Do not post xkcd comics without also providing the alt-text.
If you live in Los Angeles (around 33°52'N, roughly the latitude of Hermosa Beach) the black hole in V404 Cygni passes over you each day. On Christmas Day it will be directly overhead around 2pm.
Tf is the alt text? I've only seen this on lemmy, and only the last week or so. Where does it come from, and how is it related to xkcd?
Got it, I've always called it the description.
Congratulations on being one of today's 10000. Google alt text, it's a short answer. The shortest answer is that it's the text that shows when you hover your mouse over an image.
It's a feature for all websites:
[...]alternative text (alt text) that is to be displayed in place of an element that cannot be rendered. The alt [text] is used for short descriptions[.]
The alt [text] is used to increase accessibility and user friendliness, including for blind internet users who rely on special software for web browsing.