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The Servo Browser Engine
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bors-servo Auto merge of #23804 - Manishearth:transform-tests, r=asajeffrey
Improve xrRigidTransform_constructor test

It contained an incorrect test attempting to construct a transform that throws. Added tests that check that it throws appropriately.

has r+ from #23803, created new PR
due to bug in WPT sync

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Latest commit 5788e8c Jul 19, 2019
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.cargo Use lld-link for windows arm64. Jun 7, 2019
.vscode chore(vscode): Add VSCode recommended extensions Jun 19, 2019
components Auto merge of #23368 - gterzian:clean_up_navigation, r=asajeffrey Jul 18, 2019
docs Update hololens doc Jul 5, 2019
etc Remove rustdoc work-around from 43a7501 Jul 17, 2019
ports Get the glwindow test XR device to share a GL context with WebGL Jul 17, 2019
python Auto merge of #23768 - jdm:unbreak-angle, r=asajeffrey Jul 13, 2019
resources Update test API, hook it up to webxr mocking Jul 11, 2019
support Adjust gstreamer plugins for UWP. Jul 12, 2019
tests Auto merge of #23804 - Manishearth:transform-tests, r=asajeffrey Jul 19, 2019
.gitattributes Explicitly declare image files to be binaries in .gitattributes, so a… Jul 5, 2019
.gitignore Hololens port Jul 3, 2019
.hgignore Add .hgignore file Feb 4, 2017
.mailmap Backed out changeset 3232d68da948 for testing Servo backout service Jun 23, 2017
.taskcluster.yml `git show --pretty=%P` sometimes prints a diff. Use `git cat-file` in… May 23, 2019
.travis.yml Move pre-review PR testing from Travis-CI to Taskcluster Jul 1, 2019
CLOBBER Add clobber mechanism May 8, 2017 Rust's code of conduct link was changed Dec 12, 2018
Cargo.lock Auto merge of #23784 - asajeffrey:webxr-glwindow-share-contexts, r=Ma… Jul 18, 2019
Cargo.toml Update webrender. Jul 12, 2019
Info.plist remove bhtml Feb 11, 2018
LICENSE Update MPL license to https (part 1) Nov 19, 2018 Minor pull request template cleanup Dec 8, 2018 Update README about local gstreamer copy path Jul 17, 2019
appveyor.yml Fix Appveyor Jul 12, 2019
dependencyci.yml Don't report smallbitvec as an error. Oct 16, 2017
mach Check for python's version in mach Jun 3, 2019
mach.bat Rework mach.bat to support VS2019 and user-supplied environments. Apr 1, 2019
rust-toolchain Upgrade to rustc 1.38.0-nightly (4b65a86eb 2019-07-15) Jul 17, 2019
rustfmt.toml Reorder imports Nov 6, 2018
servo-tidy.toml Update rayon to dedupe crossbeam-epoch Jul 12, 2019
servobuild.example script: Optionally store backtraces when throwing DOM exceptions. Oct 1, 2018

The Servo Parallel Browser Engine Project

Linux Build Status Windows 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 and 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 rustup-init.exe 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:


Xcode version 10.2 or above is recommended.

On macOS (homebrew)
brew bundle install --file=etc/taskcluster/macos/Brewfile
brew bundle install --file=etc/taskcluster/macos/Brewfile-gstreamer
pip install virtualenv
On macOS (MacPorts)
sudo port install python27 py27-virtualenv cmake yasm llvm
On macOS >= 10.11 (El Capitan), you also have to install OpenSSL
brew install openssl

export OPENSSL_INCLUDE_DIR="$(brew --prefix openssl)/include"
export OPENSSL_LIB_DIR="$(brew --prefix openssl)/lib"

./mach build ...
Note: Please make sure the required PKG_CONFIG_PATH environment variable is set the same as the one provided from brew info libffi (Check this comment for more details).

If you've already partially compiled servo but forgot to do this step, run ./mach clean, set the shell variables, and recompile.

On Debian-based Linuxes

Please run ./mach bootstrap.

If this 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 virtualenv python-pip \
    libssl-dev libbz2-dev liblzma-dev libosmesa6-dev libxmu6 libxmu-dev \
    libglu1-mesa-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

Additionally, you'll need a local copy of GStreamer with a version later than 12.0. You can place it in support/linux/gstreamer/gst, or run ./mach bootstrap-gstreamer to set it up.

If you are using Ubuntu 16.04 or Linux Mint 18.* run export HARFBUZZ_SYS_NO_PKG_CONFIG=1 before building to avoid an error with harfbuzz.

