brew/docs/Acceptable-Formulae.md

# Acceptable Formulae

Some formulae should not go in
[homebrew/core](https://github.com/Homebrew/homebrew-core). But there are
additional [Interesting Taps & Forks](Interesting-Taps-&-Forks.md) and anyone can start their
own!

### We try hard to avoid dupes in `homebrew/core`
Stuff that comes with macOS or libraries that are provided by
[RubyGems, CPAN or PyPi](Gems,-Eggs-and-Perl-Modules.md)
should not be duplicated. There are good reasons for this:

* Duplicate libraries regularly break builds
* Subtle bugs emerge with duplicate libraries, and to a lesser extent,
  duplicate tools
* We want our formulae to work with what comes with macOS

There are exceptions:

* OpenSSL - Apple has formally deprecated OpenSSL on macOS in favour of their own Security Framework
  & consequently the macOS OpenSSL is rarely updated and frequently falls behind important security updates.
  Homebrew endeavours to use our shipped OpenSSL as much as possible.
* Programs that a user will regularly interact with directly, like editors and
  language runtimes
* Libraries that provide functionality or contain security updates not found in
  the system version
* Things that are **designed to be installed in parallel to earlier versions of
  themselves**

#### Examples

| Formula            | Reason                                                                                                |
|--------------------|-------------------------------------------------------------------------------------------------------|
| ruby, python, perl | People want newer versions                                                                            |
| bash               | macOS's bash is stuck at 3.2 because newer versions are licensed under GPLv3                          |
| zsh                | This was a mistake, but it’s too late to remove it                                                    |
| emacs, vim         | [Too popular to move to dupes](https://github.com/Homebrew/homebrew/pull/21594#issuecomment-21968819) |
| subversion         | Originally added for 10.5, but people want the latest version                                         |
| libcurl            | Some formulae require a newer version than macOS provides                                             |
| openssl            | macOS's openssl is deprecated & outdated                                                              |
| libxml2            | Historically, macOS's libxml2 has been buggy                                                          |

### We don’t like tools that upgrade themselves
Software that can upgrade itself does not integrate well with Homebrew's own
upgrade functionality.

### We don’t like install-scripts that download things
Because that circumvents our hash-checks, makes finding/fixing bugs
harder, often breaks patches and disables the caching. Almost always you
can add a resource to the formula file to handle the
separate download and then the installer script will not attempt to load
that stuff on demand. Or there is a command-line switch where you can
point it to the downloaded archive in order to avoid loading.

### We don’t like binary formulae
Our policy is that formulae in the core tap
([homebrew/core](https://github.com/Homebrew/homebrew-core)) must be open-source
and either built from source or produce cross-platform binaries (e.g. Java).
Binary-only formulae should go to
[Homebrew Cask](https://github.com/caskroom/homebrew-cask).

### Stable versions
Formulae in the core repository must have a stable version tagged by
the upstream project. Tarballs are preferred to Git checkouts, and
tarballs should include the version in the filename whenever possible.

We don’t accept software without a tagged version because they regularly break
due to upstream changes and we can’t provide [bottles](Bottles.md) for them.

### Bindings
First check that there is not already a binding available via
[`gem`](https://rubygems.org/) or [`pip`](http://www.pip-installer.org/)
etc.

If not, then put bindings in the formula they bind to. This is more
useful to people. Just install the stuff! Having to faff around with
foo-ruby, foo-perl etc. sucks.

### Niche (or self-submitted) stuff
The software in question must:

* be maintained (e.g. upstream is still making new releases)
* be known
* be stable (e.g. not declared "unstable" or "beta" by upstream)
* be used
* have a homepage

We will reject formulae that seem too obscure, partly because they won’t
get maintained and partly because we have to draw the line somewhere.

We frown on authors submitting their own work unless it is very popular.

Don’t forget Homebrew is all Git underneath!
[Maintain your own tap](How-to-Create-and-Maintain-a-Tap.md) if you have to!

There may be exceptions to these rules in the main repository; we may
include things that don't meet these criteria or reject things that do.
Please trust that we need to use our discretion based on our experience
running a package manager.

### Stuff that builds an `.app`
Don’t make your formula build an `.app` (native macOS Application); we
don’t want those things in Homebrew (but
[Homebrew Cask](https://github.com/caskroom/homebrew-cask) does).
Make it build a command-line tool or a library.

### Sometimes there are exceptions
Even if all criteria are met we may not accept the formula.
Documentation tends to lag behind current decision-making. Although some
rejections may seem arbitrary or strange they are based on years of
experience making Homebrew work acceptably for our users.