Advent of Code
freeAnnual December puzzle event
Scaled to 12 puzzles + no global leaderboard in 2025 due to AI solvers and DDoS. Private leaderboards still work. Free.
| URL | https://adventofcode.com |
| Tier | free |
| Relevance | medium |
| Last active signal | AoC 2025 Dec 1-12 (reduced format) |
| Verified alive | yes |
| Category | Competitive |