UrsaCode

Case study · Our own product

Regex Hunter

A daily regex game: one puzzle a day, the same for everyone, won by the shortest pattern.

  • Live sinceJune 2026
  • What we didProduct, game design, web app, backend
  • Live atregexhunter.com
Play today's hunt
Regex Hunter's daily hunt: 5 words to catch, 5 to spare, and a box to type the shortest regular expression that tells them apart.
69daily puzzles in the public archive
25 mstime limit on every match, so no pattern can stall the server
1,000+automated tests across the app and API
4languages: English, French, Spanish and Chinese

As of 12 October 2026.

01The idea

Regex golf, writing the shortest pattern that matches one list of words and not another, has been a favourite programmer puzzle since xkcd made it famous in 2014. It never had a daily, shared, scored format.

Regex Hunter gives it one: the same board for everyone each day, a leaderboard that rewards the shortest answer, streaks and share cards, plus practice and lessons for people still learning.

02What we built

  • The daily hunt. Catch every "monster" word, spare every "innocent" one, in as few characters as you can.
  • Hunting Spree. Real-time races against other players, with a shared countdown.
  • The Academy. 9 tracks of lessons, with certificates anyone can check.
  • Community. Player-made hunts, discussions, teams and concept leaderboards.
  • Reach without manual work. Short explainer videos rendered from the puzzles and queued for Instagram, YouTube Shorts and TikTok automatically.

03The hard parts

Scores the browser can't fake

Every answer is re-checked on the server. Patterns are capped at 64 characters and each match has 25 ms, so a pathological regex can't stall the server. A translator keeps JavaScript's regex rules on the Python side, so the board and the server always agree.

Fair play

Answers stay hidden on leaderboards, regex flags cost a character each, and puzzle authors can't score on their own hunts.

Live races at scale

Race events fan out to every server worker through Redis, fall back to a single worker if Redis is down, and reconnect on their own after a restart.

04Where it stands

Live since June 2026, launched on Product Hunt in July, with daily puzzles scheduled through the end of the year. Work continues: a redesigned site, notifications and pinned discussions all landed in October.

Regex Hunter on a phone.
The same hunt on a phone

05Built with

  • Next.js
  • React
  • FastAPI
  • PostgreSQL
  • Redis
  • WebSockets
  • Cloudflare

Related service: Web apps and MVPs.

Building something people come back to daily?

Games, real-time features and the backend that keeps them fair.

Start a project