# How to Create and Maintain a Tap

[Taps](Taps.md) are external sources of Homebrew formulae, casks and/or external commands. They can be created by anyone to provide their own formulae, casks and/or external commands to any Homebrew user.

## Creating a tap

A tap is usually a Git repository available online, but you can use anything as long as it’s a protocol that Git understands, or even just a directory with files in it. If hosted on GitHub, we recommend that the repository’s name start with `homebrew-` so the short `brew tap` command can be used. See the [`brew` manual page](Manpage.md) for more information on repository naming.

The `brew tap-new` command can be used to create a new tap along with some template files.

Tap formulae follow the same format as the core’s ones, and can be added under either the `Formula` subdirectory, the `HomebrewFormula` subdirectory or the repository’s root. The first available directory is used, other locations will be ignored. We recommend the use of subdirectories because it makes the repository organisation easier to grasp, and top-level files are not mixed with formulae.

See [homebrew/core](https://github.com/Homebrew/homebrew-core) for an example of a tap with a `Formula` subdirectory.

### Naming your formulae to avoid clashes

If a formula in your tap has the same name as a Homebrew/homebrew-core formula they cannot be installed side-by-side. If you wish to create a different version of a formula that's in Homebrew/homebrew-core (e.g. with `option`s) consider giving it a different name; e.g. `nginx-full` for a more full-featured `nginx` formula. This will allow both `nginx` and `nginx-full` to be installed at the same time (assuming one is [`keg_only`](https://rubydoc.brew.sh/Formula#keg_only-class_method) or the linked files do not clash).

## Installing

If it’s on GitHub, users can install any of your formulae with `brew install user/repo/formula`. Homebrew will automatically add your `github.com/user/homebrew-repository` tap before installing the formula. `user/repo/formula` points to the `github.com/user/homebrew-repo/**/formula.rb` file here.

To install your tap without installing any formula at the same time, users can add it with the [`brew tap` command](Taps.md). If it’s on GitHub, they can use `brew tap user/repository`, where `user` is your GitHub username and `homebrew-repository` is your repository. If it’s hosted outside of GitHub, they have to use `brew tap user/repo <URL>`, where `user` and `repository` will be used to refer to your tap and `<URL>` is your Git clone URL.

Users can then install your formulae either with `brew install foo` if there’s no core formula with the same name, or with `brew install user/repo/foo` to avoid conflicts.

## Maintaining a tap

A tap is just a Git repository so you don’t have to do anything specific when making modifications, apart from committing and pushing your changes.

### Updating

Once your tap is installed, Homebrew will update it each time a user runs `brew update`. Outdated formulae will be upgraded when a user runs `brew upgrade`, like core formulae.

## Casks

Casks can also be installed from a tap. Casks can be included in taps with formulae, or in a tap with just casks. Place any cask files you wish to make available in a `Casks` directory at the top level of your tap.

See [homebrew/cask](https://github.com/Homebrew/homebrew-cask) for an example of a tap with a `Casks` subdirectory.

### Naming

Unlike formulae, casks must have globally unique names to avoid clashes. This can be achieved by e.g. prepending the cask name with your github username: `username-formula-name`.

## External commands

You can provide your tap users with custom `brew` commands by adding them in a `cmd` subdirectory. [Read more on external commands](External-Commands.md).

See [homebrew/aliases](https://github.com/Homebrew/homebrew-aliases) for an example of a tap with external commands.

## Upstream taps

Some upstream software providers like to package their software in their own Homebrew tap. When their software is [eligible for Homebrew/homebrew-core](Acceptable-Formulae.md) we prefer to maintain software there for ease of updates, improved discoverability and use of tools such as [formulae.brew.sh](https://formulae.brew.sh).

We are not willing to remove software packaged in Homebrew/homebrew-core in favour of an upstream tap. We are not willing to instruct users of our formulae to use an upstream tap instead. If upstream projects have issues with how Homebrew packages your software: please file issues (or, ideally, pull requests) to address these problems.

There’s an increasing desire in commercial open source about “maintaining control” e.g. defining exactly what binaries are shipping to users. Not supporting users (or even software distributions) to build-from-source is antithetical to the values of open source. If you think Homebrew's perspective is annoying on this: try and see how Debian responds to requests to ship your binaries.
