IOCCC 2025: 29th Obfuscated C Contest Crowns Winners, Triple Hat-Tricks

The 29th International Obfuscated C Code Contest has announced its 2025 winners, marking the second consecutive year the competition has run after a four-year hiatus from 2020 to 2024. Submission volume and quality held at near-historic highs, which the judges attribute to refined website design, social media presence, and authors iterating on past winning techniques. Three authors pulled off hat-tricks with three winning entries each: Yusuke Endoh, Nick Craig-Wood, and Don Yang. The contest also welcomed its first winner from Taiwan, jingp49.

Standout entries include a Subleq one-instruction computer, a black-hole-themed punchcard Fortran program, a patch/diff quine, a GameBoy emulator, an ocean sound generator, and a playable Pong implemented as a quine. New this year, each winning entry includes a ‘fun challenge’ inviting readers to extend or explain the code via GitHub pull requests. Presentations of the winners will be released as segments on the Our Favorite Universe YouTube channel and linked back from each entry’s page.

The judges plan to take an extended break after handling early pull requests, deferring work on the mkiocccentry submission tooling until after that vacation. IOCCC30 is targeted to open in late 2026 and close around the end of Q1 2027. Authors whose submissions did not win this round are encouraged to resubmit — multiple 2025 winners were polished versions of entries that previously fell short.