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Image Diff

Compare two images pixel by pixel with split, slider, fade, highlight, and mask views, a match threshold, and an exportable difference mask.

Local processing

Processing details

Tool inputs are processed on your device.

Resources may be downloaded to run this tool. Account services are separate.

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Task path / input to outcome

How to compare two images

  1. 01

    Choose the two images

    Pick the Original and the Changed image — PNG, JPEG, or WebP, up to 12 MiB each, 8,192 pixels per side, and 8 million pixels for the precise comparison. JPEG files are normalized to their EXIF orientation on load, both sides show their format, dimensions, and file size, and Swap sides exchanges them in one click.

  2. 02

    Read the verdict

    Images with matching dimensions compare automatically in a Worker. With threshold 0 and antialiased pixels included, a zero count can display Pixel-identical under this comparison algorithm. In other settings, zero means no counted differences under the current threshold and edge treatment. A positive result reports the counted pixels and percentage.

  3. 03

    Switch between the five views

    Split shows both images side by side with synchronized zoom and pan — scroll to zoom, drag to pan, and the buttons or arrow keys work without a mouse. Slider reveals the change through a keyboard-operable divider, Fade overlays one image on the other at adjustable opacity, Highlight marks the differing pixels over the original, and Difference mask shows them alone.

  4. 04

    Tune the threshold and antialiasing

    Threshold controls the comparison algorithm's sensitivity, from 0 to 0.5; zero is most sensitive but is not a promise of byte-for-byte RGBA equality. Ignore antialiased edges is on by default and can exclude edge differences. Changing either setting triggers a new comparison and cancels the old run.

  5. 05

    Export the mask

    Export mask PNG saves a transparent mask of differences counted under the current settings. Even a Pixel-identical verdict is about this browser's decoded comparison under pixelmatch, not identical file bytes or guaranteed equality of every hidden RGBA channel. Use Hash Checker if file-byte identity matters.

Tool facts

Processing
In your browser
Input leaves this device
Never
Retention
Nothing is stored
Price
Free

Your input stays in the browser.

Image Diff uses its verified local execution path and does not create a hidden input or output history.

Local execution

Runs inside the current browser tab.

No hidden processing

Active tool data never becomes a Toolars document record.

No account required

Use the core workflow without creating a profile. Favorites sync to your account after you sign in.

Immediate reset

Clear the tab and the active working data is gone.

What Image Diff actually does

A design revision came back and someone must confirm only the intended region changed; a UI regression suite has screenshots from two builds and the failing area hides somewhere in a long page; two exports from the same pipeline should be identical but the eye cannot prove it. Load both images — the comparison runs locally — and switch to Highlight to see the stray watermark glow red over the original, drag the Slider where a button shifted by two pixels, and export the mask to attach to the bug. When the screenshots have different dimensions, the workspace says Visual comparison only instead of inventing numbers, and the resize step stays with Image Resizer.

Common questions

Which image formats are supported?
PNG, JPEG, and WebP are supported, up to 12 MiB each, after signature checks. GIF, HEIC, SVG, and PDF are outside this comparison pipeline. Browser decoding and color handling can affect the pixels seen here; compare in the target environment when cross-browser consistency matters.
What happens when the images have different dimensions?
The workspace switches to Visual comparison only: Split, Slider, and Fade keep working so you can inspect both versions, but no pixel counts or percentages are reported, because a number computed against rescaled pixels would be a false verdict. Resize one side with Image Resizer first when you need the precise comparison.
What does the threshold change?
Threshold is pixelmatch's perceptual color-distance setting. At 0 it is most sensitive, but it does not simply count every raw channel change; ignored antialiasing can also exclude edge pixels. Raising it tolerates more color variation, including compression noise. Review the mask and settings before treating a zero count as proof.
Does pixel-identical mean the files are identical?
No. Pixel-identical is shown only for a zero count with threshold 0 and antialiased pixels included. It is still a verdict from pixelmatch on pixels decoded by this browser, not a byte-level file comparison or a promise that every transparent pixel's hidden RGB channels match. Use file hashes for byte identity.
Are colors compared exactly?
The browser supplies decoded pixels to pixelmatch, and browser color handling can vary. Pixelmatch applies its perceptual distance and antialiasing rules rather than testing every RGBA channel for literal equality. Alpha affects the comparison, but hidden RGB under full transparency may not affect the verdict; this is not a print color proof.
Are my images uploaded anywhere?
No. Both files stay in the current browser tab, decoding and the pixel comparison run in an isolated local Worker, nothing is sent or retained, and no account is required.

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