The Crystal Programming Language

Crystal is a general-purpose, object-oriented programming language. With syntax inspired by Ruby, it’s a compiled language with static type-checking. Types are resolved by an advanced type inference algorithm.
Crystal’s standard library comes with a whole range of libraries that let you start working on your project right away.
The compiler catches type errors early. Avoids null pointer exceptions at runtime.
The code is still clean and feels like a dynamic language.
The compiler tracks the type of variables at each point, and restricts types according to conditions.
Crystal uses green threads, called fibers, to achieve concurrency. Fibers communicate with each other via channels without having to turn to shared memory or locks (CSP).
Bindings for C libraries makes it easy to use existing tools. Crystal calls lib functions natively without any runtime overhead.
No need to implement the entire program in Crystal when there are already good libraries for some jobs.
Crystal’s answer to metaprogramming is a powerful macro system, which ranges from basic templating and AST inspection, to types inspection and running arbitrary external programs.
Crystal libraries are packed with Shards, a distributed dependency manager without a centralised repository.
It reads dependencies defined in shard.yml and fetches the source code from their repositories.
Two and a half years ago, with the invaluable support from 84codes, we re-examined the multithreading model inherited from Crystal 0.28 (preview MT).
On 12 April 2026, we received a vulnerability report regarding an HTTP request smuggling vulnerability in HTTP::Server.
Finally, starting with Crystal 1.19 we provide official ARM64 builds
Johannes is speaking about Crystal at FOSDEM 2026 in Brussels.
Become a Crystal sponsor in only 3 simple steps via OpenCollective
Sponsoring Crystal creates a great springboard for your brand
You can tap into the expertise of the very creators of the language to guide you in your implementation.
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Licensed under the Apache License, Version 2.0
Crystal language, born & raised at Manas