Observation method
Record the zoom with the screenshot
A layout screenshot is incomplete until the note names the viewport, the zoom, and the text size that produced it.
Two screenshots of the same page can disagree because the browser zoom changed. This guide adds three fields to every layout note so a later reader can repeat the view.
Write the three fields before you save the image
Record the CSS viewport width and height, the browser zoom percent, and the root text size if you changed it. A screenshot without those fields cannot be compared with the next one.
A fictional note says: viewport 1280 by 800, zoom 100 percent, root text 16 pixels. The next note says the same viewport at 200 percent zoom. Those are different observations.
Sources: W3C: Understanding Resize Text
Say what the picture is allowed to claim
The picture shows the page at that size and zoom. It does not show every phone, every browser, or text at 200 percent unless you captured that case.
If text overlaps or a control leaves the viewport, write the control name and the field values. Do not write the layout is broken with no size attached.
Sources: W3C: Understanding Resize Text
Keep the first capture when you retest
A fix needs the same viewport and zoom as the first note. Changing the window and then calling the problem gone does not retest the original view.
Store the first image, the three fields, and the later image together. The comparison is the record.