10 Sep 2026

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Jonathan Almeida: Move MOZ_OBJDIR outside of mozilla-central to speed up your IDE

In mozilla-central (the firefox monorepo), a default object store directory is created within the source directory. This is equivalent to the build/ directory you would typically see in other projects.

While this is typically fine, I've found that Android Studio indexes these files and we don't (yet?) have the ability to inform it to not do so because an objdir needs to be evaluated from MOZ_OBJDIR first.

Over time, I ended up with these build directories that grew over time:

Directory Last touched Size Files
obj-aarch64-unknown-linux-android 2025-11-04 29 G 113,116
objdir-desktop 2025-11-04 19 G 41,010
objdir-frontend 2026-09-09 6.3 G 66,930
obj-aarch64-apple-darwin24.5.0 2025-06-16 4 K 1

That's a lot to index! A way around this problem is to move the objdir out of the source directory and into something like ~/.mozbuild:

mk_add_options MOZ_OBJDIR="$HOME/.mozbuild/objdirs/$(basename `pwd`)/objdir-frontend"

Why make this so complicated?

  1. I use workspaces, so each of those have their own project directory with a different name - I've only gone one level down, but you could try everything from $HOME upward.
  2. You can have multiple objdirs for various build types depending on what you're working on.
  3. On most build machines, the .mozbuild directory is fairly optimized to be a fast accessor on the filesystem; close to the rest of the build files.

Given the above, this is what my final mozconfig looks like:

# Build GeckoView/Firefox for Android:
ac_add_options --enable-application=mobile/android

# Targeting the following architecture.
# For regular phones, no --target is needed.
# For x86 emulators (and x86 devices, which are uncommon):
# ac_add_options --target=i686
# For newer phones or Apple silicon
ac_add_options --target=aarch64
# For x86_64 emulators (and x86_64 devices, which are even less common):
# ac_add_options --target=x86_64

# sccache will significantly speed up your builds by caching
# compilation results. The Firefox build system will download
# sccache automatically.
# This only works for non-artifact builds.
#ac_add_options --with-ccache=sccache

# Enable artifact builds.
ac_add_options --enable-artifact-builds

# Write build artifacts to..
BASE_OBJDIR="$HOME/.mozbuild/objdirs/$(basename `pwd`)"

## Full build dir
#mk_add_options MOZ_OBJDIR="$BASE_OBJDIR/objdir-droid"
#mk_add_options MOZ_OBJDIR="$BASE_OBJDIR/objdir-desktop"

## manager-mode; artifact builds
mk_add_options MOZ_OBJDIR="$BASE_OBJDIR/objdir-frontend"

# Auto-clobber; don't ask
mk_add_options AUTOCLOBBER=1

10 Sep 2026 10:57pm GMT

About:Community: Game on: Play, share, and help shape Mozilla

P.S. Apologies for the delay in publishing this edition on the community blog. The original newsletter was sent to subscribers on August 27.

Firefox was leveling up in August! GeForce NOW arrived on Firefox for Windows, JPEG XL support was on the way, and the Firefox + NVIDIA teams joined forces for a Reddit AMA. We also invited SUMO and Mozilla Connect contributors to share their experiences through the Mozilla Contributor Survey, which has since closed (thank you to everyone who took the time to participate!).

Read on to catch up on what you may have missed and see what the community was up to!

GeForce NOW is now available on Firefox for Windows

Firefox has joined NVIDIA GeForce NOW's supported browser lineup, making it possible to stream more than 2,000 PC games directly from Firefox on Windows. There are no downloads, installs, or hardware upgrades required! Just a Windows PC, a GeForce NOW account, and your existing game library.

Learn more

Share your voice in the Mozilla Contributor Survey 2026

We're gathering feedback from SUMO and Mozilla Connect contributors to help shape the future of Mozilla's contributor community. The 2026 Contributor Survey explores what motivates you to contribute, what matters most throughout your contributor journey, and how we can improve areas such as onboarding, recognition, and the upcoming Mozilla Connect migration to SUMO. The survey takes about 10 minutes to complete and is now open until September 1, 2026, end of day UTC.

Complete the survey

JPEG XL is coming to Firefox

Firefox plans to ship support for JPEG XL, a modern image format designed to deliver high-quality images more efficiently. With progressive rendering, images can start appearing before they have fully downloaded so it helps make pages feel faster, especially on slower connections.

Learn more

From the Reddit Community

The Firefox and NVIDIA GeForce NOW teams are hosting a Reddit AMA on September 2 to celebrate GeForce NOW support on Firefox for Windows. Bring your questions about the integration, share your cloud-gaming setup, and let the teams know what else you'd love Firefox to support for online play.

Join the AMA

P.S.

Enjoyed these updates? Subscribe to the Mozilla Community Newsletter and get the latest updates delivered straight to your inbox.

10 Sep 2026 3:05pm GMT

Firefox Tooling Announcements: Happy BMO Push Day! (20260908.1)

Github Link

The following changes have been pushed to bugzilla.mozilla.org:

Discuss these changes in the BMO Matrix Room

1 post - 1 participant

Read full topic

10 Sep 2026 2:34am GMT