Linux build preparation

 The Quickstart Guide

They aren’t complicated, but there are a few prerequisites to building Firefox on Linux. You need:

  • A 64-bit installation of Linux. You can check by opening a terminal window; if uname -m returns x86_64 you can proceed.
  • Next, you’ll need Python 2.7 installed, Python 3.x is currently not supported. You can check with python --version to see if you have it already. If not, you can install it with your distribution’s package manager. Make sure your system is up to date!
  • Finally, a reasonably fast internet connection and 30GB of free disk space.

Getting Started.

Getting set up on Linux is fast and easy.

If you don’t have one yet, create a "src" directory for yourself under your home directory:

mkdir src && cd src

Next download the script and save it in the src/ directory created above.

Building Firefox in Linux on top of a non-native file system - for example, on a mounted NTFS partition - is explicitly not supported. While a build environment like this may succeed it may also fail while claiming to have succeeded, which can be quite difficult to diagnose and fix.

And finally, in your terminal from above start the bootstrapper like this:


... and follow the prompts. This will use mercurial to checkout the source code. If you prefer to work with git, use this command instead:

python --vcs=git

Getting Access

Bugzilla is Mozilla’s issue tracker; you'll need to be able to log into it to comment on a bug or submit a patch.  You can either use your GitHub account, or you can sign up for a Bugzilla account here.

As well as Bugzilla, much of Mozilla’s internal communication happens over IRC. You can download Limechat here for mac, HexChat here for Windows and Linux and learn how to connect to Mozilla with IRC here. If you’re just getting started or have questions about getting set up you can join us in the #introduction channel, where some of our community members hang out to try and help new contributors get rolling.

Get The Code

If you haven't let download mozilla-unified, you can clone mozilla-central repository with the following command, in your terminal:

hg clone

this could take some time depending on your network connection and environment.

If you have any network connection issues and cannot clone with the above command, try Mercurial Bundle.

If Git is your preferred source control management system, follow the instructions at Mozilla: A git workflow for Gecko development instead, to set up a Git repository with git-cinnabar.

Let’s Build Firefox

You’re ready; now we can tie it all together. In your terminal:

cd mozilla-central

If you are not working on the C/C++ files you can also opt for Artifact Builds which are much faster. To enable artifact build set up a .mozconfig file with the following options:

# Automatically download and use compiled C++ components:
# This option will disable C/C++ compilation
ac_add_options --enable-artifact-builds

# Write build artifacts to (not mandatory):
mk_add_options MOZ_OBJDIR=./objdir-frontend

If you plan to walk through code with a debugger, set up a .mozconfig file with the following options:

ac_add_options --disable-optimize
ac_add_options --enable-debug

And finally, run the build command:

./mach build

If you encounter any error related to LLVM/Clang on Ubuntu or Debian, download the latest version of LLVM and Clang and then re-run ./mach build.

And you’re on your way, building your own copy of Firefox from source. Don’t be discouraged if this takes a while; this takes some time on even the fastest modern machines, and as much as two hours or more on older hardware. When the --enable-artifact-builds option is used, builds usually finish within a few minutes.


There’s one more thing you can do for yourself while you’re waiting: create an account for yourself on Mozillians. Mozillians is the Mozilla community directory, where you can connect with people who share your interests, projects or countries. This step is optional, but we think it will be worth your while.

Now the fun starts.

You have the code, you’ve compiled Firefox. Fire it up with ./mach run and you’re ready to start hacking. The next steps are up to you: join us on IRC in the #introduction channel, follow StartMozilla on Twitter and find a bug to start working on.

Detailed Requirements

General considerations

  • 2GB RAM with an additional 2GB of available swap space is the bare minimum, and more RAM is always better - having 8GB or more will dramatically improve build time.
  • 30 GB free disk space.
  • A 64-bit x86 CPU and a 64-bit OS. As of early 2015 it is no longer possible to do a full build of Firefox from source on most 32-bit systems; a 64-bit OS is required. "Artifact builds" may be possible, but are not a supported configuration. On Linux you can determine this by typing "uname -a" in a terminal.
  • A recent version of Clang is required to build Firefox. You can learn more about the features we use and their compiler support here
  • autoconf 2.13. Most Linux distros now install a later version of autoconf, which the build system cannot use, reporting the error "*** Couldn't find autoconf 2.13.  Stop." However a separate autoconf2.13 package is usually available. To install autoconf 2.13 in Debian based distros copy this line and paste it into a terminal window:
sudo apt install autoconf2.13
  • If you are on a Fedora machine then simply install the following prerequisites from the terminal window:
sudo dnf install @development-tools @c-development autoconf213 gtk2-devel gtk3-devel libXt-devel GConf2-devel dbus-glib-devel yasm-devel alsa-lib-devel pulseaudio-libs-devel 

Requirements for Debian / Ubuntu users

You need a number of different packages:

# the rust compiler
aptitude install rustc

# the rust package manager
aptitude install cargo

# the required (old) version of autoconf
aptitude install autoconf2.13

# the headers of important libs
aptitude install libgtk-2-dev
aptitude install libgtk-3-dev
aptitude install libgconf2-dev
aptitude install libdbus-glib-1-dev
aptitude install libpulse-dev

# rust dependencies
cargo install cbindgen

# an assembler for compiling webm
aptitude install yasm 

One-Line Bootstrapping

Our system bootstrapping script can automatically install the required dependencies. You can download and run it by copying this line and pasting it into a terminal window:

wget -q -O && python

Note: piping to stdin of a python process will cause interactive prompts in the bootstrap script to fail, causing the bootstrap process to fail. You must run Python against a local file.

If the above command fails, the reason is often because some Linux distributions ship with an outdated list of root certificates. In this case, you should upgrade your Linux distribution or use your browser to download the file. That ensures that you will get it from the right source.

If you get an error from this process, consider filing a bug saying that the bootstrapper didn't work and contact Mike Hoye directly for help. Please include the error message and some details about your operating system.

If you have already checked out the source code via Mercurial or Git you can also use mach with the bootstrap command:

./mach bootstrap

Common Bootstrapper Failures

wget: command not found

You may not have wget (or curl) installed. In that case, you can either install it via your package manager: 

On Debian-based distros like Ubuntu:

sudo apt install wget 

On Fedora-based distros:

sudo dnf install wget

or you can just download using your browser and then run it with this command:


In some cases people who've customized their command prompt to include emoji or other non-text symbols have found that fails with a UnicodeDecodeError. We have a bug filed for that but in the meantime if you run into this problem you'll need to change your prompt back to something boring.

More info

The above bootstrap script supports popular Linux distributions. If it doesn't work for you, see Linux build prerequisites for more. Again, if you run into other problems or our documentation isn't clear, please contact Mike Hoye directly.