If you get an undefined symbol error on gst_player_get_config try removing gir1.2-gst-plugins-bad-1.0 and all old versions of clang, see #22016

If you are on Ubuntu 14.04 and encountered errors on installing these dependencies involving libcheese, see #6158 for a workaround. You may also need to install gcc 4.9, clang 4.0, and cmake 3.2:

gcc 4.9:
sudo add-apt-repository ppa:ubuntu-toolchain-r/test
sudo apt-get update
sudo apt-get install gcc-4.9 g++-4.9
sudo update-alternatives --install /usr/bin/gcc gcc /usr/bin/gcc-4.9 60 --slave /usr/bin/g++ g++ /usr/bin/g++-4.9

clang 4.0:

wget -O - | sudo apt-key add -
sudo apt-add-repository "deb llvm-toolchain-trusty-4.0 main"
sudo apt-get update
sudo apt-get install -y clang-4.0

cmake 3.2:

sudo apt-get install software-properties-common
sudo add-apt-repository ppa:george-edison55/cmake-3.x
sudo apt-get update
sudo apt-get install cmake

If virtualenv does not exist, try python-virtualenv.

On Fedora

Please run ./mach bootstrap.

If this 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 python2 python2-virtualenv python2-pip expat-devel \
    rpm-build openssl-devel cmake bzip2-devel libX11-devel libXcursor-devel libXmu-devel mesa-libOSMesa-devel \
    dbus-devel ncurses-devel harfbuzz-devel ccache mesa-libGLU-devel clang clang-libs gstreamer1-devel \
    gstreamer1-plugins-base-devel gstreamer1-plugins-bad-free-devel autoconf213

On CentOS

Please run ./mach bootstrap.

If this 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 python-virtualenv python-pip expat-devel \
    rpm-build openssl-devel cmake3 bzip2-devel libXcursor-devel libXmu-devel mesa-libOSMesa-devel \
    dbus-devel ncurses-devel python34 harfbuzz-devel ccache clang clang-libs llvm-toolset-7

Build inside llvm-toolset and devtoolset:

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 libbz2-devel Mesa-libEGL-devel Mesa-libGL-devel cabextract cmake \
    dbus-1-devel fontconfig-devel freetype-devel gcc-c++ git glib2-devel gperf \
    harfbuzz-devel libOSMesa-devel libXcursor-devel libXi-devel libXmu-devel libXrandr-devel libopenssl-devel \
    python-pip python-virtualenv rpm-build glu-devel 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 python2 python2-virtualenv python2-pip mesa cmake bzip2 libxmu glu \
    pkg-config ttf-fira-sans harfbuzz ccache clang autoconf2.13 gstreamer gstreamer-vaapi

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 media-libs/glu 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 Windows (MSVC)

  1. Install Python for Windows ( The Windows x86-64 MSI installer is fine. You should change the installation to install the "Add python.exe to Path" feature.

  2. Install virtualenv.

In a normal Windows Shell (cmd.exe or "Command Prompt" from the start menu), 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 development package following these instructions. You will also need to add C:\gstreamer\1.0\x86_64\lib to your LIB environment variable.

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

  3. Install Visual Studio Community 2017 ( You MUST add "Visual C++" to the list of installed components. It is not on by default. Visual Studio 2017 MUST installed to the default location or mach.bat will not find it.

[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 %USERPROFILE%\.cargo\config). You may need to change the triple to match your environment.
linker = "lld-link.exe"
Troubleshooting a Windows environment

If you encountered errors with the environment above, do the following for a workaround:

  1. Download and install Build Tools for Visual Studio 2017
  2. Install python2.7 x86-x64 and virtualenv
  3. Run mach.bat build -d.

If you have troubles with x64 type prompt as mach.bat set by default:

  1. You may need to choose and launch the type manually, such as x86_x64 Cross Tools Command Prompt for VS 2017 in the Windows menu.)
  2. cd to/the/path/servo
  3. 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

Cross-compilation for Android

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

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 rust-toolchain file.


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

Normal build

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

git clone
cd servo
./mach build --dev
./mach run tests/html/about-mozilla.html

Or on Windows MSVC, in a normal Command Prompt (cmd.exe):

git clone
cd servo
mach.bat build --dev

For benchmarking, performance testing, or real-world use, add the --release flag to create an optimized build:

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

Note: mach build will build both servo and libsimpleservo. 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 (armv7-linux-androideabi, 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

  • -p INTERVAL turns on the profiler and dumps info to the console every INTERVAL seconds
  • -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+L opens URL prompt (Cmd+L on Mac)
  • Ctrl+R reloads current page (Cmd+R on Mac)
  • Ctrl+- zooms out (Cmd+- on Mac)
  • Ctrl+= zooms in (Cmd+= on Mac)
  • Alt+left arrow goes backwards in the history (Cmd+left arrow on Mac)
  • Alt+right arrow goes forwards in the history (Cmd+right arrow on Mac)
  • Esc or Ctrl+Q exits Servo (Cmd+Q on Mac)


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

The generated documentation can be found on

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