You can tell it for a given project by looking in Gemfile.lock. It shows all the gems you explicitly requested in your Gemfile, and what dependencies each one

You can tell it for a given project by looking in Gemfile.lock. It shows all the gems you explicitly requested in your Gemfile, and what dependencies each one pulled in. edit: assuming you're using Bundler, that is. If you're not, fix that first ;)