Are my screenshots uploaded?

No. Decoding, comparison and PNG generation run in a Web Worker in your browser. Images, pixels and reports are not sent to a server.

How are similarity and mismatch calculated?

Mismatch is changed pixels divided by compared pixels × 100, and similarity is 100 minus mismatch. Ignored regions are removed from both counts. It is a pixel metric, not a perceptual one.

How do I stop timestamps or ads from failing the comparison?

Add ignore regions in Advanced settings, or select a detected changed region and choose Ignore this region. Ignored pixels are excluded from every metric, the region list and both exports.

Image Diff Checker

Runs locally in your browser

Compare screenshots and inspect visual regressions pixel by pixel

Choose two images or load the example.

Input

Baseline

Drop PNG, JPEG or WebP here

PNG, JPEG or WebP · up to 50 MB · or paste an image

Current

Drop PNG, JPEG or WebP here

PNG, JPEG or WebP · up to 50 MB · or paste an image

Advanced settings

Pixel threshold

Lower values detect smaller color differences.

Include anti-aliased edges

Enable to count edge differences identified by pixelmatch.

Transparent pixels

Alignment

Comparison crop

Ignore regions (0)

Result

Choose two images or load the example.

PDF Diff CheckerCompare PDF text, pages, and visual changes locally Screenshot Image AnnotatorHighlight, explain, redact, and present screenshots Code Diff CheckerCompare code/text side-by-side

Compare local screenshots

Load baseline and current PNG, JPEG or WebP images. Compare six synchronized views, align, crop and exclude dynamic areas. Select a region to focus it. Download the exact displayed diff or heatmap, or copy a Markdown report.

Alignment, crop and ignore regions

Top-left places both images at the origin; Center centers each image on the larger canvas; Manual shifts Current by an X/Y offset to correct small position changes. Crop limits the comparison to one rectangle. Ignore regions exclude timestamps, avatars, ads or counters from the diff and from every metric. Transparent pixel handling decides whether hidden RGB behind fully transparent pixels counts.

How metrics work

pixelmatch classifies changes with the selected threshold and edge tolerance. Alpha and transparent RGB follow the selected policy. Changed pixels separated by at most 4 unchanged pixels in any of the eight directions form one region. Mismatch = changed ÷ compared × 100; similarity = 100 − mismatch. The union of ignore regions is removed from the denominator; with no compared pixels, percentages are unavailable. This is pixel similarity, not a perceptual metric.

Privacy and limits

Decode, comparison and PNG generation run in a cancellable browser Worker. Files, pixels, dimensions and reports are never uploaded or sent to analytics. Limits: 50 MB per file and 4 million pixels per image or comparison canvas. Alignment, crop and exclusions share comparison-canvas coordinates.