Your carousel needs 10 alt texts, not one

A 10-slide Instagram carousel has 10 alt text fields. Almost every carousel published this year has zero. Not because anyone decided against it, but because the fields are buried 3 taps deep and nobody is watching.

Who this actually affects

Start with the number, because it changes how seriously people take the rest. Somewhere around one in 20 people has a vision impairment significant enough to affect how they use a phone. On an account with 10,000 followers that is several hundred people for whom your post is a blank.

Screen readers announce alt text where it exists. Where it does not, Instagram and Facebook substitute an automatic guess, which produces things like “may be an image of one person and text”. Technically a description. Useless as one.

And it is not only permanent impairment. It is a cracked screen, bright sun, a slow connection that never loads the image, and anyone who has turned images off to save data.

What each platform gives you

Instagram. Alt text per image, including every slide of a carousel up to 10. This is the one most often missed, because it is per slide rather than per post.

Threads. Per image, on up to 10 files.

Bluesky. Per image and, unusually, on video too. Still rare across the industry.

Pinterest. Alt text up to 500 characters, and it does double duty: Pinterest is a search engine wearing a feed, so the description does ranking work as well as accessibility work.

LinkedIn and Mastodon. Per image.

X. Per image, though it is easy to skip in most tools.

Video captions are a separate problem with a bigger audience. Most video on social is watched with sound off, which means captions are not an accessibility extra; they are the only way most people consume it at all.

How to write one that works

Alt text is not a caption and it is not a place for keywords.

Describe what matters, not everything. “A barista pouring a flat white, seen from above” beats a full inventory of the counter.

Read the text in the image. If a slide says “3 ways to cut your reply time”, the alt text says that. An image of text with no alt text is completely lost.

Keep it to a sentence. Around 125 characters is the practical limit before a screen reader gets tedious.

Skip “image of”. The screen reader already said it is an image.

Decorative means empty. A background texture with nothing to communicate should have empty alt text rather than a description of the texture.

The carousel problem, specifically

A carousel is usually a sequence: a hook, then steps, then a conclusion. Each slide is a separate image with separate alt text, and treating them as 10 independent descriptions loses the thread.

Write them as a sequence too. Slide one sets up what the carousel is. Slides two to nine each carry their own point. The last one carries the call to action, because a listener who reaches the end should know what to do next, the same as everyone else.

It takes about 4 minutes for 10 slides. That is the entire cost.

Where AI genuinely helps

This is the one part of social media work where generated text is unambiguously better than the alternative, because the alternative is nothing.

A model reads the image and produces a usable description in a second. It will miss context it cannot see, so skim it and fix the one in 10 that is wrong. But the comparison is not “AI alt text versus excellent hand-written alt text”. It is “AI alt text versus a blank field”, and the blank field is what almost everyone ships.

If your tool can generate it per slide, the 4 minutes becomes 20 seconds and the excuse disappears.

The reach argument, for the sceptics

If accessibility on its own does not move the decision, there is a second reason.

Alt text is text the platform can read. On Pinterest it directly affects whether a pin surfaces for a search. Across the others, it is one more signal about what the post is, in a system that mostly guesses from engagement.

It will not transform your reach. It costs 4 minutes and helps several hundred people per 10,000 followers actually see what you published, which is a better return than most things on the calendar.

EngageDigital exposes alt text per carousel slide rather than one field per post, and can draft it from the image itself. See how publishing works or join the early-access list.