What does brew tap mean?

Sometimes I see articles saying command of brew tap before brew install something. I am wondering what does tap mean? And why must I run tap before install?


  • The tap command allows Homebrew to tap into another repository of formulae. Once you've done this you've expanded your options of installable software.

    These additional Git repos (inside /usr/local/Homebrew/Library/Taps) describe sets of package formulae that are available for installation.


    brew tap                     # list tapped repositories
    brew tap <tapname>           # add tap
    brew untap <tapname>         # remove a tap