Firefox and Gecko's roots go back to the Netscape codebase, which already supported the Mac as it was in 1994. Although continuously updated, Firefox still uses a wide range of macOS APIs that followed the Mac's evolution over the years (Carbon, Cocoa, HITheme, Quartz, ...). Apple has generally kept them - the code is there and working, after all - and has even added compatibility shims in some places where behavior has changed.

From the perspective of Mozilla's platform team, an area of particular interest for such an architecture change on macOS is Firefox's use of macOS APIs. While the claim initially met some skepticism, near the end of 2018, computer hardware magazine AnandTech published the results of running the industry-standard SPEC benchmark on the iPhone XS, showing that even workloads that reflect real-world desktop use cases reached desktop chip performance, and were doing so at significantly better power efficiency.

As early as 2013, Apple had referred to the custom ARM chips they were putting in the iPhone as 'desktop-class' designs. Speculation that Apple would switch its Mac lineup to use ARM CPUs had been ongoing in the industry for several years. With the release of Apple Silicon-based Macs at the end of last year, generated a flurry of news coverage and some surprises at the machine's performance.

In this article, we'll take you through the background information on the experience of porting Firefox to run natively on these CPUs. We'll start with some background on the Mac transition and give an overview of Firefox internals that needed to know about the new architecture, before moving on to the concept of Universal Binaries. We'll then explain how DRM/EME works on the new platform, talk about our experience with macOS Big Sur, and discuss various updater problems we had to deal with.

Overall, the transition to ARM CPUs for Macs is an exciting development that has presented both challenges and opportunities for Firefox and Gecko. In this article, we'll delve into the details of how we've approached this transition and what it means for our users.

Firefox mac m1