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Write an extension once; have it run on Firefox 3.6, 4, Chrome, Safari and Opera
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Installing Omnium for the first time

Make sure you have NodeJS 0.6+ installed (by running node -v).

Clone omnium:

git clone --recursive

Inside your new omnium folder, install the dependencies:

npm install

Make sure has the right permission:

chmod u+x

Creating an add-on

Steps to create a cross browser plugin:

  1. Create a new project folder. ./
  2. Fill out the build.json file.
  3. Add .js and .css files to /includes/ (Note: if you need them to be loaded in a particular order, use load_order in build.json)
  4. Run the build command from the main directory. ./builder.js [project name]

Right now it's fragile and a lot won't work- this is only v0.1.

Currently only supports Greasemonkey (Fx3.6) and Jetpack (Fx4+). Chrome support coming soon.

For a good example using all of the features, see gkoberger/bugzillajs.


This is woefully underdocumented, so post absolutely any questions in Issues and we'll answer them :)

Or, email us:

  • gkoberger [at] gmail [dot] com
  • mdeboer [at] mozilla [dot] com


  • Make sure you have NodeJS 0.6+ installed (available from various package managers or
  • Run npm install after you've cloned omnium
  • Make sure has the proper permissions (chmod u+x
  • Probably only works in OSX right now
  • Make sure you init and update the submodules
  • Jetpack .xpi's will only run in Fx4+; 3.6 requires Greasemonkey
  • A majority of errors will be because of weird jetpack stuff; try running the jetpack stuff inside .builder/jetpack-sdk manually. Eventually most of these problems will go away.
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