Alt text on Bluesky: what to do with a 2,000-character field

Most alt text fields are a cramped little box. TikTok stops you at 300 characters. Pinterest at 500. X and LinkedIn both cut off at 1,000. Bluesky gives you 2,000 — more room than any other major social platform, and enough that how much to write becomes an actual decision instead of a limit you bump into.

Here's where the field lives, and what that extra room is genuinely for.

Where the field is

Same two steps on desktop and mobile. Add your image to the composer, then click the +ALT button in the image's upper left corner. Write the description on the next screen and click Save. The button then shows a checkmark instead of a plus, which makes a last glance before posting easy: every image should be wearing a check.

There's also a setting worth turning on. Under Settings → Accessibility, toggle the alt text reminder. With it on, Bluesky won't let you publish a post whose images have no description. X has a similar nudge you can wave away; Bluesky's you can't. If several people post from one brand account, that toggle is the closest thing to an enforceable policy you can set with a switch.

2,000 characters is a ceiling, not a target

Room to write is not an instruction to fill it. A photo of a person at a podium still needs one clear sentence, and padding it out doesn't help anyone — a screen reader user is listening to every word in real time, and long alt text on a simple image is just a longer wait for the same information.

The ceiling matters for the images that honestly can't be handled in a line: infographics, data charts, event flyers, screenshots of text. On platforms with a 1,000-character cap you often have to choose which numbers survive. On Bluesky you don't.

The strong version is 155 characters — well past the usual 125-character guidance, and entirely appropriate here, because every one of those characters carries information someone would otherwise lose. Length should follow the image, not the field.

The rule that should change your workflow

On Instagram and LinkedIn, alt text is fixable after the fact — you can go back into a published post and add what you forgot. Bluesky has no retroactive edit for image descriptions. If the alt text is wrong, or missing, the only fix is deleting the post and publishing it again, which costs you every like, repost, and reply it had collected.

So on Bluesky, alt text can't be the cleanup task you push to Friday afternoon. It has to happen in the thirty seconds before you hit post, which is exactly the moment teams are most likely to skip it. Turning the reminder on removes the option to forget.

Your description is public, so write it like it

Bluesky shows an ALT badge in the lower right corner of any image posted with a description, and anyone can click it to read what you wrote. That's a useful discipline: alt text here isn't buried metadata that only a screen reader will ever surface. Sighted followers can read it too, and some will. Write the sentence you'd be happy to have quoted.

None of this is hard. It's just one more thing to do at the moment you have the least patience for one more thing — which is why the reminder toggle and a fast way to draft the description matter more than any rule about length.