About 5 years ago Mozilla shipped Firefox Quantum, an upgrade that included significant performance improvements for most Firefox users. Unfortunately, Firefox Quantum didn’t improve performance for people who use screen readers and other assistive technology. In some ways, our screen reader performance actually regressed with the architecture changes that Quantum delivered.
The Firefox accessibility engineers remedied much of that performance regression in the late Twenty-Teens, but by 2020 they’d done all they could to keep up. Continued investment in the old architecture simply wasn’t going to be enough to maintain a competitive browser so we began planning a re-write, which became a project called Cache the World. This upgrade changes the way things work in Firefox’s accessibility code so that screen readers and other assistive technologies have fast access to the content they need.
Today, with the release of Firefox 113, those improvements are available to all Firefox users on Windows, Mac, Linux, and Android.
Browsers are more complicated today than when Firefox’s accessibility engine was first designed, and the most significant overall change has been the move to security-isolated, multi-process architectures. With multiple isolated processes, screen readers had to do a lot of expensive work to retrieve and relay content to users. We were inspired by Chrome’s approach and extended it to improve Firefox’s accessibility performance; Firefox now provides a cache of all tab and browser UI content to screen readers in the browser’s parent process, where it can be used quickly and very easily.
This blog post by accessibility tech lead Jamie Teh provides more context and technical details on the project, but the largest impact you’ll notice immediately is speed. For some of the worst use cases — like pages with very large tables — Firefox now performs up to 20 times faster, and we’re clocking other very large pages at 10 times faster! However, even for the most everyday actions, like opening and closing a Gmail message or switching channels in a Slack window, the performance is 2 to 3 times better.
This upgrade shipped for Android last year in the Firefox 102 release, for Windows and Linux in the Firefox 112 release, and today it arrives on MacOS, which completes our rollout to all Firefox platforms. We’re very excited to be delivering this performance and stability improvement to you all, and we’re eager to hear your feedback and answer questions. Please let us know what you think about these changes in a comment on this post, and if you’ve found something broken, report it in a Bugzilla ticket. Got a completely different idea for making Firefox accessibility better? Please join us on and share via Mozilla Connect.
Asa Dotzler, on behalf of the Firefox accessibility team: Jamie Teh, Eitan Isaacson, Morgan Rae Reschenberg, Anna Yeddi, Nathan LaPré, and Kim Bryant