A tap is homebrew-speak for a Git repository containing extra formulae. Homebrew has the capability to add (and remove) multiple taps to your local installation with the brew tap and brew untap commands. Type man brew in your Terminal. The main repository https://github.com/Homebrew/homebrew-core, often called homebrew/core, is always built-in.
brew search looks in these taps as well as in homebrew/core so don’t worry about missing stuff.
You can be added as a maintainer for one of the Homebrew organization taps and aid the project! If you are interested please feel free to ask in an issue or pull request after submitting multiple high-quality pull requests. We want your help!
denji/nginx: A tap for NGINX modules, intended for its nginx-full formula which includes more module options.
InstantClientTap/instantclient: A tap for Oracle Instant Client. The packages need to be downloaded manually.
osx-cross/avr: GNU AVR toolchain (Libc, compilers and other tools for Atmel MCUs, useful for Arduino hackers and AVR programmers).
petere/postgresql: Allows installing multiple PostgreSQL versions in parallel.
titanous/gnuradio: GNU Radio and friends running on macOS.
dunn/emacs: A tap for Emacs packages.
sidaf/pentest: Tools for penetration testing.
osrf/simulation: Tools for robotics simulation.
mistydemeo/tigerbrew: Experimental Tiger PowerPC version
Linuxbrew/brew: Experimental Linux version
Your taps are Git repositories located at $(brew --repository)/Library/Taps.
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Licensed under the BSD 2-Clause License.
https://docs.brew.sh/Interesting-Taps-and-Forks.html