Image difference checker

What it does

Highlight changed pixels between two screenshots and measure the percentage changed.

How to use it

1. Choose a before and after JPEG, PNG or WebP, up to 20 MB and 16 megapixels each.
2. Set tolerance from 0 to 255. Zero reports any displayed channel difference; 255 reports none.
3. Download the difference PNG and a JSON report. Images stay on your device.

Example

Comparing two 100 × 100 images with one changed pixel gives 0.01% changed at zero tolerance.

Methodology

Canvas decodes both images at original size. RGB channels composited over white are compared; a pixel changes when any channel difference exceeds the chosen tolerance. Changed pixels are pink.

Limitations

Equal dimensions required. No alignment, perceptual similarity or semantic comparison. Compression, antialiasing and colour management can change pixels. Fully transparent RGB is ignored.

Automation

This tool runs in your browser. No upload API or MCP endpoint is available.