focus to web-ext.