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The Servo Browser Engine

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The Servo Parallel Browser Engine Project

Linux Build Status Changelog #228

Servo is a prototype web browser engine written in the Rust language. It is currently developed on 64-bit macOS, 64-bit Linux, 64-bit Windows, and Android.

Servo welcomes contribution from everyone. See
for help getting started.

Visit the Servo Project page for news and guides.

Setting up your environment

Building servo requires rustup, version 1.8.0 or more recent. If you have an older version, run

rustup self update

To install on Windows, download and run

then follow the onscreen instructions.

To install on other systems, run:

curl -sSf | sh

This will also download the current stable version of Rust, which Servo won’t use. To skip that step, run instead:

curl -sSf | sh -s -- --default-toolchain none

See also Other installation methods

Other dependencies

Please select your operating system: * macOS * Debian-based Linuxes * Fedora * Arch Linux * openSUSE * Gentoo Linux * Microsoft Windows * Android


Xcode version 10.2 or above is recommended.

On macOS(Intel based or ARM based) (Homebrew)

NOTE: run these steps after you've cloned the project locally.

cd servo 
brew bundle install --file=etc/taskcluster/macos/Brewfile
brew bundle install --file=etc/taskcluster/macos/Brewfile-build
pip install virtualenv

On Debian-based Linuxes

sudo apt install python3-virtualenv python3-pip
./mach bootstrap


./mach bootstrap
doesn't work, file a bug, and, run the commands below:
sudo apt install git curl autoconf libx11-dev libfreetype6-dev libgl1-mesa-dri \
    libglib2.0-dev xorg-dev gperf g++ build-essential cmake libssl-dev \
    liblzma-dev libxmu6 libxmu-dev \
    libxcb-render0-dev libxcb-shape0-dev libxcb-xfixes0-dev \
    libgles2-mesa-dev libegl1-mesa-dev libdbus-1-dev libharfbuzz-dev ccache \
    clang libunwind-dev libgstreamer1.0-dev libgstreamer-plugins-base1.0-dev \
    libgstreamer-plugins-bad1.0-dev autoconf2.13 llvm-dev

Additionally, you'll need a local copy of GStreamer with a version later than 16.2. You can place it in

, or run
./mach bootstrap-gstreamer
to set it up. On Ubuntu 20.04LTS, you can use the system GStreamer if you install the necessary packages:
sudo apt install gstreamer1.0-nice gstreamer1.0-plugins-bad

If you are using Ubuntu 16.04 or Linux Mint 18.* run

before building to avoid an error with harfbuzz.

If you get an undefined symbol error on

try removing
and all old versions of clang, see #22016

On Fedora

sudo dnf install python3 python3-virtualenv python3-pip python3-devel
python3 ./mach bootstrap


python3 ./mach bootstrap
doesn't work, file a bug, and, run the commands below:
sudo dnf install curl libtool gcc-c++ libXi-devel libunwind-devel \
    freetype-devel mesa-libGL-devel mesa-libEGL-devel glib2-devel libX11-devel \
    libXrandr-devel gperf fontconfig-devel cabextract ttmkfdir  expat-devel \
    rpm-build openssl-devel cmake libX11-devel libXcursor-devel \
    libXmu-devel dbus-devel ncurses-devel harfbuzz-devel \
    ccache clang clang-libs python3-devel gstreamer1-devel \
    gstreamer1-plugins-base-devel gstreamer1-plugins-bad-free-devel autoconf213

On CentOS

sudo yum install python-virtualenv python-pip
./mach bootstrap


./mach bootstrap
doesn't work, file a bug, and, run the commands below:
sudo yum install curl libtool gcc-c++ libXi-devel freetype-devel \
    mesa-libGL-devel mesa-libEGL-devel glib2-devel libX11-devel libXrandr-devel \
    gperf fontconfig-devel cabextract ttmkfdir python expat-devel rpm-build \
    openssl-devel cmake3 libXcursor-devel libXmu-devel \
    dbus-devel ncurses-devel python34 harfbuzz-devel \
    ccache clang clang-libs llvm-toolset-7

