Compare two images

To compare two images, this tool shows exactly where they differ: pixel by pixel, with red marks, frames around the changed areas and a percentage. Choose two images, set the tolerance and you are done, all in your browser with nothing uploaded.

Source: Wikipedia – Image differencing (change detection). Updated: 2 October 2026.

How it is calculated

In short: the tool lays two images on top of each other and checks every pixel: if one of the colours (red, green, blue) or the transparency differs by more than the tolerance, the pixel counts as changed. From this come the percentage, red marks and frames around connected change areas.

How it works

Drop two images, choose them or paste with Ctrl + V. The first is image A, the second image B.
Pick a view: highlight differences, blend with slider or difference image.
Use the tolerance to hide noise: in photos saved as JPG, tiny deviations are normal.
If needed, save the comparison image as PNG.

The views

Highlight differences: image A greyed out, changed pixels red, yellow frames around the areas. Good for spot-the-difference puzzles and screenshots.
Blend: image B lies over image A; the slider moves the boundary. You see small shifts this way.
Difference image: the brighter a pixel, the larger the deviation. Identical spots stay black.

Honest limits

The comparison is pixel by pixel. An image shifted by one pixel counts as changed everywhere; it is unsuitable for layout or photo comparisons with rotation.
If the images differ in size, image B is stretched to the size of image A. With different aspect ratios the tool warns you.
For the comparison very large images are reduced to 8 megapixels, so the tiniest differences can disappear.

Privacy

The images are processed only in your browser and are not uploaded.

Frequently asked questions

How can I compare two images and find the differences?

Choose both images and keep the “Highlight differences” view. Changed spots appear red and yellow frames show connected areas. The percentage gives the share of differing pixels.

What does the tolerance do?

Differences up to this value are not counted. This hides noise created when saving as JPG. With 0 you see every difference, however small.

What does the difference image show?

For each pixel the size of the difference, amplified four times. Black means identical, bright spots are changed.

Does the comparison work for images of different sizes?

Yes, image B is stretched to the size of image A. With a different aspect ratio a note appears, because the result is then of limited use.

How do I find the mistakes in a spot-the-difference puzzle?

Load both versions and choose “Highlight differences”: the yellow frames show every area where something has changed.

Are my images uploaded?

No. The comparison runs entirely in your browser; the images never leave your device.

Sources and legal basis

As of: 2 October 2026 · Editorial policy