How to create a new Rails app with a specific version of Rails

Imagine you want to try out a new Ruby on Rails version, or have to use an old version for some strange reason.

Here’s how to install an old version of Rails and create a new project with it:

1. Install your chosen version of version of Rails

Take a look at https://github.com/rails/rails/releases for all versions, copy the tag name exactly, and add it as the --version argument of gem install rails

$ gem install rails --version 7.1.0.beta1

2. Create a new app with the newly installed rails version:

You do to this by providing the Rails version after rails and before new, with an underscore in front and after the version. This will look for a railties gem with a matching version and executable rails binary, e.g:

$ rails _7.1.0.beta1_ new my_app

And that’s it, your new app awaits.