Image Comparison Tool
Upload an image to compare original vs converted quality side by side.
Click to upload or drag and drop
HEIC, WEBP, AVIF, TIFF, BMP, SVG, GIF, PNG, JPG, CR2, NEF, ARW, DNG
Quality Metrics
Image A (original)
Image B (converted)
Quality Comparison Results
Quality Metrics
Keyboard Shortcuts
General
More tools
- Convert HEIC, RAW, AVIF to anything.
- Compress Smaller file, same look.
- Resize Percent, pixels or preset.
- Crop Snaps to faces for you.
- Edit Rotate, filter, enhance.
- Remove BG One click, no green screen.
- Video Clips, frames and GIFs.
- Bulk Up to 50 images at once.
- Annotate Arrows, boxes, blur and text.
- Inspect Read EXIF and metadata.
- Identify Detect format by magic bytes.
- Metadata Write EXIF, GPS, copyright.
How the quality comparison works
KoalaPic compares two images and reports how different they actually are, using SSIM and PSNR rather than an opinion. SSIM scores structural similarity from 0 to 1: at or above 0.98 the difference is rated excellent and is invisible in normal viewing, 0.95 is good, 0.92 is acceptable, and below that the compression is showing. The slider puts the two images side by side so you can check the score against your own eyes.
What the numbers mean
- SSIM measures structure, which is what human vision notices first; it is computed on the grayscale version of both images.
- PSNR measures raw pixel error in decibels — useful for spotting a large regression, less reliable for judging perceived quality.
- The report also gives both file sizes and the percentage saved, so quality can be weighed against bandwidth.
- The same thresholds drive smart quality mode, which searches for the lowest quality setting that still meets the SSIM target you pick.
What is a good SSIM score for a compressed image?
0.98 and above is where the difference stops being visible in normal viewing, which is why KoalaPic rates it excellent. 0.95 to 0.98 is good enough for most web use, 0.92 to 0.95 is acceptable when file size matters more than fidelity, and below 0.92 compression artefacts are usually noticeable.
What is the difference between SSIM and PSNR?
PSNR measures how far each pixel moved, in decibels; SSIM measures whether the structure a viewer perceives survived. Two images can share a PSNR and look very different, which is why SSIM is the score KoalaPic rates quality on and PSNR is reported alongside it.
How do I tell whether compression went too far?
Compare the compressed file against the original: if SSIM is at or above 0.95 the result is safe for web use, and if it falls below 0.92 raise the quality setting. Flat colour, text and sharp edges degrade earliest, so check those regions with the slider rather than a photograph of foliage.