Image Comparison

Image mode focuses on visual differences between two images.

Start an Image Comparison

Drop two images to open image comparison.
If only one image is loaded, drop another image to begin comparing.

If you drop a new image while already comparing two images, ABDiff keeps the most recent image.

Compare Modes

Mode type	Purpose
Split, Side-by-side, Crossfade	Human-driven inspection
Change Boxes	Region-based change detection
Absolute, Proportional	Pixel-exact change detection
Blurred, Edge	Noise-tolerant structural checks
SSIM	Perceptual equivalence
Delta E	Perceptual color accuracy

Split View shows each image on one side of a draggable divider, ideal for visually checking layout, spacing, and alignment. Because it relies on human inspection, subtle pixel-level differences can be easy to miss.
Side-by-side shows the left image in the left pane and the right image in the right pane. It is useful when you want to inspect both images at the same time without an overlay.
Crossfade blends images with a slider to emphasize the left or right image.
Change Boxes detects changed regions and draws red rectangles on the right image only. It works best for already aligned screenshots or renders. If the images have different sizes, ABDiff compares only the shared top-left intersection and ignores everything outside that overlap.
Absolute Difference shows the exact per-pixel differences between images. It highlights every changed pixel, but can also surface noise from antialiasing or minor rendering variations.
Proportional Difference emphasizes relative pixel changes, which can make subtle differences in very dark or very light areas easier to see. Like Absolute Difference, it operates at the pixel level and may exaggerate insignificant changes.
Blurred Difference applies a light blur and downsample before comparing images. This reduces pixel-level noise and helps focus on larger, visually meaningful changes rather than minor raster differences.
Edge Difference compares the outlines and shapes in each image instead of their colors. This makes it well suited for detecting layout, spacing, or structural changes, but it does not highlight color differences.
SSIM compares images based on perceived visual structure rather than exact pixel values. It is useful for judging whether two images would appear the same to a human, even when small pixel-level differences are present.
Delta E (Lab) compares images using perceptual color distance in Lab color space. It highlights color changes that are noticeable to the human eye, making it especially useful when color accuracy matters.

Alignment

Alignment determines how the two images share a common pixel grid before comparison. It never changes zoom or view scale. Options:

None (Top-Left): keep both images at 1:1, anchored to the top-left.
Find Smaller Image in Larger…: locate the smaller image inside the larger one and align it.
Normalize Right to Left: rescale the right image to match the left image’s pixel grid.
Normalize Left to Right: rescale the left image to match the right image’s pixel grid.

When alignment is active, a badge appears in the header (for example, “Normalized to Left”).

Side-by-side and Change Boxes use the images as shown in each pane and do not apply alignment.

Loupe

The loupe provides localized magnification for pixel-level inspection without affecting the main viewport.

Toggle the Loupe using the scope icon in the image comparison toolbar.
The loupe tracks the cursor as a floating circular overlay.
The magnified content is sampled directly under the cursor.
The loupe is offset from the cursor so the inspected region remains visible.
In Change Boxes, the right-pane loupe includes the red box overlay by default. Hold D to inspect the raw right image without the overlay.

Shortcuts

Hold A to temporarily show the left source image inside the loupe.
Hold D to temporarily show the right source image inside the loupe.
Press S to cycle magnification: 1× → 2× → 4× → 8× → 1× (default: 4×).

Fit and Zoom

Fit the image using the settings button:

Actual Size (1:1): fixed 1:1 pixels. Never scales automatically.
Fill Window (Split, Cross-fade, and Difference modes): one-time fit to the current viewport. Can scale above 100%.
Fill Pane (Side-by-side and Change Boxes modes): one-time shared fit for both panes. Can scale above 100%.
Show Whole Image: one-time fit that keeps the entire image visible, but never scales above 100%.
Fit to Window (Auto): persistent auto-fit mode that recalculates as the window size changes.
- In Split/Cross-fade/Difference, it behaves like continuous Fill Window.
- In Side-by-side/Change Boxes, it automatically uses 1:1 when both images fit; otherwise it falls back to whole-image fit.

Show Whole Image vs Fit to Window (Auto)
Use Show Whole Image when you want a one-time, no-upscale fit.
Use Fit to Window (Auto) when you want ABDiff to keep adapting as you resize the window.

Zoom the image using the mouse wheel or the View ▸ Zoom command.

Reposition the image dragging it with the mouse or using the minimap. Repositioning is only available when the image dimensions exceed the current window.