Image Comparison Tool — SSIM, PSNR & Pixel Heatmap
Upload any two images and DiffALL pinpoints every pixel-level difference. Structural similarity score, PSNR, colour histogram, and a heatmap overlay — all in seconds.
Try DiffALL free — no sign-up neededWhat DiffALL measures
Pixel Heatmap
JET-coloured overlay shows exactly where the two images differ — blue for identical, red for maximum difference.
SSIM Score
Industry-standard Structural Similarity Index, 0–100%. Accounts for luminance, contrast, and structure — closer to human perception than raw pixel diff.
PSNR
Peak Signal-to-Noise Ratio in dB. Standard benchmark for compression quality evaluation.
Histogram Similarity
Per-channel colour histogram correlation reveals tonal shifts even when pixel positions match.
Sharpness & Brightness
Laplacian variance for blur detection and mean luminance comparison for exposure differences.
Feature-Based Alignment
ORB keypoints + RANSAC homography aligns rotated or resized images before comparing — handles real-world photo pairs.
Supported formats
Use cases
Design QA
Catch unintended changes between design iterations before they ship.
Compression Testing
Measure quality loss when converting PNG to WebP or JPEG at different quality levels.
Visual Regression
Compare before/after screenshots to detect UI regressions in automated test pipelines.
Duplicate Detection
Identify near-duplicate images in large photo libraries using SSIM similarity scores.
Frequently asked questions
How do I compare two images and see the differences?
Upload your two images to DiffALL. It calculates SSIM, PSNR, and histogram similarity, then produces a colour heatmap showing exactly which pixels changed. No registration needed.
What is SSIM and what score is acceptable?
SSIM (Structural Similarity Index) ranges from 0 to 100%. Above 95% is excellent (differences are imperceptible), 80–95% is acceptable, below 80% means noticeable degradation.
Can DiffALL compare images of different sizes?
Yes. DiffALL resizes both images to a common resolution before comparison. For images taken from different angles or zoom levels, use Feature Mode which aligns them with a homography transform first.
What image formats are supported?
JPG, PNG, WebP, BMP, TIFF, and GIF. Files up to 20 MB each.
Is my image data stored on your servers?
Files are processed in memory and deleted within 2 hours. We do not store, share, or inspect your images.
Ready to compare images?
Free, no install, no sign-up required for your first comparison.
Start comparing now →