#servo #arc #browser #thin


A fork of std::sync::Arc with some extra functionality and without weak references

4 releases (2 breaking)

Uses old Rust 2015

0.3.0 Jun 21, 2023
0.2.0 Feb 20, 2023
0.1.1 Feb 22, 2018
0.1.0 Jan 12, 2018

#57 in Rust patterns

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316,910 downloads per month
Used in 675 crates (3 directly)


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The Servo Parallel Browser Engine Project

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 CONTRIBUTING.md and HACKING_QUICKSTART.md for help getting started.

Visit the Servo Project page for news and guides.

Build Setup

If these instructions fail or you would like to install dependencies manually, try the manual build setup.


  • Install Xcode
  • Install Homebrew
  • Run curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh
  • Run pip3 install virtualenv
  • Run ./mach bootstrap
    Note: This will install the recommended version of GStreamer globally on your system.


  • Run curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh
  • Install Python and virtualenv
    • Debian-like: Run sudo apt install python3-virtualenv python3-pip
    • Fedora: Run sudo dnf install python3 python3-virtualenv python3-pip python3-devel
    • Arch: Run sudo pacman -S --needed python python-virtualenv python-pip
    • Gentoo: Run sudo emerge dev-python/virtualenv dev-python/pip
  • Run ./mach bootstrap


  • Download and run rustup-init.exe then follow the onscreen instructions.
  • Install chocolatey
  • Run mach bootstrap
  • This will install CMake, Git, Ninja, Python and the Visual Studio 2019 Build Tools via choco in an Administrator console. It can take quite a while.
  • If you already have Visual Studio 2019 installed, this may not install all necessary components. Please follow the Visual Studio 2019 installation instructions in the manual setup.
  • Run refreshenv

See also Windows Troubleshooting Tips.

Cloning the Repo

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

git clone https://github.com/servo/servo
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 systems:

./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 rustup.rs to automatically download a Rust compiler. This is a specific version of Rust Nightly determined by the rust-toolchain file.

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 --release flag to create an optimized build:

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

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 https://www.google.com

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)

Runtime dependencies


  • GStreamer >=1.16
  • gst-plugins-bad >=1.16
  • libXcursor
  • libXrandr
  • libXi
  • libxkbcommon
  • vulkan-loader


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

The generated documentation can be found on https://doc.servo.org/servo/index.html


Fork of Arc for Servo. This has the following advantages over std::sync::Arc:

  • We don't waste storage on the weak reference count.
  • We don't do extra RMU operations to handle the possibility of weak references.
  • We can experiment with arena allocation (todo).
  • We can add methods to support our custom use cases 1.
  • We have support for dynamically-sized types (see from_header_and_iter).
  • We have support for thin arcs to unsized types (see ThinArc).
  • We have support for references to static data, which don't do any refcounting.