Hello Codeforces!

I’d like to share a project I’ve been working on: Clashforces, a free website for competing with friends on Codeforces problems in real time.

https://clashforces.duckdns.org/

Modes Friend duels (1v1 or group rooms). Choose the number of problems, the rating range and the duration. Scoring is either ICPC (solved count, then penalty) or Lockout (the first person to solve a problem takes its points). Ranked queue. Matchmaking by duel rating.

Team matches. 2–6 teams with 2–6 players each, team names, a separate invite link for each team, rating-based auto-balance, or a captains’ draft.

Hosted contests. A host (who doesn’t compete) adds Codeforces problems by ID or link. Problems stay hidden until the start.

After the match: an upsolve list of problems you didn’t solve, plus results history on your profile. How it works

Verdicts: you submit on Codeforces normally. The site reads verdicts through the public Codeforces API, staying within the API’s rate limit of one request every two seconds. Pressing “I submitted” moves you to the front of the check queue, so your verdict shows up within seconds. Login: no password and no Codeforces API key. To prove you own a handle, you submit code that fails to compile to a randomly chosen problem within a short time window.

Problem selection: problems are chosen to avoid ones any participant has already solved.

Why My friends and I enjoyed Lockout-style duels but wanted proper team battles and an easy way to host our own contests on existing problems, with a real ICPC-style reveal at the end. We’re using it for an offline event soon, and I thought others might find it useful too, for example clubs, college groups, or practice with friends.

It’s free with no ads. Please do try this out and would really appreciate your feedback and suggestions.

Happy coding, and good luck in your next round!