Compare two images

Frequently asked questions

Are my pictures uploaded?

No. Both pictures are opened in your browser and stay in this tab's memory. The comparison, the difference map and the downloads are all made on your device. Only your view choices (the view, divider direction, tolerance and labels) are remembered, in this browser only.

What if the two pictures are different sizes?

The page tells you and lets you choose how B lines up with A: stretch B to A's size (right for the same photo saved at two sizes), fit B inside A keeping its shape, or show both at their actual pixel size, centred. When the shapes already match, B is stretched by default.

How does the difference map work?

Both pictures are laid on the same frame and compared pixel by pixel. A pixel counts as changed when its red, green, blue or transparency differs by more than the tolerance (0 to 255). Changed pixels are shown in a strong colour over a faded copy of A, or as the raw difference brightened four times. The page reports the share of pixels that changed and the area they cover. Very large pictures are compared at up to 12 megapixels.

Why does the difference show changes I can't see?

Saving a JPG or WebP changes many pixels slightly, and resizing does too. Raise the tolerance to ignore small changes like these; 16 is a good start for photos, 0 finds every single changed value.

Which formats can I open?

Anything your browser can show: PNG, JPG, WebP, GIF, BMP and SVG everywhere, and AVIF in current browsers. HEIC photos from iPhones and TIFF files need converting first; the page links to the converter. Phone photos are shown the right way up.

Can I download the comparison?

Yes, as PNG: the two pictures side by side or stacked, one picture split at the divider, or the difference map with the changed area boxed. Labels such as Before and After can be written on the picture. Very large results are scaled to stay under 16 megapixels so every browser can make them.

How do I zoom and move around?

Pinch on a touch screen or trackpad, hold Ctrl (or ⌘) and scroll, or use the + and − buttons. Drag to move when zoomed in, and double-click to jump to 100% at that spot. Every view keeps the same zoom and position, so you can switch views without losing your place.