I often talk about adding alt text to images, but I never actually talk about what makes good alt text, for people who are unsure. So here's my perspective as a sighted person who sometimes uses a screen reader.
Tips for writing alt text for images and gifs:
- When sharing a screenshot of text, type out the text. If you're sharing a whole page but only highlighting a bit and the rest is irrelevent, only type the relevant part.
- Also give context of where it's from. "Screenshot of Reddit post. Text reads: ..."
- For images, give however much detail is relevant.
"Selfie!" Basic facial expression, hair, outfit, etc. might be fine.
"I love my nose!" Describe your nose.
Tweet about a tree with photo, but there are houses in the background? You prob don't need to describe each house.