Free image comparison tool
Compare two images online
Compare pictures, photos or screenshots for free, right in your browser. Your images never leave your device.
Paste works too: Cmd+V or Ctrl+V fills the next empty slot.
How does the image comparison work?
The tool compares the two images pixel by pixel, with anti-aliasing detection, then groups the changed pixels into areas. It is a pixel comparison, not AI and not a perceptual similarity score.
- 1
Load two images
Drop, paste or pick a Before and an After: two screenshots, two photos, or two exports of a design. Your browser reads them straight from your device and decodes them in a background thread, so the page stays responsive.
- 2
Compare every pixel
pixelmatch, an open-source pixel diff library, measures the colour difference of each pixel pair and skips the pixels it detects as anti-aliasing, the edge smoothing that varies between renders.
- 3
Group the changes
Changed pixels that sit close together are grouped into numbered areas, and each area gets a zoomed before and after crop, so you see what changed rather than a speckled mask.
Comparing screenshots after every UI change?
Checking two screenshots by hand works once. After every change to your UI it becomes a chore, and it is the chore UI Verify automates. UI Verify is visual testing for coding agents: your agent sees every UI change it makes, so visual bugs never reach production. It works with Playwright, Storybook, Vitest and Bun, and it is free for 10,000 snapshots a month, and 50,000 for open-source projects.
Image comparison, answered
- Are my images uploaded?
- No. The comparison runs entirely in your browser: both images are decoded and compared on your own device, in a background thread of this page, and are never sent to a server.
- Can I compare two photos or pictures?
- Yes. Any two pictures work: photos, screenshots, design exports or scans. Because the comparison is pixel by pixel, it is most useful when both pictures show the same scene at the same size, such as a photo before and after an edit. Two photos of the same subject taken from slightly different angles will show almost every pixel as changed; the Slider and Side by side views are the better way to compare those.
- What image formats can I compare?
- Any image your browser can decode: PNG, JPG and WebP, and the first frame of a GIF. Each image can be up to 25 megapixels, about 6000 by 4000 pixels.
- Can I compare images of different sizes?
- Yes. The two images are aligned at their top-left corners on a canvas as large as the bigger one, and the area only one image covers counts as changed. The result names both sizes. That shared canvas has the same 25 megapixel limit, so a very wide image and a very tall one may be refused together. For the cleanest comparison, export both images at the same size first.
- What does the sensitivity setting do?
- Sensitivity sets how different two pixels' colours must be before they count as changed. It maps onto pixelmatch's threshold: the default of 80 is pixelmatch's standard threshold of 0.1, 100 counts any colour difference at all, and lower values ignore small colour shifts such as compression noise.
- What is anti-aliasing, and why ignore it?
- Anti-aliasing is the blend of colours a renderer draws along the edges of text and shapes so they look smooth. The same screen rendered twice can smooth its edges slightly differently, which is noise rather than a real change. With Ignore anti-aliasing on, pixels detected as anti-aliasing are not counted; turn it off to count every pixel.
- Can it tell me how similar two images are?
- It tells you the share of pixels that are identical at the current sensitivity, for example 99.6% of pixels identical. That is a pixel count, not a perceptual similarity score like SSIM: it does not model how a person sees an image, so shifting a whole image by a few pixels can change most pixels while it looks almost the same.
- How do I compare screenshots automatically on every change?
- Use a visual regression testing tool, which captures your pages or components on every change and compares each one against an approved baseline. UI Verify does this for Playwright, Storybook, Vitest and Bun: your coding agent sees every UI change it makes, so visual bugs never reach production. It is free for 10,000 snapshots a month, and 50,000 for open-source projects.