FastImageToolsFastImageTools

Generate an Image Difference Heatmap

Compare two aligned images with the sensitive preset and export a PNG that emphasizes pixels changed beyond the threshold.

Downloadable PNGSensitive presetLocal processing
Image AOriginal
Image BModified

Upload both images to start comparing

JPEGPNGWebPGIFAVIFBMPHEICHEIF
Back to Compare Image Differences Online

Turn pixel changes into a visible map

The tool decodes both images, compares aligned RGBA pixels, and builds a heatmap from differences above the active tolerance. The sensitive preset starts with tolerance 2 and no noise, color, or transparency exclusions.

Use the result to locate changed regions in screenshots, edited assets, renders, or re-encoded images. It is a difference visualization, not a semantic similarity or perceptual-quality score.

How to create the heatmap

  1. 1

    Add the reference image

    Choose the baseline or original image first.

  2. 2

    Add the comparison image

    Choose the second version with matching dimensions and alignment.

  3. 3

    Download the map

    Review the overlay and verdict, then download the generated difference heatmap PNG.

Frequently asked questions

What does the heatmap show?

It emphasizes decoded pixels whose channel difference exceeds the selected sensitivity threshold.

Is this a semantic or AI heatmap?

No. It is calculated from aligned pixel differences and does not recognize objects, faces, or meaning.

What format is downloaded?

The generated difference heatmap is downloaded as a PNG image.

Related image tools

Before and After Comparison

Review two versions with a slider and highlighted pixel changes.

Compare Compression Results

Inspect pixel changes between an original and compressed image.

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