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Compare an Image Before and After Compression

Upload the original first and the compressed copy second to reveal small decoded-pixel changes with a sensitive comparison preset.

Compression reviewSensitive comparisonLocal processing
Image AOriginal
Image BModified

Upload both images to start comparing

JPEGPNGWebPGIFAVIFBMPHEICHEIF
Back to Compare Image Differences Online

See where compression changed the image

Lossy JPEG, WebP, AVIF, and other encoding steps can change decoded pixels even when the images look similar at first glance. This preset keeps noise filtering off and starts at the most sensitive available level.

The result reports thresholded pixel changes and a difference heatmap. It does not calculate PSNR, SSIM, Delta E, LPIPS, or an objective visual-quality score.

How to compare compression changes

  1. 1

    Add the original

    Select the uncompressed or higher-quality source image first.

  2. 2

    Add the compressed copy

    Select the version produced by your compressor or encoder second.

  3. 3

    Inspect the result

    Use the slider and heatmap, then adjust sensitivity if ordinary encoding noise overwhelms the useful changes.

Frequently asked questions

Does a highlighted pixel mean the compression is visibly bad?

Not necessarily. The tool detects decoded-pixel changes above a threshold; it does not model human perception.

Which file should I upload first?

Upload the original or higher-quality image first and the compressed output second.

Are the files processed locally?

Yes. Supported images are decoded and compared in your browser.

Related image tools

Before and After Comparison

Review two versions with a slider and highlighted pixel changes.

Image Difference Heatmap

Highlight changed pixels and download the difference map.

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