Firefox now has artifact builds, so if you're not contributing to the C++ portions (the UI or whatever) it will just download build artifacts for you. If you d

Firefox now has artifact builds, so if you're not contributing to the C++ portions (the UI or whatever) it will just download build artifacts for you. If you do want to tweak the native code it should just be ./mach boostrap + ./mach build, but it's entirely possible you'll have trouble with that.