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Using the Ruby Runtime with Vercel Functions

Last updated October 27, 2025

The Ruby runtime is available in Beta on all plans

The Ruby runtime is used by Vercel to compile Ruby Vercel functions that define a singular HTTP handler from files within an directory at your project's root.

Ruby files must have one of the following variables defined:

  • proc that matches the signature.
  • class that inherits from the class.

For example, define a file inside a directory as follows:

An example index.rb file inside an /api directory.

Inside a define:

An example Gemfile file that defines cowsay as a dependency.

New deployments use Ruby 3.3.x as the default version.

You can specify the version of Ruby by defining in a , like so:

If the patch part of the version is defined, like 3.3.1 it will be ignored and assume the latest 3.3.x.

This runtime supports installing dependencies defined in the . Alternatively, dependencies can be vendored with the command (useful for gems that require native extensions). In this case, dependencies are not built on deployment.


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