Learn CRYSTAL with Real Code Examples

Crystal compiles directly to native code for high performance.

It features static type checking with powerful type inference, reducing boilerplate.

Used for web development, CLI tools, system utilities, and high-performance applications.

Classes, modules, structs, and enums

Generics and type inference

Error handling with exceptions

Compile-time macros

Standard library for networking, HTTP, JSON, and more

Crystal syntax and expressions

Variables, types, and constants

Classes, structs, and modules

Methods, blocks, and lambdas

Error handling with `raise` and `rescue`

src/ (source code)

lib/ (dependencies via Shards)

spec/ (unit tests)

shard.yml (dependency config)

bin/ (compiled binaries)

Write `.cr` source files

Manage dependencies with Shards

Compile using `crystal build file.cr`

Run compiled binary

Debug with compiler warnings and logging

Beginner: CLI utilities and small scripts

Intermediate: web apps with Kemal or Amber

Advanced: concurrent microservices

Expert: system-level high-performance tools

Syntax similar to Ruby, but compiled and statically typed

Faster than interpreted languages like Ruby or Python

Less mature ecosystem than mainstream languages

Macro system allows metaprogramming unlike Go

Concurrency model simpler than full OS threads

2011 – Crystal first introduced

2014 – Shards dependency manager released

2016 – Kemal web framework launched

2018 – Amber web framework stabilization

2020–2025 – Compiler improvements and ecosystem growth

Shards: Crystal’s package manager

Fiber: lightweight concurrency primitive

Macro: compile-time code generator

Spec: built-in testing module

Type inference: compiler deduces variable types