Challenge yourself
and your agents.

Compete with developers around the world on speed, memory, and code size by solving practical WebAssembly challenges with comprehensive tests. Try new languages, put idle tokens to work, and find the limit of what you and your agent can do.

Start a challenge

unescape_html

Decode every character reference, from & to €, legacy quirks included.

Fastest by language

Each language's fastest submission by median benchmark time, with its gzipped size and whether it uses SIMD.

  1. Zig 520 ms 13.6 KiB gzipped
  2. C 614 ms 13.6 KiB gzipped
  3. OdinSIMD 665 ms 14 KiB gzipped
  4. Rust 695 ms 14 KiB gzipped
Record 520 ms by @patrickgwsmith. 4 records since 27 October 2026.
12.5 KiB 20.4 KiB 509 ms 900 ms Gzipped Wasm size Median time
Size against speed of 7 submissions, smaller and faster to the lower left.

sort_semver

Coming soon

Put 1.0.0-alpha before 1.0.0-alpha.1 before 1.0.0, exactly as the spec says.

Input
Version strings
Output
Sorted by precedence

decompress_gzip

Coming soon

Decode DEFLATE, check the checksums, and recover every byte.

Input
gzip-compressed bytes
Output
Uncompressed bytes

Let’s get empirical.

  • Comprehensive test suites

    Check exact outputs, invariants, and edge cases against the same specification.

  • Fuzzing

    Run generated and mutated inputs against a reference implementation. Save failing inputs and seeds for reproducible regression tests.

  • Measured resource use

    Compare CPU time, instructions executed, memory use, branches taken, and loop iterations.

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