CodeCrafters
Challenges
New here?
Start here
to learn how challenges work.
Build your own Shell
Learn about parsing shell commands, executing programs and more
FREE THIS MONTH
This challenge is free until 1 January 2026!
Start
Build your own Redis
Learn about TCP servers, the Redis protocol and more
97 stages
Build your own grep
Learn about regex syntax: character classes, quantifiers and more
33 stages
Build your own Interpreter
Learn about tokenization, ASTs, tree-walk interpreters and more.
84 stages
Build your own BitTorrent
Learn about .torrent files, the BitTorrent Peer Protocol and more
19 stages
Build your own Kafka
Learn about TCP servers, the Kafka wire protocol and more.
25 stages
Build your own Git
Learn about git objects, plumbing commands and more
7 stages
Build your own SQLite
Learn about SQL syntax, SQLite's file format, B-trees and more
9 stages
Build your own DNS server
Learn about the DNS protocol, DNS record types and more.
8 stages
Build your own HTTP server
Learn about TCP servers, the HTTP protocol and more
14 stages
Language Tracks
Rust
Popular
This track is a favourite among our learners.
339 stages
Start
Go
Popular
This track is a favourite among our learners.
339 stages
Start
Python
Popular
This track is a favourite among our learners.
339 stages
Start
C
339 stages
Start
C#
339 stages
Start
C++
339 stages
Start
Clojure
204 stages
Start
Crystal
97 stages
Start
Dart
14 stages
Start
Elixir
291 stages
Start
Gleam
315 stages
Start
Haskell
170 stages
Start
Java
339 stages
Start
JavaScript
339 stages
Start
Kotlin
339 stages
Start
OCaml
181 stages
Start
Odin
214 stages
Start
PHP
271 stages
Start
Ruby
197 stages
Start
Scala
195 stages
Start
TypeScript
339 stages
Start
Zig
339 stages
Start