Puzzles without an account: 9 to try
Try 9 puzzles. Start with a warm-up or choose a topic that interests you. Nothing to install.
Solve without logging in. A free account unlocks the remaining puzzles, saved progress and points.
- Start here Warm-up Coding Modify the code Unlock access 10 pts
- Warm-up Coding Write a function Is it even? 10 pts
- Warm-up DevTools Find the flag Flag in a comment 10 pts
- Easy DevTools Tamper the request The role cookie 20 pts
- Easy Coding Real-life challenges Write a function Product limit: zero is a setting 20 pts
- Medium Analysis Predict the output Truthy and default values 30 pts
- Medium DevTools Tamper the request Forged role token (Base64) 30 pts
- Medium Analysis Predict the output Async Order 30 pts
- Medium Coding Real-life challenges Write a function The webhook arrived twice 30 pts
Challenge types - several ways to play
Coding, analysis and DevTools cover twelve challenge types. The Real-life category brings together practical application problems. Explore every type below.
Write and improve code
Write functions, fix bugs and test your solutions. Practice reading code and solving problems.
- Write a function → Write a function - build a solution from scratch. Trains clean coding and algorithms.
- Find and fix the bug → Find and fix the bug - the starter contains a defect. Trains reading other people's code and debugging.
- Modify the code → Unlock the goal - change locked code so it returns the expected value. Trains reasoning about conditions.
- Shortest code (golf) → Shortest code (golf) - solve it, but length counts. Fit within the character limit and beat the shortest-solution record. Trains conciseness and language tricks.
- Program the output → Program the output - the reverse of "Predict the result": write code that prints exactly the given string to the console. Trains control over what reaches the output.
Understand JavaScript
Predict output, understand type conversions and work out the order of asynchronous operations.
- Predict the output → Predict console output. Test your understanding of type conversions, variable scope and execution order.
- Decode → Decode the string - decipher data (Base64, ROT13, Caesar cipher). Trains recognising encodings.
- Write a regular expression → Match the required strings and reject the others. Practice regular expressions with concrete examples.
- Shortest regex (golf) → Shortest regex (golf) - hit every "match" and no "skip" using as few characters as possible. Trains regex and minimalism.
- Spot the vulnerability → Read a code snippet and identify a vulnerability, such as XSS or a data leak. Practice spotting security issues.
Practice with DevTools
Find hidden values, inspect headers and modify HTTP requests in purpose-built puzzles.
- Find the flag → Find the flag - locate a hidden value in DevTools (HTML comment, header, localStorage, XHR). Trains recon.
- Tamper the request → Change a request parameter, cookie or header to obtain a hidden value. Practice working with HTTP.
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