You will need to install a user script manager extension to install this script.
Creates hover tooltip popup text bubble (
title attribute) from
src attributes of image elements on page.
(Illustration clip from https://slate.com/human-interest/2021/02/stop-defacing-quotes-with-brackets.html)
To make the title tooltip text appear, place your cursor over element stop moving the cursor for about half a second.
This (Greasyfork.org) page does not add alt attribute for screenshots (below), so with this script installed you should see "⚠ Alt missing" in it's tooltip.