Instagram Alt Text Character Limit 2026

The Instagram alt text character limit is 100 characters, well under the 2,200 character caption limit and even under the 150 character bio limit. Alt text describes an image for screen readers used by blind and low vision users, and Instagram's screen reader integrations also tend to cut off anything past roughly 125 characters, so staying inside the 100 character guideline keeps your description fully intact for the people relying on it.

Why alt text length matters more than caption length

A caption can ramble; alt text cannot. Someone using a screen reader hears your alt text read aloud before anything else about the post, so every character needs to describe what is actually in the image rather than repeating your caption or adding a call to action. Vague or padded alt text ("photo" or "image of a person") fails the one job it has: telling a screen reader user what they cannot see.

How to write alt text in 100 characters

Focus on concrete, visual detail in the order it would matter to someone hearing it read aloud:

• Lead with the subject: "Woman in a yellow raincoat" not "A photo of a person outside"
• Add the action or setting if there is room: "Woman in a yellow raincoat walking a dog on a rainy street"
• Skip words that add nothing visual: "beautiful," "amazing," "must-see"

That example runs 61 characters, leaving room to spare. Most useful alt text descriptions land between 60 and 100 characters once you cut filler words.

Where to add alt text on Instagram

Instagram lets you add custom alt text from the "Advanced Settings" screen when creating a post, before you tap share. If you skip it, Instagram generates automatic alt text using image recognition, which is functional but often generic ("may contain: person, outdoor, sky") compared to a description you write yourself.

Alt text for carousels

Each image in an Instagram carousel gets its own separate alt text field, not one shared description for the whole post. Write a distinct 100 character description for every slide rather than repeating the same line across all of them, since a screen reader user hears each slide's alt text individually as they move through the carousel, and identical descriptions across five different images tell them nothing useful about what changed from one slide to the next.

A quick habit that pays off

Writing alt text takes an extra ten seconds per post and makes your content usable to a meaningfully larger audience, plus Instagram has indicated alt text and image descriptions factor into how content gets indexed. Check your caption length separately with the Instagram caption counter so alt text and caption are not competing for the same mental space while you write. Create a free account and schedule your Instagram content through the Instagram scheduler alongside the other nine platforms Posted Once supports.