Before & After Image Comparison
Blink Test, Split Wipe & Pixel Diff

How to compare before and after images

The simplest workflow takes about 30 seconds. Open the tool, drop your "before" image into the anchor zone on the left panel, then drag your "after" image into the states area. The tool immediately displays your anchor image on the canvas. Click on your state to activate it, then switch between comparison modes using the toolbar.

For blink comparison, hit the play button. The tool will rapidly alternate between your before and after images. You can adjust the blink speed — faster intervals (200ms) are best for catching any change at all, while slower intervals (1–2 seconds) give you more time to examine each version. This technique leverages how the human visual system detects change through motion — the same principle astronomers used to discover moving objects in the night sky.

For split wipe, drag the divider across the image. This is ideal when you want to inspect a specific region — checking whether a background replacement has a clean edge, or whether a color grade transitions smoothly across a face.

For pixel diff, the tool generates a heatmap overlay. Bright areas indicate significant change; dark areas indicate no change. This is particularly useful for quality assurance — confirming that an edit only affected the intended region, or checking whether a file conversion introduced compression artifacts.

Comparing more than two images

Unlike standard before/after slider tools that are limited to two images, you can add up to 50 states. This is useful for comparing multiple editing approaches, different filter presets, or a series of revision rounds. The blink mode cycles through all enabled states, so you can quickly scan across many versions to find the best one.

Exporting your comparison

Once you've settled on your final version, you have several export options. Export a single frame as PNG. Create an animated comparison as a GIF or MP4 — useful for portfolio posts or client presentations. Or switch to Scene mode to build a styled comparison layout with both images side by side, layered, or arranged in a custom composition.

Compare Lightroom presets — what the backslash key can't do

Lightroom's built-in before/after toggle (the backslash key) shows your original RAW against your current edit. Useful — but it only has one "before." There's no built-in way to compare two different presets applied to the same image, two different edit directions, or two export settings side by side.

The workflow: apply Preset A, export as a high-quality JPEG. Switch to Preset B, export. Open both in Compix — anchor one, add the other as a state. Blink at 300ms. The better preset becomes obvious in under ten seconds — not because you're analyzing it, but because your visual system registers the stronger image directly. No toggling. No memory required.

The same method works for comparing Capture One styles, checking whether a specific edit decision (warmer shadows, lifted blacks, a different clarity amount) actually improved the image, or comparing two export quality settings for file size versus visual quality tradeoffs. See also: retouching QA tool for professional pre-delivery checks →

Comparing client images safely

If you're comparing edits on client portraits, wedding photos, or event coverage, the comparison tool you use matters. Compix processes everything locally — your client's images never leave your machine. The tool also works fully offline as a PWA, which means you can use it on location, in a client review session, or anywhere without internet. See also: pixel diff heatmap for technical verification →