Build inside

scl enable devtoolset-7 llvm-toolset-7 bash

with the following environmental variables set:

export CMAKE=cmake3
export LIBCLANG_PATH=/opt/rh/llvm-toolset-7/root/usr/lib64

On openSUSE Linux

sudo zypper install libX11-devel libexpat-devel Mesa-libEGL-devel Mesa-libGL-devel cabextract cmake \
    dbus-1-devel fontconfig-devel freetype-devel gcc-c++ git glib2-devel gperf \
    harfbuzz-devel libXcursor-devel libXi-devel libXmu-devel libXrandr-devel libopenssl-devel \
    python3-pip python3-virtualenv rpm-build ccache llvm-clang libclang autoconf213 gstreamer-devel \
    gstreamer-plugins-base-devel gstreamer-plugins-bad-devel

On Arch Linux

sudo pacman -S --needed base-devel git python python-virtualenv python-pip mesa cmake libxmu \
    pkg-config ttf-fira-sans harfbuzz ccache llvm clang autoconf2.13 gstreamer gstreamer-vaapi \
    gst-plugins-base gst-plugins-good gst-plugins-bad

On Gentoo Linux

sudo emerge net-misc/curl \
    media-libs/freetype media-libs/mesa dev-util/gperf \
    dev-python/virtualenv dev-python/pip dev-libs/openssl \
    media-libs/harfbuzz dev-util/ccache sys-libs/libunwind \
    x11-libs/libXmu x11-base/xorg-server sys-devel/clang \
    media-libs/gstreamer media-libs/gst-plugins-bad media-libs/gst-plugins-base

With the following environment variable set:

export LIBCLANG_PATH=$(llvm-config --prefix)/lib64

On nixOS Linux

nix-shell etc/shell.nix

You will need to run this in every shell before running mach.

On Windows (MSVC)

  1. Install Python 3.9 for Windows ( The Windows x86-64 MSI installer is fine. This is required in order to build the JavaScript engine, SpiderMonkey.

You will also need to set the

environment variable, e.g., to 'C:\Python39\python.exe' by doing:
setx PYTHON3 "C:\Python39\python.exe" /m
will set it system-wide for all future command windows.
  1. Install virtualenv.

In a normal Windows Shell (cmd), do:

pip install virtualenv
If this does not work, you may need to reboot for the changed PATH settings (by the python installer) to take effect.
  1. Install the most recent GStreamer MSVC packages. You need to download the two
    files for your platform from the GStreamer website and install them. The currently recommended version is 1.16.0. i.e.:

Note that the MinGW binaries will not work, so make sure that you install the MSVC ones.

Note that you should ensure that all components are installed from gstreamer, as we require many of the optional libraries that are not installed by default.

  1. Install Git for Windows ( DO allow it to add git.exe to the PATH (default settings for the installer are fine).

  2. Install Visual Studio Build Tools 2019 ( It is easiest to install via Chocolatey with:

    choco install -y visualstudio2019buildtools --package-parameters="--add Microsoft.VisualStudio.Component.Roslyn.Compiler --add Microsoft.Component.MSBuild --add Microsoft.VisualStudio.Component.CoreBuildTools --add Microsoft.VisualStudio.Workload.MSBuildTools --add Microsoft.VisualStudio.Component.Windows10SDK --add Microsoft.VisualStudio.Component.VC.CoreBuildTools --add Microsoft.VisualStudio.Component.VC.Tools.x86.x64 --add Microsoft.VisualStudio.Component.VC.Redist.14.Latest --add Microsoft.VisualStudio.Component.VC.ATL --add Microsoft.VisualStudio.Component.VC.ATLMFC --add Microsoft.VisualStudio.Component.TextTemplating --add Microsoft.VisualStudio.Component.VC.CoreIde --add Microsoft.VisualStudio.ComponentGroup.NativeDesktop.Core --add Microsoft.VisualStudio.Workload.VCTools"
    If you really need to use the Visual Studio Installer (UI), choose "Desktop development with C++" and add the optional "MSVC", "C++-ATL" and "C++-MFC" (latest).

The Visual Studio 2019 Build Tools MUST be installed to the default location or mach.bat will not find them.

