Alt text on social media: Instagram, LinkedIn, X and Facebook

Alt text is the written description of an image that a screen reader reads aloud in place of the picture. On social platforms it matters for a plain reason: the image carries part of your message, and a person who cannot see it receives only what is written down. If you add nothing, the platform may fill the gap with a machine-generated description, and Facebook's own help center says its automatic text may not always be complete. On X, the help center calls the description the only place that guarantees an image is described.

Where to add alt text on each platform

The table summarizes each platform's own help page as we read it on October 13, 2026: Instagram, LinkedIn, X and Facebook. Menus change, so treat the steps as a map. The Instagram and Facebook steps are the ones their pages give for a computer; both pages have tabs for the phone apps. LinkedIn's page shows that it was last updated 3 years ago.

Three of the four pages say who reads the text. Instagram and Facebook say it is read only when someone uses a screen reader, and LinkedIn says members who do not use one will not see it. X is different: its guide to writing image descriptions says everyone can access the description, and the ALT badge on a posted image opens it on screen. On X, write for every reader.

Two details are easy to miss. Only Instagram's and Facebook's pages describe changing alt text after you post, so on LinkedIn and X write it before you publish. And LinkedIn's page also covers images embedded in articles and, for advertisers, single image ads created in Campaign Manager.

What automatic alt text does, and why to replace it

Three of the four platforms describe an automatic fallback, each a little differently:

• Instagram says automatic alt text uses object recognition technology to provide a visual description of photos, and that you can replace it with a better description.
• Facebook says that when you do not include alt text, its Automatic Alt Text technology uses computer vision and artificial intelligence to create a description. A screen reader user hears either the text the uploader wrote or a list of objects, concepts or locations the image may contain, and the page says the automatic text may not always be complete (Facebook's page on automatic alt text).
• LinkedIn says it may add alt text to images that lack it. On desktop it alerts you when it does. On mobile it does not, so on a phone you may not know it happened.

A recognition system can name what it sees. It cannot know why you posted the picture. A photo of a cake might announce a product, share a recipe or celebrate a birthday, and the right description is different in each case. W3C's images tutorial says the text alternative has to be determined by the author, depending on the usage, context and content of the image. A post works the same way: you are the one who knows what the image is doing there. Treat the platform's text as a draft, keep it only if it says what the image means in your post, and replace it if it only lists objects. Our write-up on AI alt text accuracy shows that even a carefully configured vision model is good but not flawless at judging alt text, so read every draft.

How to write alt text for a social post

The rules are the same as anywhere on the web, with some adjustments for posts. W3C's tips for images suggest imagining that you are reading the page aloud over the phone to someone who needs to understand it. X's guide to writing great image descriptions adds advice that applies on any platform. Seven habits cover most posts:

1. Say what the image adds to the post. Describe what a sighted reader would take from it in the context of your post, not every visible detail.
2. Do not repeat your post text. X's guide says that if your post names a book's author and title, the description should cover the cover instead, and that if the post leaves those details out, the description should include them. Our guide to captions versus alt text explains how the two differ.
3. Put the most important detail first. W3C's tips say to aim for the most important information at the beginning.
4. Skip "photo of" and "image of". W3C says there is usually no need for words like image, icon or picture. X's guide agrees, and adds that it helps to say when something is a screenshot, a close-up or a black and white photo.
5. Write out the text in the image. X says to include it, to summarize it if it runs past 1,000 characters, and, for a legal document, to put the link to the source in the post rather than the description. W3C's decision tree says to put the image's text in the alt attribute when that text appears nowhere else.
6. Describe, do not editorialize. X's guide says to stick to what the image shows: say people are smiling rather than saying they look like they are having fun.
7. Keep it short. W3C says alt text should be the most concise description of the image's purpose. X's limit is 1,000 characters, and X says some screen readers once stopped reading at 200 to 250 characters, which is no longer the case, though you should still be succinct. See how long alt text should be.

The table uses an invented example: a cafe posts a photo of its chalkboard menu with the post text "Our fall menu is here."

For more worked cases, see our alt text examples, and for the full rules the complete guide to alt text.

Screenshots, charts, carousels and other hard cases

Screenshots and text graphics

Quote cards, announcements and screenshots of text are images of text. W3C's tutorial says to avoid text in images unless the image is a logo, and that where an image of text is used, the text alternative should contain the same words. In a post, that means writing the words into the description. Name a screenshot as a screenshot, as X's guide suggests. Our guides to images of text and alt text for screenshots go further.

Charts and infographics

A chart does not fit in one sentence. X's guide says to describe the trends and findings rather than explain the research behind them, and to link the source in your post. W3C's decision tree says that for a graph or other complex information, the same information should be included elsewhere on the page. In a post, that means the post text or the page you link to. Our guide to alt text for charts covers the longer pattern.

Posts with several images

X's help center says to select +ALT on each image in a multi-image post, and the ALT badge then appears on every image that has a description. The Instagram and Facebook pages likewise write their steps for a single photo, so give every image its own description.

People and pets

X's guide says to note people, pets and the relationships between them, with names when the names are relevant, and to stay objective about what is visible. Name a person only when you know who it is and the name matters to the post.

Video and decoration

The four help pages we read describe alt text for photos and images, not for video. Video with speech needs captions (see video captions and transcripts). On a web page a purely decorative image gets an empty alt attribute, per W3C's decision tree, but none of the four pages describes a way to do that in a post, so leave pure decoration out. See decorative images.

Does the law require alt text on social posts?

For some organizations it can, and the clearest case is state and local government in the United States. This is general information, not legal advice.

• The standard. Success criterion 1.1.1 Non-text Content (Level A) asks that non-text content presented to users have a text alternative that serves the equivalent purpose, with listed exceptions. Our plain-language explainer covers it.
• State and local governments. DOJ's fact sheet on the ADA Title II web rule says the rule requires WCAG 2.1 Level AA for web content and mobile apps. Compliance dates are April 26, 2027 for governments with populations of 50,000 or more, and April 26, 2028 for smaller governments and special district governments. The fact sheet's exception for social media covers only posts made before the date a government must comply, and it adds that a city that posted a picture in 2023 could give a blind person who asks for it a text description. So posts made on or after the compliance date fall outside that exception. See our Title II deadline guide and local government page.
• Businesses open to the public. DOJ's March 18, 2022 web guidance says businesses can choose how they make their online goods and services accessible, calls WCAG helpful guidance, and lists missing alt text on images among its examples of website accessibility barriers. See our ADA website compliance guide and the United States laws page, or the laws section for other countries.

Check it yourself

A routine for each image you post takes a minute or two:

1. Decide what the image adds to the post, and what the post already says.
2. Draft the description. The free alt text generator writes a first draft for each image you upload, in a descriptive, SEO or e-commerce style, and lets you add page context. It sees the image and whatever context you type, and it never guesses who people are, so add names yourself and read each draft against the post.
3. Edit the draft using the seven habits above, then paste it into the platform's field before you publish.
4. If the same image appears on your website, give it the same care there. The alt text checker reads a web page, downloads its images and judges whether each image's alt text is true of the picture, not only present. It takes a page address, so it cannot check text you are typing into a social app. Use it on the page of your own site where the image appears, such as a blog post or product page.

To find images with no alt attribute across your site's pages, Scan my site for free. It runs rule-based checks and says what a scan leaves to a person. The alt text and SEO guide covers alt text on your own pages and search, and the accessibility glossary defines the terms.