How motion detection works

The tool compares consecutive video frames pixel-by-pixel on an HTML5 canvas. When the difference between a pixel in the current frame and the same pixel in the previous frame exceeds the sensitivity threshold, it is marked as motion. Areas of detected movement are highlighted with a red overlay.

Tips to reduce false positives

Use consistent lighting - flickering lights or sunlight changes trigger false positives.
Raise the sensitivity threshold if camera noise triggers detections with no movement.

Your camera feed never leaves your device

All frame comparison is performed locally on the canvas. No video is recorded, stored, or transmitted to any server.

Sensitivity tuning guide

The threshold slider controls how large a per-pixel difference must be before it counts as motion. A lower threshold detects subtle movements (slight shadows, small animals) but also triggers on camera noise. A higher threshold only detects larger, more definitive movements.

Indoor, controlled light: use a lower threshold (more sensitive) since the background is stable.
Outdoor / variable light: use a higher threshold to avoid false triggers from wind-moved leaves, clouds changing brightness, or passing car headlights.

Frame difference algorithm

The basic motion detection algorithm computes:

|pixel_current − pixel_previous| > threshold -> mark as motion

More advanced approaches use a background model (a running average of many recent frames) instead of just the previous frame. Background modeling is more robust to gradual lighting changes but requires more computation. This tool uses the simpler frame-difference method, which is fast enough to run in real time in a browser.

Use cases

Baby monitor: detect when a baby starts moving or wakes up.
Security / door detection: trigger an alert when someone enters a room or approaches a door.
Wildlife camera: capture still frames when animals pass through the camera field.
Desk detection: detect whether a chair or desk is occupied - useful for "at-desk" presence indicators.
Art / creative: use motion data to trigger visual effects or interactive installations.