[Optional] Install LLVM for faster link times

You may experience much faster builds on Windows by following these steps. (Related Rust issue:

  1. Download the latest version of LLVM (
  2. Run the installer and choose to add LLVM to the system PATH.
  3. Add the following to your Cargo config (Found at
    ). You may need to change the triple to match your environment.
linker = "lld-link.exe"
Troubleshooting a Windows environment

If you have troubles with

x64 type
prompt as
set by default: 1. You may need to choose and launch the type manually, such as
x86_x64 Cross Tools Command Prompt for VS 2019
in the Windows menu.) 2.
cd to/the/path/servo
python mach build -d

If you got the error

Cannot run mach in a path on a case-sensitive file system on Windows
: 1. Open Command Prompt or PowerShell as administrator. 2. Disable case-sensitive for servo path,
fsutil.exe file SetCaseSensitiveInfo X:\path\to\servo disable

If you got the error

DLL file
not found!
then set the
environment variable to an appropriate
Windows Kit
directory containing
, for example
C:\Program Files (x86)\Windows Kits\10

If you get the error

thread 'main' panicked at 'Unable to find libclang: "couldn\'t find any valid shared libraries matching: [\'clang.dll\', \'libclang.dll\'], set the
environment variable to a path where one of these files can be found (invalid: ... invalid DLL (64-bit))])"'
may have installed the 32-bit default target rather than the 64-bit one. You can find the configuration with
rustup show
, and set the default with `rustup set default-host x86

Cross-compilation for Android


./mach bootstrap-android --build
to get Android-specific tools. See wiki for details.

Cloning the Repo

Your CARGO_HOME needs to point to (or be in) the same drive as your Servo repository (See #28530).

git clone
cd servo


Servo is built with Cargo, the Rust package manager. We also use Mozilla's Mach tools to orchestrate the build and other tasks. You can call Mach like this:

On Unix sytems:

./mach [command] [arguments]
On Windows Commandline:
mach.bat [command] [arguments]
The examples below will use Unix, but the same applies to Windows.

The Rust compiler

Servo's build system uses to automatically download a Rust compiler. This is a specific version of Rust Nightly determined by the


Normal build

To build Servo in development mode. This is useful for development, but the resulting binary is very slow:

./mach build --dev
./mach run tests/html/about-mozilla.html

Release build

For benchmarking, performance testing, or real-world use. Add the

flag to create an optimized build:
./mach build --release
./mach run --release tests/html/about-mozilla.html


mach build
will build both
. To make compilation a bit faster, it's possible to only compile the servo binary:
./mach build --dev -p servo

Checking for build errors, without building

If you’re making changes to one crate that cause build errors in another crate, consider this instead of a full build:

./mach check

It will run

cargo check
, which runs the analysis phase of the compiler (and so shows build errors if any) but skips the code generation phase. This can be a lot faster than a full build, though of course it doesn’t produce a binary you can run.

Building for Android target

For ARM (

, most phones):
./mach build --release --android
./mach package --release --android

For x86 (typically for the emulator):

./mach build --release --target i686-linux-android
./mach package --release --target i686-linux-android


Run Servo with the command:

./servo [url] [arguments] # if you run with nightly build
./mach run [url] [arguments] # if you run with mach

For example

./mach run

Commandline Arguments

    turns on the profiler and dumps info to the console every
  • -s SIZE
    sets the tile size for painting; defaults to 512
  • -z
    disables all graphical output; useful for running JS / layout tests
  • -Z help
    displays useful output to debug servo

Keyboard Shortcuts

  • Ctrl
    opens URL prompt (
    on Mac)
  • Ctrl
    reloads current page (
    on Mac)
  • Ctrl
    zooms out (
    on Mac)
  • Ctrl
    zooms in (
    on Mac)
  • Alt
    left arrow
    goes backwards in the history (
    left arrow
    on Mac)
  • Alt
    right arrow
    goes forwards in the history (
    right arrow
    on Mac)
  • Esc
    exits Servo (
    on Mac)


There are lots of mach commands you can use. You can list them with


The generated documentation can be found on

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