How to compare two screenshots and find what changed
The short answer
For pixel-level changes, put one screenshot over the other in an image editor and set the top layer's blend mode to Difference: everything identical turns black, and what changed lights up. To know what changed in words — which value, label or element — ScreenFeel's Compare lens takes two captures and lists every difference, most important first, quoting old and new values while ignoring noise such as cursor position and compression.
Two kinds of difference
A pixel diff answers “did anything change?”. It is exact and catches a one-pixel shift, but it also flags the clock that ticked and the cursor that moved, and it never tells you what a change means. A meaning diff answers “what changed?”: the total went from 1,240 to 1,310, the Save button moved to the left, a row is missing. Most real questions are the second kind.
A pixel diff in a free image editor
- Open both screenshots in an editor with layers and blend modes — GIMP and Paint.NET are free.
- Put the newer screenshot as a layer on top of the older one, aligned at the top-left corner.
- Set the top layer's blend mode to Difference. Identical pixels turn black; anything that changed shows up bright.
- Zoom in on the bright areas to see what they are.
This only works when both screenshots have the same size and position. A capture that is a few pixels off makes everything light up.
What changed, in words: ScreenFeel's Compare
- Open the Library and tick two captures — the older one is used as the baseline.
- Choose Compare.
- Read the verdict: one sentence with the most important difference, then up to eight changes, each naming the element, where it sits and how it differs, with old and new values quoted where both are visible, plus anything that exists in only one of the two.
The Compare lens ignores anti-aliasing, compression artifacts, cursor and scrollbar positions and timestamps that merely ticked forward. The verdict is saved onto the newer capture, and you can keep asking questions about both images underneath it.
Where it saves the most time
- Regression checks after a release: the same screen before and after.
- Design reviews: two versions of a mockup, with every change listed.
- Dashboards and spreadsheets: this week against last week, with the numbers that moved.
- Proving a fix landed: the error screen before, the working screen after.
Questions people also ask
How do I find the differences between two images for free?
Layer them in GIMP or Paint.NET and set the top layer's blend mode to Difference; changed pixels light up. For a written list of what changed, ScreenFeel's Compare lens runs on its free monthly AI allowance.
Do the two screenshots need to be the same size?
For a pixel diff, yes. ScreenFeel's Compare reads both images for meaning, so they do not need to line up, although capturing the same area both times gives the clearest result.
Can it compare more than two screenshots?
Compare takes exactly two. For a series of screens, ScreenFeel's Make a guide lens reads two to eight captures in order and describes each step.