Like describing a photo to a friend, how to write alt-text

15 May 2024

Web designers and bloggers have been able to use alternative text, often referred to as “alt-text”, to describe images and photos, for decades. Alt-text helps people with little or no vision comprehend a website image, so long as the description is reasonably accurate.

In recent years social media has caught up, and most channels, Instagram, Threads, Mastodon, and Bluesky among them, allow users to add alt-text to images they post.

The facility has left people wondering though about the best way to describe an image. Sadly, writing something like “a photo of my cat” as alt-text for a photo of a pet, doesn’t quite cut it.

A person with low vision knows your photo is of a cat, but is left wondering what sort of cat, what colour is the cat’s hair, and so on. So some degree of detail is useful.

Scott Vandehey, writing at Cloud Four, offers a straightforward suggestion for writing alt-text: imagine yourself describing something you’re looking at, to someone who you’re on the phone to:

I find people often get too wrapped up in what the “rules” are for alternative text. Sure, there are lots of things to be aware of, but almost all of them are covered under this simple guideline. If you were talking to a friend on the phone and wanted to describe a meme you saw, you might say “There was this dog wearing safety glasses, surrounded by chemistry equipment, saying ‘I have no idea what I’m doing.'”

The great thing about writing alt-text is the way you can write it once, say on a Notes file, but publish indefinitely, depending how many channels you end up posting the image to. It’s what I do now. Write a caption and alt-text first, then start posting across my socials.