Skip to content


Switch branches/tags

Name already in use

A tag already exists with the provided branch name. Many Git commands accept both tag and branch names, so creating this branch may cause unexpected behavior. Are you sure you want to create this branch?


Failed to load latest commit information.
Latest commit message
Commit time


github build status MIT License badge

Natalie is a very early-stage work-in-progress Ruby implementation.

It provides an ahead-of-time compiler using C++ and gcc/clang as the backend. Also, the language has a REPL that performs incremental compilation.

demo screencast

There is much work left to do before this is useful. Please let me know if you want to help!

Helping Out

Contributions are welcome! You can learn more about how I work on Natalie via the hacking session videos on YouTube.

The easiest way to get started right now would be to find a method on an object that is not yet implemented and make it yourself! Also take a look at good first issues. (See the 'Building' and 'Running Tests' sections below for some helpful steps.)

We have a very quiet Discord server -- come and hang out!


Natalie is tested on macOS, OpenBSD, and Ubuntu Linux. Windows is not yet supported.

Natalie requires a system Ruby (MRI) to host the compiler, for now.


  • git
  • autoconf
  • automake
  • libtool
  • GNU make
  • gcc or clang
  • Ruby 2.7 or higher with dev headers
    • Using rbenv to install Ruby is preferred.
    • Otherwise, you'll need the ruby and ruby-dev package from your system.
  • ccache (optional, but recommended)
  • compiledb (optional, but recommended)

Install the above prerequisites on your platform, then run:

git clone
cd natalie

Troubleshooting Build Errors

  • Don't use sudo! If you already made that mistake, then you should sudo rm -rf build and try again.
  • If you get an error about file permissions, e.g. unable to write a file to somewhere like /usr/lib/ruby, or another path that would require root, then you have a couple options:
    • Use a tool like rbenv to install a Ruby verison in your home directory. Gems will also be installed there. Run rbenv version to see which version is currently selected. Run rbenv shell followed by a version to select that version.
    • Specify where to install gems with something like:
      mkdir -p ~/gems
      export GEM_HOME=~/gems
      You'll just have to remember to do that every time you open a new terminal tab.
  • If you get an error about missing bundler, then your operating system probably didn't install it alongside Ruby. You can run gem install bundler to get it.

NOTE: Currently, the default build is the "debug" build, since Nataile is in active development. But you can build in release mode with rake build_release.




Run a Ruby script:

bin/natalie examples/hello.rb

Compile a file to an executable:

bin/natalie -c hello examples/hello.rb

Using With Docker

docker build -t natalie .                                            # build image
docker run -it --rm natalie                                          # repl
docker run -it --rm natalie -e "p 2 * 3"                             # immediate
docker run -it --rm -v$(pwd)/myfile.rb:/myfile.rb natalie /myfile.rb # execute a local rb file
docker run -it --rm --entrypoint bash natalie                        # bash prompt

Running Tests

To run a test (or spec), you can run it like a normal Ruby script:

bin/natalie spec/core/string/strip_spec.rb

This will run the tests and tell you if there are any failures.

If you want to run all the tests that we expect to pass, you can run:

rake test

Lastly, if you need to run a handful of tests locally, you can use the test/runner.rb helper script:

bin/natalie test/runner.rb test/natalie/if_test.rb test/natalie/loop_test.rb

What's the difference between the 'spec/' and 'test/' directories?

The files in spec/ come from the excellent ruby/spec project, which is a community-curated repo of test files that any Ruby implementation can use to compare its conformance to what MRI (Matz's Ruby Interpreter) does. We copy specs over as we implement the part of the language that they cover.

Everything in test/ is stuff we wrote while working on Natalie. These are tests that helped us bootstrap certain parts of the language and/or weren't covered as much as we would like by the official Ruby specs. We use this to supplement the specs in spec/.

Copyright & License

Natalie is copyright 2021, Tim Morgan and contributors. Natalie is licensed under the MIT License; see the LICENSE file in this directory for the full text.

Some parts of this program are copied from other sources, and the copyright belongs to the respective owner. Such copyright notices are either at the top of the respective file, in the same directory with a name like LICENSE, or both.

file(s) copyright license
big_int.* Syed Faheel Ahmad MIT
dtoa.c David M. Gay, Lucent Technologies custom permissive
fiber_object.* Evan Jones MIT
spec/* Engine Yard, Inc. MIT
version.rb Engine Yard, Inc. MIT
zlib Jean-loup Gailly and Mark Adler zlib license

See each file above for full copyright and license text.