Advent of Code is a free annual programming puzzle event created by Eric Wastl. A new puzzle unlocks each day starting December 1, in any language you like. Puzzles get harder as the days go on, and you can solve them at any skill level. It trains problem solving more than any one language.
What is Advent of Code?
Advent of Code is a set of small programming puzzles released daily in December, in the style of an advent calendar. Eric Wastl builds all of it himself at adventofcode.com. It has run every year since 2015.
You get a puzzle and a personal input file. You write a program in whatever language you want and submit the answer. Solving part one unlocks part two. There is no sign-up fee, and you can log in with GitHub, Google, Reddit or X.
The length and some rules have changed over the years, so check the about page for the current schedule and leaderboard rules before you plan your December.
Why developers treat it as a tradition
A lot of streamers and developers do it every year, ThePrimeagen among them. That is where the "Primeagen tradition" in the old title of this post came from. It is a shared yearly event: you can compare notes with other people on the same puzzle on the same day.
The puzzles are small enough to finish in an evening and varied enough to teach something. Early days are approachable for newcomers. Later days push you into the kind of algorithms and data structures thinking that interviews and real performance problems reward.
My take
I keep coming back to Advent of Code because it is about continuous learning, not just puzzles. It builds resilience and perseverance, and it connects you with a global community of developers. The habits carry over into everyday professional coding, and it is a good way to practice a new language, which fits with learning to code in 2026.
I eagerly await each new edition. Join me next December and treat every puzzle as a step toward better problem solving.
Frequently Asked
Is Advent of Code free? Yes. The puzzles are free. Eric Wastl funds it through optional support from participants and sponsors.
When does Advent of Code start? Puzzles unlock at midnight US Eastern time, beginning December 1. Check the site for the current year's number of days.
Which language should I use for Advent of Code? Any. Pick the one you want to practice. The answer is a number or string you submit, so the language doesn't matter.
Do I need to know algorithms to take part? No. The first days need basic loops and parsing. Later days reward knowing graphs, dynamic programming and similar techniques, which you can learn as you go.