Compare Images
Compare two images and see exactly what changed: a slider, the differing pixels highlighted and the changed areas boxed.
By Syed Mubashir Ali · Last updated
Which view to use
| View | Shows | Best for |
|---|---|---|
| Slider | Both images in one frame; drag to reveal one or the other | Seeing a change in context: a moved element, a recoloured area |
| Side by side | The two images next to each other, changed areas boxed on both | Comparing layouts and reading text in both versions |
| Difference | Changed pixels in red over a faded copy of the original | Finding every change, however small, at a glance |
| Fade | One image blended into the other, with a slider for how much | Spotting shifts and misalignments, which show as ghosting |
Tolerance, JPEGs and images of different sizes
A PNG screenshot saved twice is identical pixel for pixel, so 0% tolerance is right for screenshots and exported graphics: any red is a real change. A JPEG is different: every save adds faint noise, so two copies of the same photo differ slightly almost everywhere. In our tests, a photo saved again at a similar JPEG quality had more than half its pixels marked at 0% and a fraction of a percent at the starting 10%. Raise it further if a heavily compressed or resized photo still shows scattered red.
Two versions of the same picture at different resolutions, such as a 2× screenshot and a 1× one, are both compared at the smaller size. Images of different shapes are lined up at their top-left corners, the way a page and a slightly taller version of it line up, and anything only one image covers counts as different. Images over 12 megapixels are compared scaled down so the page stays responsive; a note under the result says when either happens.
- Image Resizer: resize one image to match the other before comparing.
- Image Cropper: crop both to the same area to compare just one part.
- HEIC to JPG: convert iPhone HEIC photos your browser can't open.
How to Use Compare Images
- 1Drop the original image on the left and the changed one on the right, or paste a screenshot with Ctrl+V (⌘+V on a Mac). Swap them if they're the wrong way round.
- 2Read the summary: what share of the pixels differ and in how many areas. The changed areas are boxed in red.
- 3Switch views: Slider to drag across both, Side by side, Difference for every changed pixel in red over a faded copy, or Fade to blend one into the other.
- 4Set the tolerance: 0% counts every pixel that isn't identical, which suits screenshots and PNGs; the starting 10% ignores the faint noise a JPEG photo picks up each time it's saved. Tick Actual size to check pixels at 100%.
- 5Download the difference image for a bug report or a design review, or press Full screen to give the comparison the whole window.
Frequently Asked Questions
How do I compare two images?
Drop the original image on the left and the changed one on the right, or paste a screenshot. The comparison appears straight away: drag the slider across both, or switch to Side by side, Difference or Fade. Changed areas are boxed in red, and the summary says what share of the pixels differ.
What counts as a difference?
Every pixel is compared, its colour and its transparency. Tolerance sets how big a difference has to be to count: at 0% any pixel that isn't identical counts, which suits screenshots and PNGs; the starting 10% ignores the faint noise a JPEG photo picks up each time it's saved; higher values ignore slight colour shifts too.
Can I compare images of different sizes?
Yes. Two versions of the same picture at different resolutions are both compared at the smaller size. Images of different shapes are lined up at their top-left corners, and areas only one of them covers count as different. A note under the result says which was done.
Are my images uploaded?
No. Both images are opened, drawn and compared in your browser, and nothing is sent to a server, so confidential screenshots and unreleased designs are safe to compare here. Closing the tab clears them.
Which image formats work?
PNG, JPG, WebP, GIF (its first frame), BMP, AVIF and SVG: anything your browser can show. iPhone HEIC photos open in Safari; in other browsers, convert them with HEIC to JPG first. Images over 12 megapixels are compared scaled down, and a note says so.
Can I save the differences?
Yes. Download difference image saves a PNG with the changed pixels in red over a faded copy of the original and the changed areas boxed, ready for a bug report or a design review.
Can it compare PDFs or text?
Not here. For PDFs, Compare PDF lists every word added or removed and boxes the changed areas on each page. For text and code, use the Diff Checker.
About Compare Images
Two screenshots that look the same aren't always the same. A button moved four pixels, a price changed in a banner, a logo was exported in a slightly different blue: the eye skims past it, and the release goes out wrong. Compare Images checks every pixel of two images and shows you exactly where they differ, boxed in red, so a change you'd miss by eye can't hide.
It's for anyone who checks one image against another: developers and testers comparing a page before and after a change, designers checking an export against the approved mock-up, photographers comparing two edits, and anyone playing spot the difference with a contract scan or a product photo. The slider and the fade show the change in context; the Difference view shows every changed pixel in red, so nothing has to be found by staring.
Both images are opened and compared in your browser, with no upload and no account, so unreleased designs and confidential screenshots stay on your device. The only file that leaves the page is the difference image you choose to download.