29th IOCCC 2025 winners announced: masters of obfuscated C code

The International Obfuscated C Code Contest (IOCCC) has published the winners of its 29th edition, IOCCC 2025. According to the organisers, the volume and quality of submissions were at near-historic heights this year, and it was only the second contest held since the four-year hiatus of 2020–2024.

The contest and its scale

After IOCCC28 closed, the judges documented in detail the procedures used to close the contest, judge entries, select winners and prepare the website update. That documentation took extra time and effort, but the organisers say it improved how the contest is run overall. The final rules and guidelines in effect for this contest — rules version 29.15 and guidelines version 29.08, both dated 2 December 2025 — represent a substantial rewrite of earlier versions, helped by volunteers who contributed edits, text rewrites and consolidation.

Winning entries

Among the IOCCC29 winners are a Subleq computer (2025/cable), a “black hole punchcard Fortran” entry (2025/cesmoak), a patch/diff quine (2025/endoh3), a quasi-rogue-like game (2025/jhshrvdp), a Dr. WHO sequence (2025/jingp49), a GameBoy emulator (2025/ncw1), an ocean sound generator (2025/tompng), a quine pong (2025/uellenberg) and a Zoltraak encoding (2025/yang2). Awards range from “Best one liner” and “Best real emulator” to “Most soothing”, “Most likely to teleport” and “Most obfuscated options”.

Three authors scored a hat trick of hat tricks: Yusuke Endoh (2025/endoh1–3), Nick Craig-Wood (2025/ncw1–3) and Don Yang (2025/yang1–3) each landed three winning entries. The contest also gained an author from a new location — jingp49, from Taiwan — the first time that country has appeared among winning authors.

What comes next

The winners were presented on the “Our Favorite Universe” YouTube channel a few days after the entries were posted. The recording of the main show will be divided into individual segments, and each winning entry’s page will gain a link to its segment under a new “Award presentation” heading. All of the 2025 winning source code is also available as a single downloadable tarball.

The judges plan to open IOCCC30 towards the end of 2026, run it for a similar amount of time, and close it sometime towards the end of the first quarter of 2027.