Crystal Programming Language

This is the language reference for the Crystal programming language.

Crystal is a programming language with the following goals:

  • Have a syntax similar to Ruby (but compatibility with it is not a goal).
  • Be statically type-checked, but without having to specify the type of variables or method parameters.
  • Be able to call C code by writing bindings to it in Crystal.
  • Have compile-time evaluation and generation of code, to avoid boilerplate code.
  • Compile to efficient native code.

Crystal's standard library is documented in the API docs.

Contributing to the Language Reference

Do you consider yourself a helpful person? If you find bugs or sections which need more clarification you're welcome to contribute to this language reference. You can submit a pull request to this repository:

Thank you very much!

Building and Serving Locally

$ git clone
$ cd crystal-book

Live preview (at

$ make serve
INFO    -  Building documentation...
INFO    -  Cleaning site directory
INFO    -  Documentation built in 3.02 seconds
INFO    -  Serving on

Build into the site directory (some functionality won't work if opening the files locally):

$ make build

Adding a page

To add a page, create a Markdown file in the desired location. Then, add a link in the file which acts as the navigation for the language reference.

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Mon, 02 Aug 2021 11:34:16 GMT