CodeCrafters
Challenges
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Build your own Shell
Learn about parsing shell commands, executing programs and more
43 stages
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Build your own grep
Learn about regex syntax: character classes, quantifiers and more
FREE THIS MONTH
This challenge is free until 1 October 2025!
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Build your own Interpreter
Learn about tokenization, ASTs, tree-walk interpreters and more.
84 stages
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Build your own Redis
Learn about TCP servers, the Redis protocol and more
89 stages
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Build your own BitTorrent
Learn about .torrent files, the BitTorrent Peer Protocol and more
19 stages
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Build your own Kafka
Learn about TCP servers, the Kafka wire protocol and more.
FREE DURING BETA
This challenge is free to try when it's in beta. We keep challenges in beta for a few weeks to gather feedback.
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Build your own Git
Learn about git objects, plumbing commands and more
7 stages
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Build your own SQLite
Learn about SQL syntax, SQLite's file format, B-trees and more
9 stages
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Build your own DNS server
Learn about the DNS protocol, DNS record types and more.
8 stages
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Build your own HTTP server
Learn about TCP servers, the HTTP protocol and more
14 stages
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Language Tracks
Rust
Popular
This track is a favourite among our learners.
310 stages
Start
Go
Popular
This track is a favourite among our learners.
310 stages
Start
Python
Popular
This track is a favourite among our learners.
310 stages
Start
C
273 stages
Start
C#
310 stages
Start
C++
310 stages
Start
Clojure
196 stages
Start
Crystal
89 stages
Start
Dart
14 stages
Start
Elixir
258 stages
Start
Gleam
286 stages
Start
Haskell
148 stages
Start
Java
310 stages
Start
JavaScript
310 stages
Start
Kotlin
292 stages
Start
OCaml
173 stages
Start
Odin
192 stages
Start
PHP
235 stages
Start
Ruby
189 stages
Start
Scala
89 stages
Start
TypeScript
310 stages
Start
Zig
310 stages
Start