WinMerge's Image Compare mode is a newer addition that lets you visually compare two images and highlight pixel-level differences — incredibly useful for UI testing, design reviews, and quality assurance.
Supported Image Formats
WinMerge Image Compare supports: PNG, JPG/JPEG, BMP, GIF, TIFF, and WebP files.
How to Open an Image Comparison
- Open WinMerge and go to File → Open
- Browse to your first image in the left field
- Browse to your second image in the right field
- Click OK — WinMerge auto-detects the file type and opens Image Compare mode
Difference Highlighting Modes
- Side by Side — shows both images next to each other
- Overlay (XOR) — overlays the images to show differences as bright pixels
- Overlay (Alpha) — blends both images with adjustable opacity
- Block Highlight — draws colored rectangles around areas that differ
💡 Tip: Use the Zoom slider to examine small pixel-level differences more closely. Very useful when comparing UI screenshots with minor layout shifts.
Practical Use Cases
- Compare UI screenshots before and after a CSS change
- Verify that a design export matches the mockup
- Check that image compression did not degrade quality
- QA testing: confirm that generated images are identical across builds