Here's a poor-man's perceptual diff: Cross your eyes.<p>I'm serious. Try opening this image: <a href="https://assets.contents.io/asset_rIfFTtwp.png" rel="nofollow">https://assets.contents.io/asset_rIfFTtwp.png</a><p>You see two images side by side. Now slowly cross your eyes, so that the two images merge into three images. Once they align, the new <i>middle</i> image will have information from <i>both</i> your left and right eyes, and your brain's perceptual system will automatically try to reconcile any differences.<p>You'll see the differences as shimmering portions of the image, that tend to be shifted forward or backward in 3D space. In this example, the text at the bottom is shifted rightward in the right image, which your brain interprets as "closer to the eye". Differences jump out!<p>You can use this trick any time you want to diff two screens, pieces of text, whatever! You don't need a diff program -- your brain's perceptual system already has one built-in.
We are using Percy [1] for this and are extremely happy with this. Almost zero effort to set up, just some time to get random data out of our tests to have stable visual output.<p>[1]: <a href="https://percy.io" rel="nofollow">https://percy.io</a>