Monthly Archives: July 2014

Testing Add-on Compatibility With Multi-Process Firefox

“Electrolysis” (or “e10s” for short) is the project name for Mozilla’s multi-process Firefox. Sandboxing tabs into multiple processes will improve security and UI responsiveness. Firefox currently sandboxes plugins like Flash into a separate process, but sandboxing web content is more difficult because Firefox’s third-party add-ons were not designed for multiple processes. IE and Chrome use multiple processes today, but Google didn’t need to worry about add-on compatibility when designing Chrome’s multi-process sandbox because they didn’t have any. :)

And that’s where our Firefox Nightly testers come in! We can’t test every Firefox add-on ourselves. We’re asking for your help testing your favorite add-ons in Firefox Nightly’s multi-process mode. We’re tracking tested add-ons, those that work and those that need to be fixed, on the website (“Are We e10s Yet?”). Mozilla is hosting a QMO Testday on Friday August 1 where Mozilla QA and e10s developers will be available in Mozilla’s #testday IRC channel to answer questions.

To test an add-on:

  1. Install Firefox Nightly.
  2. Optional but recommended: create a new Firefox profile so you are testing the add-on without any other add-ons or old settings.
  3. Install the add-on you would like to test. See for some suggestions.
  4. e10s is disabled by default. Confirm that the add-on works as expected in Firefox Nightly before enabling e10s. You might find Firefox Nightly bugs that are not e10s’ fault. :)
  5. Now enable e10s by opening the about:config page and changing the browser.tabs.remote.autostart preference to true.
  6. Restart Firefox Nightly. When e10s is enabled, Firefox’s tab titles will be underlined. Tabs for special pages, like your home page or the new tab page, are not underlined, but tabs for most websites should be underlined.
  7. Confirm that the add-on still works as expected with e10s.
  8. To disable e10s, reset the browser.tabs.remote.autostart preference to false and restart Firefox.

Some e10s problems you might find include Firefox crashing or hanging. Add-ons that modify web page content, like Greasemonkey or AdBlock Plus, might appear to do nothing. But many add-ons will just work.

If the add-on works as expected, click the “it works” link on for that add-on or just email me so we can update our list of compatible add-ons.

If the add-on does not work as expected, click the add-on’s “Report bug” link on to file a bug report on Bugzilla. Please include the add-on’s name and version, steps to reproduce the problem, a description of what you expected to happen, and what actually happened. If Firefox crashed, include the most recent crash report IDs from about:crashes. If Firefox didn’t crash, copying the log messages from Firefox’s Browser Console (Tools menu > Web Developer menu > Browser Console menu item; not Web Console) to the bug might include useful debugging information.