Code Battle

About

Code Battle turns Codeforces into a head-to-head arena.

⚔ Two players, real Codeforces problems
Race a friend in a private room, or queue for a ranked match against
a Codeforces user within ±500 of your rating. First Accepted submission
takes the round. Best of 3 wins the match.

Everything happens on one page
The problem and the official Codeforces editor are embedded side by
side inside Codeforces' own /battle page. No tab switching, no copy-
pasting, no leaving the site you already know.

Ranked leaderboard with Elo
Verify your handle once with your Codeforces API key and your ranked
matches will count toward a global Elo leaderboard. Friend-room games
are casual and do not affect rating.

Privacy-first opponent view
You can see that your opponent is coding — typing pulses, line count,
caret position — but you never see what they are typing. The "ghost
code" preview is generated locally from a hash of their handle; their
real source code never leaves their browser.

What it does NOT do
- Does not read or upload your source code
- Does not share data with third parties
- Does not require your Codeforces password (API key signing only)
- Does not track your browsing history

Open https://codeforces.com/battle after installing.

Made by Reza Shiri. Not affiliated with or endorsed by Codeforces.