PostureCheck is a webcam posture checker that runs in your browser. You sit up straight for a few seconds, it learns that posture, and then it tells you when you drift away from it.
The pose model
Each camera frame goes through Google's MediaPipe Pose Landmarker, a small model that finds 33 points on the body, including the nose, ears and shoulders. The model, and the WebAssembly runtime that runs it, are files served from this site and executed on your computer, using your graphics chip when the browser allows. No frame is sent anywhere.
What it measures
A front-facing camera can't see your spine, so PostureCheck measures five things it can see reliably, all relative to the width of your shoulders so that moving closer or further away doesn't throw it off:
- Head height: how far your ears sit above your shoulders. It drops when you slump or your head moves forward and down.
- Head size: the distance between your ears compared with your shoulder width. It grows when your head moves toward the screen ahead of your body.
- Shoulder level: the angle of the line between your shoulders.
- Seat height: how far your shoulders sink in the frame as you slide down the chair.
- Lean: how much bigger your whole upper body gets as you lean in.
Each is compared with your own calibrated baseline, combined into a score from 0 to 100 and smoothed so one noisy frame doesn't flip the result. Below the slouching line for longer than your alert delay, you hear a chime.
What it can't do
It can't see your lower back or your hips from the front, and it isn't a medical device. It doesn't diagnose anything. It's a habit tool: it notices the moment your posture slips, which is the moment you stop noticing it yourself.
Who built it
Mark Fulton is a leading AI agent and app developer, with 27 years in web development and 4 years building AI agents. He is the founder of Reinventing.AI and the Agent Ops Club, and he founded Vibe Coding is Life, a Facebook community of 340,000+ members. He built PostureCheck, a posture checker that runs entirely in the browser, so no video ever leaves your computer. More about Mark.