Compare Images
Compare two images with a slider
Image 1 (before)
Image 2 (after)
About Compare Images
Compare Images puts two pictures on top of each other so you can see what changed between a before and an after version: a retouch, an export setting, a new screenshot. In the Slider view, a vertical line splits the frame and the Slider control below moves it. In the Differences view, every pixel whose red, green, blue, or alpha value differs by more than 16 out of 255 is painted red over a faded copy of the first image, with the count and percentage of changed pixels; that picture can be downloaded as a PNG. Both images stay in your browser.
How to compare two images
- 1Click "Image 1 (before)" and choose the original picture.
- 2Click "Image 2 (after)" and choose the edited one.
- 3In the "Slider" view, move the "Slider" control to sweep the dividing line across both pictures.
- 4Click "Differences" to paint the changed pixels red, then click "Download" to save differences.png if you need it.
Formats and limits
- Input formats
- Two pictures the browser can open, such as JPG, PNG, WebP, or GIF
- Largest image
- 100 MP per image; a larger one is refused with a message
- Changed pixel
- A difference above 16/255 on red, green, blue, or alpha
- Different sizes
- Image 2 is scaled to the size of image 1 before comparing, and the summary says so
- Download
- differences.png, at the size of image 1
Where your image is processed
Both pictures are read and compared by this page inside your browser, and neither is uploaded. The difference image is built in the tab and is gone once you close it, unless you saved it. The cleaned text of an error message, if any is shown, goes to us with the name of this tool and of your browser, plus its version, but never the images.
Frequently asked questions
Can I compare images of different sizes?
Yes. Image 2 is scaled to the width and height of image 1 before the pixels are compared, and the summary under the Differences view gives both sizes so you know it happened.
Can I drag the line on the image?
No. The dividing line follows the "Slider" control under the pictures, from 0 to 100 percent of the width; the line itself cannot be grabbed. On a touch screen, slide that control with your finger.
What counts as a changed pixel?
16 out of 255 is the threshold: a pixel counts as changed when its red, green, blue, or transparency value differs by more than that. Smaller shifts are drawn in faded gray, not red, and are not counted.
Can I compare more than two images?
No. The page holds one before and one after picture. To check a whole folder for copies, use Duplicate Image Finder, which compares every pair in a batch.
Tips and tricks
- ✓Load the same file in both boxes to see the identical-images message, then swap in the edited version.
- ✓After compressing a photo with Compress Image, use Differences to see where the picture changed.