Slap Derby is a free, motion-controlled power-slap game you play with nothing but a webcam. Five opponents walk onto the mark under the arena lights, plant their feet, clasp their hands behind their backs and brace. You get one strike each: swing your real arm across their face and the camera reads how fast your hand was moving and how much body you put behind it.
The body answers live — a flinch, a stagger across the stage, a drop to the knees, or a stiff, out-cold knockout on the mat — then a slow-motion replay shows the hit from ringside before the damage card tells you what broke. Damage plus knockdown bonuses add up to your score.
How Slap Derby works
Your webcam reads your upper body in real time using on-device pose tracking — nothing is uploaded, and the camera feed never leaves your browser. You only need your shoulders and hands in view, so you can stand close. A dedicated hand tracker follows your striking hand at the camera’s full frame rate and shows it as a glowing palm in front of your opponent’s face. Line it up and swing through, fast and level.
A slap is momentum, not just speed: your body weight, a straight arm and turning your torso into it all add mass behind the hand. Where you connect matters too — the cheek is the clean shot, the jaw is the knockout button, the temple rattles the skull. Too gentle is a pat, and a swing over their head or under the chin is a whiff.
Upper-body power, disguised as a prize fight
Every strike is a short, explosive full-arm swing driven from the hips and shoulders — the same chain as a tennis forehand or a hook punch. Chasing a knockout means rotating harder and committing more of your body each time, and the whole room will be watching.
Slap-off with up to 8 friends
Open a match, share the code, and everyone faces the identical lineup of opponents — then takes their five strikes at their own pace. Live totals tick up for every player, and the heaviest hand in the arena wins. No console, no install.
Free to play in your browser — no download, no equipment
Slap Derby runs entirely in the browser on a laptop or desktop with a webcam. There is nothing to download, no account required to start, and no equipment beyond room to swing an arm. No camera? Swipe across the face with your mouse or finger instead. It is completely free to play.