What is the difference between Pixel-by-Pixel and Perceptual comparison?

Pixel-by-Pixel comparison checks the exact RGB value of every coordinate; any change, no matter how small, is flagged. Perceptual comparison uses algorithms to ignore changes that the human eye cannot perceive, such as minor compression noise or anti-aliasing.

Does the tool support transparent backgrounds?

Yes, the tool supports RGBA channels. You can choose to include the alpha channel in the comparison or ignore transparency to focus solely on the visible color changes.

How does the 'Threshold' setting work?

The threshold defines the maximum allowable difference between two pixels before they are marked as 'different'. A threshold of 0 requires an exact match, while higher values allow for slight color variations.

Are my uploaded images stored on your servers?

No. The tool uses a zero-persistence architecture. Images are processed in memory and deleted immediately after the session ends, or processed entirely on the client side via WebAssembly.

Can I compare images of different sizes?

Yes. The tool includes an automatic alignment and scaling feature that can either pad the smaller image or scale both to a common denominator to allow for a meaningful comparison.

What is a 'Diff-Overlay'?

A Diff-Overlay is a generated image where the similarities are faded and the differences are highlighted in a vibrant color, making it easy to see exactly where the two images diverge.

Image Comparison Tool

Online Image Compare Tool

The Image Compare Tool lets you drag a slider between two images to reveal differences in real-time. Upload a before/after pair of photos, design iterations, or any two images to visually compare them side-by-side. All processing happens locally in your browser — your images are never uploaded.

How to Compare Two Images Online

Upload the first image (original or "before") to the left panel
Upload the second image (edited or "after") to the right panel
Drag the slider left and right to reveal differences between the images

Use Cases for Image Comparison

Photo editing before/after — compare original and retouched versions
Design diffs — spot differences between UI mockups or screenshots
Compression quality check — compare original vs. compressed image
A/B visual testing — compare two graphic design variants
Web screenshot diffs — compare before/after a CSS change

Frequently Asked Questions

How do I compare two images online?

Upload both images and drag the slider to reveal differences. No account, no upload to server — everything runs in your browser.

Do the images need to be the same size?

No, but same-size images give the best comparison accuracy. Different sizes can be compared but the slider may reveal misaligned areas.

Is my image data private?

Yes. Images are loaded directly in your browser and never sent to any server. All comparison rendering is done locally.

Related Tools

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GIF to MP4 - Free online gif to mp4 tool.

Image Comparison Tool – DataMorph