When add-ons were first introduced as a way to personalize Firefox, they required a restart of Firefox upon installation. Then came “restartless” extensions, which made the experience of installing an add-on much smoother. Every iteration of extensions APIs since then has similarly supported restartless add-ons, up to WebExtensions.
To indicate that an add-on was restartless, we added “No Restart” badges next to them on addons.mozilla.org (AMO). This helped people see which add-ons would be smoother to install, and encouraged developers to implement them for their own add-ons. However, two things happened recently that prompted us to reverse this badge. Now, rather than using a “No Restart” badge to indicate that an add-on is restartless, we will use a “Restart Required” badge to indicate that an add-on requires a restart.
One reason for this change is because we reached a tipping point: now that restartless add-ons are more common, and the number of WebExtensions add-ons is increasing, there are now more extensions that do not require a restart than those that do.
Another reason is that we encountered an unexpected issue with the recent introduction of multiprocess Firefox. In Firefox 48, multiprocess capability was only enabled for people with no add-ons installed. If you are one of these people and you now install an add-on, you’ll be asked to restart Firefox even if the add-on is restartless. This forced restart will only occur over the next few versions as multiprocess Firefox is gradually rolled out. This is not because of the add-on, but because Firefox needs to turn multiprocess off in order to satisfy the temporary rule that only people without add-ons installed have multiprocess Firefox enabled. So a “No Restart” badge may be confusing to people.
Restartless add-ons becoming the norm is a great milestone and a huge improvement in the add-on experience, and one we couldn’t have reached without all our add-on developers—thank you!