Mozilla Explains the Reason for Releasing Experimental New Features as Add-ons

Mozilla doesn’t necessarily follow a conventional development cycle, either compared to other open-source outfits or to commercial ones. That’s neither good or bad thing, its approach has both advantages and disadvantages, but there is one trend that seems particularly popular.

In recent years, Mozilla has been testing new features and technologies as add-ons. Experimental programs, the specialty of Mozilla Labs, are released as add-ons, ensuring that a large enough number of people has the possibility to test them, while also not interfering with the development of regular features.

One example that Mozilla is highlighting, is the new Quick Filter feature introduced in Thunderbird 3.1. It’s a handy feature enabling users to quickly sift through large amounts of email. But the interesting thing about it was how it was developed. It started out life as an add-on which Thunderbird 3 users could install.

This had two main advantages. On the one hand, it enabled developers to focus entirely on the feature itself and not have to worry about the state of the other components. On the other hand, it provided them with much more accurate feedback from users that would actually be interested in the feature. No one would install an add-on if they didn’t plan on using it.

Normally, new features are tested in development releases, in Mozilla’s case in nightly builds. But this wasn’t the best approach for all features, especially for user interface ones. “People using Thunderbird nightlies aren’t always interested in that specific feature, so any raw intermediate state makes their daily email experience less pleasant,” Mozilla explains.

“Second, there’s no commonly known mechanism for feedback on a specific feature, so while we may have many users, they often don’t know how to do anything except “file a bug”, which is great for bugs, but not great for user experience feedback; finally, we can only get feedback from people who are brave enough to try out builds that are not tested, which is a very non-representative population sample!,” the entry continues.

The Quick Filter feature is just an example; there are countless others at Mozilla. In fact, many of the projects in Mozilla Labs have either graduated and have been incorporated into the main build, or are on their way of doing so. Personas, the light-weight theme engine is one example of an experimental add-on that was later rolled into Firefox 3.6. The Jetpack SDK, the upcoming add-ons platform for Firefox and Thunderbird is itself released as an add-on until it is ready to be included in the main releases.