How to write alt text for social media

Alt text is a short written description of an image. Screen readers read it aloud to people who are blind or have low vision, and it shows in place of the image when it doesn't load. Instagram, X, Threads, Bluesky, LinkedIn, Facebook and Mastodon all have a place to add it, usually behind an Alt, Accessibility or Advanced settings option when you add the image.

What to put in it

The most important thing first. Many listeners move on after the first sentence, so lead with what the image is about.
What you see, plainly. People, objects, setting, colors and actions that matter to the post. Describe; don't interpret.
Every word of text in the image. Quote it exactly. This matters most for screenshots, quotes, flyers and memes, where the text is the point.
The medium when it isn't a photo. Say "Illustration of", "Screenshot of", "Chart showing" or "Meme:" so the listener knows what kind of image it is.
The viewpoint when it matters. A close-up, a selfie or an aerial view changes how an image feels.

What to leave out

"Image of" and "photo of". Screen readers already announce that it's an image.
Guesses about people. Don't guess someone's race, gender or age from how they look. Name people you know, and describe what's visible.
The caption. Alt text should add what the caption doesn't say, not repeat it.
Emoji and symbols. Screen readers read out each emoji's full name, and ™ or © marks become noise.
Hashtags and keywords. Alt text is for people, not for search.

How long should it be?

As long as it needs to be, and no longer. One or two sentences is enough for most photos. A chart, an infographic or a screenshot of a long post needs more, because every word and number in it is content. X allows up to 1,000 characters; if a platform's field is too short, put the rest in the caption or a reply.

Examples

Product photo: Weak: "Image of our new bottle."
Better: "A frosted glass water bottle with a bamboo lid on a white marble counter, next to a sprig of mint."
Screenshot of a post: Weak: "Screenshot of a tweet."
Better: "Screenshot of a post from @example: 'We're open late every Friday this summer.' It has 2,300 likes."
Meme: Better: "Meme: a cartoon dog sits in a room on fire, smiling, with the text 'This is fine.'"

Video

Most platforms don't have an alt text field for video. Add captions for anything that's said, and in the post or the first comment, describe what happens on screen that the sound doesn't tell you: who appears, what they do, and any text that shows up.

Get a head start

Describe writes a plain, objective first draft of alt text for an image, or a shot-by-shot description of a video, following the rules above. Read it over and add what only you know, like names and context. Caption adds captions to a video, and Transcribe writes a transcript.