cmd.version.markdown

id	title	layout	category	permalink
cmd.version	version	docs	Commands	docs/cmd/version.html

The version command will tell you the version and build information for the currently running watchman service:

$ watchman version
{
    "version": "2.9.6",
    "buildinfo": "git:2727d9a1e47a4a2229c65cbb2f0c7656cbd96270"
}

To get the version of the client:

$ watchman -v
2.9.8

If the server and client versions don't match up, you should probably restart your server: watchman shutdown-server ; watchman.