Is Ruby installed on my Mac? Ruby comes pre-installed on macOS Catalina and Big Sur (see below why you may not want to use the default Ruby). To check if Ruby is installed, enter in your terminal application: $ ruby -v (Don't type the character.) $ If Ruby is not installed, you'll see: zsh: command not found: ruby The command will confirm that Ruby is missing: which $ which ruby ruby not found You can use the command with flag to see if more than one Ruby executable is installed: which -a $ which -a ruby /Users/daniel/.asdf/shims/ruby /usr/bin/ruby If Ruby is installed, the command will show a response like: ruby -v $ ruby -v ruby p62 2.6 .3 MacOS comes with a "system Ruby" pre-installed. Use the `which` command to see if you are using the system Ruby: $ which ruby /usr/bin/ruby If you see , it is the pre-installed macOS system Ruby. It's fine to use the system Ruby for running sysadmin scripts, as long as you don't alter the system Ruby by attempting to update it or add gems. But experienced developers don't use the system Ruby for developing projects in Ruby. /usr/bin/ruby because it is an older version of Ruby. Instead, you can . You could also use a version manager such as asdf, chruby, rbenv, or rvm. A version manager can also help if you're juggling multiple projects that can't be updated all at once. You may not want to use the MacOS system Ruby Install Ruby with Homebrew For a guide that compares version managers and shows the best way to install Ruby, see . If you're going to build web applications with Rails, see . Install Ruby on a Mac Install Ruby on Rails on a Mac Also published on Dev.to .