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Ranked 1v1 duels, free to playStart playing
Grudge
Enter the arena
Competitive coding, head to head

Practice is solitary.
Duels aren’t.

Stop solving problems in a vacuum. Face a real opponent, sharpen your instincts, and find out what you can do when the clock is running.

Start playing See how it works
Free to play No card, no trial Ranked from your first duel
-Problems in the catalog
-Topic chapters
7Languages judged
1200Starting rating
The Grudge difference

Not just another
practice platform.

Great developers are not built by collecting green checkmarks. They are built by making decisions with limited time, incomplete information and a little pressure.

See how a duel works
01

Live duels

Go head to head with a real developer on the same problem, picked near your rating.

Ranked 1v1
02

Instant feedback

Every submission runs against hidden tests the moment you send it. Know where you stand before the clock runs out.

03

Earn your rating

Build a public track record that reflects how you actually perform under pressure.

Starts at 1200
Simple by design

One problem.
One clear winner.

No setup. No endless scrolling. Just a focused challenge and the satisfaction of knowing you got better.

Start a duel
  1. 01 / Get matched

    Meet your opponent

    Queue up and you are paired with someone near your rating, so every duel is a fair fight.

  2. 02 / Solve

    Think under pressure

    Same problem, same countdown. Pick your language, write your solution, watch the clock.

  3. 03 / Improve

    Move your rating

    Elo, not a solve count. Everyone starts at 1200 and wins have to come off someone else.

Built for your workflow

Your language.
The judge’s version.

Use the language you already know. Exact runtimes are published rather than implied, and the catalog is verified against these versions.

PythonPython 3.8.1
C++GCC 9.2.0 (C++17, -O2)
JavaOpenJDK 11.0.23
JavaScriptNode.js 12.16.1
GoGo 1.13.5
RustRust 1.40.0 (-O)
VerilogIcarus Verilog 10.2 (-g2012)
Live rankings

The current
top contenders.

View full podium
RankPlayerTierRating
The difference is clear

Duels vs.
practising alone.

Feature DuelAlone
A real opponent on the same problem
A clock you can actually lose to
A rating that moves with every result
Hidden tests, judged the moment you submit
Untimed practice when you want it
Your next opponent is waiting

Ready when
you are.

Free to play, and ranked from your very first duel.

Enter the arena Free to start · No card required
Questions, answered

Good to know.

Yes. Every mode, every problem and ranked play are free. There is no paid tier and no card to enter.

Ranked duels pair you with someone near your rating, so the fight stays fair. Practice lets you pick any problem from the catalog, untimed and unrated.

No. The editor, the test runner and your results all live in the browser.

Yes. Create an invite link and send it to anyone; they join the same match directly.

An Elo-style system. Everyone starts at 1200, and each result moves both players by an amount that depends on the rating gap between them.