Mozilla begins crackdown on slow starting Firefox add-ons

Mozilla has announced that it is going to be more hands-on with add-on performance. According to Mozilla's Justin Scott, Product Manager for Add-Ons, the average add-on increases start-up time by about 10%; the actual impact in seconds depends upon the user's hardware and software. Scott says in his announcement that the company estimates that installing ten add-ons typically doubles Firefox's startup time. With this in mind, Mozilla is planning a range of initiatives to take on the bad performers.

One of the changes will also improve the browser's integrity and security: an upcoming version of Firefox will not install third party add-ons unless the user has explicitly given permission for them to be installed. Scott says this change is being made because the silent installation of add-ons by third party software such as toolbars or other frameworks degrades Firefox performance without the user knowing why. The technique can also be used to install add-ons which compromise a user's security, so the planned change will inform users of what is being installed and allow them to block installation if they do not recognise the add-on.

To evaluate start-up performance, automated performance testing is being run on the top 100 add-ons in the Mozilla add-ons gallery; the worst offenders are already displayed online. Mozilla is going to expand this effort to all new versions of add-ons and add new test metrics such as measuring the effect on page load time. In the next two weeks, any add-on that increases startup time by more than 25% will be flagged in the Add-Ons gallery and the browser's add-ons manager.

Mozilla is contacting the developers of the worst performing add-ons to encourage them to improve their performance and has updated the guidance in its Performance best practices document. Over the next few months, Mozilla will also bring on-demand performance testing online for developers to let them see how effective their performance fixes are. Mozilla says that developers should be aiming for a "5% start-up impact or less" and remind users that the best way to combat slow add-ons is by disabling the ones that are not being actively used.

(djwm)