What it does
Is the new screenshot the same as the old one? This page puts two images on top of each other so you can see the difference. Drag a line across to wipe between them, fade one over the other, or let it mark every pixel that changed and count them.
Your images are opened in this page only; nothing is uploaded. To shrink or resize an image first, use the image resizer; to compare two texts instead, try compare documents.
How to use it
- Choose image A (before) and image B (after). An example pair is shown until you do.
- Pick Slider, Overlay or Difference.
- In Slider, drag across the picture or move the slider. In Overlay, change the opacity. In Difference, read the percent changed.
- Download this view saves what you see as a PNG.
What each setting does
- Slider: A shows on the left of the line and B on the right.
- Overlay: B is drawn over A; 0% shows only A, 100% only B.
- Difference: pixels that changed are red; everything else is faded grey. The percent is changed pixels out of all pixels.
- Threshold: how much a pixel’s red, green, blue or transparency value (0 to 255) must change before it counts. 16 ignores tiny changes such as JPEG noise; 0 counts every change.
- Different sizes: B is scaled to A’s width and height, and a note says so. If the shapes differ, B is stretched, so the difference view shows extra change.
- Very large images are compared at up to 2,000 pixels on the longest side.
Worked example
The example is two 200 × 150 pictures of a house. In the second, one 10 × 10 square in the grass is dark blue. That is 100 changed pixels out of 200 × 150 = 30,000, so the difference view says 0.333% of pixels changed, and the square shows in red.
FAQs
Why does a re-saved JPEG show changes everywhere? JPEG compression shifts many pixels slightly. Raise the threshold to 20 or 30 to see only real edits.
Can I compare a photo with a cropped copy? Not well: the pixels no longer line up, so most of the picture shows as changed.
Does it work offline? Yes. Once the page has loaded it needs no internet.
Where the numbers come from
- Pixel-by-pixel comparison of red, green, blue and alpha values. fibub's own working.
Standard scientific values, such as constants, atomic weights and melting points, are facts found in every textbook; we name where ours were checked. If you are an author or publisher and want a value, a credit or a table changed or removed, tell us and we will act quickly.
Last updated 2026-11-10.