System Requirements

Watchman is known to compile and pass its test suite on:

  • Linux systems with inotify
  • macOS (uses FSEvents on 10.7+, kqueue(2) on earlier versions)
  • Windows x64 on Windows 7, Windows Server 2012 R2 and later is currently in beta status.

Watchman used to support the following systems, but no one is actively maintaining them. The core of the code should be OK, but they likely don't build. We'd love it if someone would step forward to maintain them:

  • BSDish systems (FreeBSD 9.1, OpenBSD 5.2) that have the kqueue(2) facility
  • Illumos and Solaris style systems that have port_create(3C)

Watchman relies on the operating system facilities for file notification, which means that you will likely have very poor results using it on any kind of remote or distributed filesystem.

Watchman does not currently support any other operating system not covered by the list above.

Download for Windows (Beta)

Watchman is considered to be in beta status for Windows but has a reasonably sized group of users depending on it already, and we expect to remove the beta label in the coming months.

Watchman was built to support Windows Server 2012 R2 and later, but has had community-provided patches that enable support for Windows 7 and later.

At this time, we recommend running the latest master build of watchman on Windows; see below for binary downloads!

If you encounter issues with the Windows version of watchman, please report them via GitHub! You can find the list of known Windows issues here.

Binary Downloads for Linux, macOS and Windows (Beta)

We use GitHub Actions to build binaries for the following platforms:

  • macOS
  • Ubuntu 18.04
  • Windows

GitHub Actions doesn't provide a way to link directly to these builds at this time, so you will need to follow these steps to download the binaries:

  • Look in the top right of the resulting page for the Artifacts drop down

  • Click it to reveal the download artifacts link
  • Click that and extract the zip file
  • For Windows users:
    • Copy windows\bin directory somewhere and add it to your PATH environment variable.


Installing on macOS or Linux via Homebrew

To build the most recent release currently tracked by Homebrew:

$ brew update
$ brew install watchman

To install the latest build from github:

$ brew install --HEAD watchman

Installing on macOS via macports

To install the package maintained by MacPorts:

$ sudo port install watchman

Installing from source

You can use these steps below to get watchman built. You will need libssl-dev, autoconf, automake and libtool (or glibtool on macOS).

You may optionally build watchman without pcre and python support (see configuration options below).

For python support, you will need setuptools and may need to install a python-dev or python-devel package. To build the C++ client library you will need to install libfolly.

See below for some more information on options to configure your build.

$ # use the latest stable release
$ git clone -b v4.9.0 --depth 1
$ cd watchman
$ ./
$ ./configure
$ make
$ sudo make install

Compile Time Configuration Options

Our configure script accepts all the standard options, but there are a couple that are specific to watchman that might be relevant to your needs:

--enable-conffile=PATH Use PATH as the default configuration file name.
Default is /etc/watchman.json
--enable-statedir=PATH Use PATH as the default for state, log files
and sockets instead of using your system tempdir
--enable-lenient Turn off more pedantic levels of warnings
and compilation checks
--enable-stack-protector Enable stack protection in the same
way that rpmbuild does on some systems.
--enable-cppclient Enable build of the C++ client library. This is built by
default if Folly is available.
--with-buildinfo=TEXT Include some extra build information that will
be reported in the version command output
--without-python Disable python bindings
--with-python=PATH Enable Python bindings. PATH is location of python.
Default is to look for python in your PATH
--without-pcre Don't enable pcre support.
--with-pcre=PATH Enable pcre support. PATH is location of pcre-config.
Default is to enable and look for pcre-config in your
--with-folly=PATH Specify root for Folly (needed for the C++ client library)

(Run ./configure --help to get the list for the version you checked out)

Continuous Integration

We use continuous integration to build out every revision and pull-request to make sure that we don't accidentally break things. The current build status is:

Build Status

Build status

System Specific Preparation

Linux inotify Limits

The inotify(7) subsystem has three important tunings that impact watchman.

  • /proc/sys/fs/inotify/max_user_instances impacts how many different root dirs you can watch.
  • /proc/sys/fs/inotify/max_user_watches impacts how many dirs you can watch across all watched roots.
  • /proc/sys/fs/inotify/max_queued_events impacts how likely it is that your system will experience a notification overflow.

You obviously need to ensure that max_user_instances and max_user_watches are set so that the system is capable of keeping track of your files.

max_queued_events is important to size correctly; if it is too small, the kernel will drop events and watchman won't be able to report on them. Making this value bigger reduces the risk of this happening.

Watchman has two simple strategies for mitigating an overflow of max_queued_events:

  • It uses a dedicated thread to consume kernel events as quickly as possible
  • When the kernel reports an overflow, watchman will assume that all the files have been modified and will re-crawl the directory tree as though it had just started watching the dir.

This means that if an overflow does occur, you won't miss a legitimate change notification, but instead will get spurious notifications for files that haven't actually changed.

Mac OS File Descriptor Limits

Only applicable on macOS 10.6 and earlier

The default per-process descriptor limit on macOS is extremely low (256!).

Watchman will attempt to raise its descriptor limit to match kern.maxfilesperproc when it starts up, so you shouldn't need to mess with ulimit; just raising the sysctl should do the trick.

The following will raise the limits to allow 10 million files total, with 1 million files per process until your next reboot.

$ sudo sysctl -w kern.maxfiles=10485760
$ sudo sysctl -w kern.maxfilesperproc=1048576

Putting the following into a file named /etc/sysctl.conf on macOS will cause these values to persist across reboots: