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CodeCrafters | Advanced programming challenges 
Backed by Y CombinatorTrain your engineering
Projects that go way
Be in the company of
Use your favourite
Backed by Y CombinatorTrain your engineering
skills like a pro athlete
Recreate tools like Git, Redis, and SQLite from scratch.
Practice debugging and refactoring code under constraints.
Become the engineer others trust with their hardest problems.
Practice debugging and refactoring code under constraints.
Become the engineer others trust with their hardest problems.
Enjoyed by developers at the world’s best companies:
Backed by incredible engineers
These fine folks believe in the CodeCrafters approach.
Mike Krieger
Co-founder/CTO, Instagram
Arash Ferdowsi
Co-founder/CTO, Dropbox
JJ Kasper
Maintainer of Next.js
Jitendra Vaidya
Co-founder, PlanetScale
Paul Copplestone
Co-Founder, Supabase
Hear it from our members
Engineers at top teams love The CodeCrafters Way™
These guys ruined my weekend
Djordje Lukic
Docker contributor
There are few sites I like as much that have a step by step guide. The real-time feedback is so good, it's creepy!
Ananthalakshmi
Engineer at Apple
I spent a full day on your course and ended up building the whole thing myself. As a SRE (and mostly a user of SQLite), digging into the internals blew me away.
Raghav Dua
SRE at Coinbase
The Redis challenge was a great way to procrastinate sleeping for a week! A good change of pace from my regular work, and allowed me to explore some cool tech. I'll be back for more.
Rahul Tarak
Pioneer.app & ODX1 Fellow
The Redis challenge was extremely fun. I ended up having to read Redis protocol specification doc pretty carefully in its entirety! The result felt like lightly-guided independent study, if that makes sense. (Which, again, was lots of fun)
Charles Guo
Scala Team at Stripe
I'm learning about how Redis works under the hood, system calls, socket programming in Python; something I've never done before
Akshata Mohan
Senior Data Scientist at Cloudflare
My favorite way to master a language.
Pranjal Paliwal
Winner of HackAtom
I’ve started the SQLite challenge, enjoying it a lot so far. Just the right level of guidance, helpful yet gives you a lot of freedom to explore and learn for yourself.
Cindy Wu
Participant at Recurse Center
In a perfect world, job interviews ask for assignments like CodeCrafters instead of Leetcode.
The best way to refresh your programming language skills and learn something new about Redis, Git, SQLite internals.
Vladislav Ten
SWE at Microsoft
The challenge helped me dive into its internals, through *actual* practice. Super fun.
Kang Ming Tay
SWE at Supabase
I was really impressed that they support Haskell, and will probably usethis to learn Rust! The git-based workflow is :chefkiss:
Jonathan Lorimer
Lead SWE at Mercury Bank
Found out from a colleague. It has you build your own version of things like Git and SQLite from scratch. A cool way to build a stronger mental model of how those tools work.
Beyang Liu
CTO at SourceGraph
Projects that go way
beyond the basics
Build software deeper than simple CRUD apps. Take on projects involving storage engines, protocols, concurrency and performance.
Become the engineer who's comfortable with complexity.
Become the engineer who's comfortable with complexity.
I'm learning about how Redis works under the hood, system calls, socket programming in Python; something I've never done before
Akshata Mohan
Senior Data Scientist at Cloudflare
Be in the company of
prolific engineers
See how contributors to projects like Docker and Rails refactor, how engineers who build large-scale systems debug, and how CTOs of developer platforms make architectural decisions.
Improve your taste by observing other great engineers.
Improve your taste by observing other great engineers.
The Redis challenge was extremely fun. I ended up having to read Redis protocol specification doc pretty carefully in its entirety! The result felt like lightly-guided independent study, if that makes sense. (Which, again, was lots of fun)
Charles Guo
Scala Team at Stripe
Use your favourite
tools to code. No limits.
Don't be limited by web-based editors. Code in your usual IDE, with your preferred customisations. Push code with Git and get instant feedback. Share your work on GitHub.
CodeCrafters is designed for pros.
CodeCrafters is designed for pros.
There are few sites I like as much that have a step by step guide. The real-time feedback is so good, it's creepy!
Ananthalakshmi
Engineer at Apple