BrokenRepo

It’s broken.
Find out why.

Code debugging practice on real projects — the part tutorials skip. Open an unfamiliar repo, follow the clues, and fix the bug hiding in the code.

Pick your first bugHow practice works

For students and junior engineers. JavaScript, React, and Express.

One bug. Two sides of the request.Example

client / apiClient.js

fetch("/api/dashboard", {
  headers: {
    "x-auth-token": token
  }
});

server / middleware / auth.js

const token = req.headers
  .authorization?.split(" ")[1];

if (!token) {
  return res.status(401);
}
Valid token. Wrong header. Request rejected.

Illustrated example. In the lab, tests execute your code in a real sandbox.

Less blank canvas.
More detective work.

  1. Read the bug report

    A real symptom, a working project, and a file tree to explore. Start by figuring out what should happen.

  2. Trace it through the code

    Follow a request from the client to the server. Edit in the browser. Reveal a hint if you get stuck.

  3. Prove your fix

    Run the hidden tests against your changes. See the actual failures, then try again until the behavior is right.

The bugs you’ll meet
outside a tutorial.

Fifteen focused MERN stack debugging challenges. Each starts with a different real-world failure, so you build a debugging habit beyond a single fix.

Explore the challenges
  • API contractsA name that never appears
  • Async behaviorOld results replacing new ones
  • AuthenticationA valid token getting rejected
  • React stateClicks that don’t add up
  • And eleven moreImports, caching, dates, retries, and more

The same bugs.
Real consequences.

Every category you practice here has shut down a trading firm, a cloud, or a hospital machine. Read the case studies — dissected like our challenges.

Browse famous bugs

Before you
dive in.

Five honest answers about how practice works here.

What is BrokenRepo?
BrokenRepo is a code debugging practice platform. You get a real full-stack MERN repo with a planted bug, a symptom report, and hidden tests — and you fix it in the browser editor.
Do I need to install anything on my machine?
No. The project opens in your browser editor and the tests run in an isolated cloud sandbox, so there is nothing to set up locally.
Who is this for?
Beginners who want debugging practice, freshers preparing for campus placement coding rounds, and SDE-1 candidates working on interview practice.
What kind of bugs will I meet?
Real-world ones: API contract mismatches, race conditions, React state bugs, caching mistakes, timezone and rounding errors — the repo-based question style of online assessments.
Is BrokenRepo free?
Yes. Create an account to save your code and track progress across all fifteen challenges.

Keep the lesson.
Come back for the next bug.

Create an account to save your code, track attempted and solved challenges, and see your progress by category.

Start your debugging practice