OpenAccess

Accessible Social Media: Alt Text

Callum McMenamin — 28 June 2025

Alt text for social media images makes them accessible to blind people, among other benefits. This guide explains how to add alt text to your social media images, and why it’s important.

Alt text instructions

Facebook alt text instructions

1. Add an image to your post
2. Click ‘Edit’ in the top-left corner of the uploaded image
3. Click ‘Alternative text’
4. A text box to add custom alt text will appear
5. Select the radio button next to the text box to use the custom alt text, instead of the AI-generated alt text.
6. Type your alternative text description into the text box, and click Save.

Step 1

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Step 2

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Step 3

Bluesky alt text instructions

1. Add an image to your post
2. Click ‘ALT’ in the top-left corner of the uploaded image
3. Type your alt text description into the text box
4. Click ‘Save’

LinkedIn alt text instructions

1. Add an image to your post
2. Click ‘ALT’ below the uploaded image
3. Type your alt text description into the text box
4. Click ‘Add’

X alt text instructions

1. Add an image to your post
2. Click ‘Add description’ below the image
3. Type in your alt text description
4. Click ‘Save’

Instagram alt text instructions

1. Add an image to your post
2. Navigate past ‘Crop’ and ‘Edit’ options
3. Click ‘Accessibility’
4. Type your alt text description into the text box

What is alt text?

Alt text (or ‘alternative’ text) is intended to make visual images accessible for blind people. Blind people often rely on their computer to read content aloud using screen reader software.

Alt text may also benefit any person who may be using screen reader software to read social media posts. For example, people with dyslexia may use a screen reader or other text-to-speech software to read images of text aloud.

Generally, screen reader software can’t read out what images contain, or what they mean — screen readers typically only read out text and user interface controls (like buttons and links). So, each image needs a text-based replacement that the screen reader can read aloud. It’s up to content creators to write a text-based replacement of the image for screen readers to read aloud. This is what alt text is all about.

One way to think about alt text is: “what would I write down if I could not use an image here?” This helps you to think about how to write a replacement for the image. Alt text shouldn’t be a vague title — it should be a replacement that serves the same purpose as the image.

Some screen reader software can use AI to determine what an image is about, however it may not always be accurate — so it’s best for the content creator to write alt text descriptions manually.

Writing alt text can sometimes be more of an art than a science — it involves a subjective description of an image — two people might describe the same image in different ways.

How long should alt text be?

Alt text on social media posts should ideally be short, concise, and serve as an alternative to the image content. If your alt text ends up being paragraphs long, it might be best to consider whether the image is too complex; maybe the content could be conveyed in the post’s text instead.

Alt text is invisible

Alt text is invisible: something that’s really important to understand, is that you can’t actually see alt text descriptions. Alt text is basically a hidden piece of text that gets embedded into an image. When screen reader software encounters an image that has alt text, it will read the alt text description of that image aloud — even if you can’t see that text on the screen.

Social media alt text fails

Don’t put alt text as visible post text

It has unfortunately become increasingly common to see organisations attempt to put alt text on their social media posts, but they do it wrong.

Here’s an example:

In the above example, Whaikaha is making an effort to provide alt text descriptions for their social media images — great — but there’s one problem: they are putting the alt text descriptions in the actual visible post text.

Alt text is invisible — we shouldn’t be able to see the alt text descriptions. Social media platforms offer features to embed alt text into each image in a way that works for screen reader software. This means you don’t have to clutter your post’s text with alt text descriptions, and it actually provides a better, more usable experience for screen reader users.

Avoid images of text

Sometimes, images are used in social media posts which contain large amounts of text. Generally, images of text are not considered accessible. If you need to convey large amounts of text on social media, it’s best to put the text in the actual text of the post, rather than uploading an image of large blocks of text.

It’s acceptable if the image contains a small amount of text, such as a title of a blog post, a quote, or the name of a new product — but if the image contains more than ~15 words, it’s probably best to write the text in the post itself. If you do upload an image that contains a small amount of text, you should ensure its alt text description exactly matches the visible text in the image.

Here’s why actual text is better than images of text:

1. Screen reader software can read real text out loud to people who are blind or have low vision, without needing alt text.
2. Algorithms control what posts people see in their feeds — if text is inside an image, the algorithm can’t read it, so the post might not be shown to the right users, leading to poor engagement.
3. Users can make real text bigger, copy and paste it, or translate it.
4. If a user has dark mode enabled, real text will use the preferred colour scheme of the user, while images of text won’t change colour.
5. Real text stays sharp and easy to read, while text in images can look blurry or fuzzy.
6. Search (either via Google or in the social media platform) can find real text, but not text inside images.

In the above example, the Nelson Society of Modellers is responding to a fake news story I wrote claiming they are going to provide “light rail” to Nelson using miniature trains.

In this case, they uploaded a screenshot of the main text they are trying to convey, which is not an accessible way to convey that information. Instead, they should have put the main information in the post’s text itself, and they could have used the image area to provide some kind of engaging visual content to accompany the post.

Avoid automated or AI alt text

Some social media platforms like Facebook automatically add alt text to images if you don’t add your own. This can lead to inaccurate, incorrect, or potentially harmful information being read out by screen readers.

This is especially risky for high-stakes information, like in emergencies involving Civil Defence. Providing incorrect information via alt text could also lead to legal issues, such as false advertising claims.

Below is an example of a Facebook post made by Nelson City Council where they didn’t specify their own alt text, and Facebook’s AI-generated alt text was used instead.

The alt text of the image below, on Nelson City Council’s Facebook post was: “May be an image of text that says ‘GET Anoto READY ShakeOut TO Shght DROP s 代 COVER HOLD 27 OCTOBER 2022 9:30AM NATIONAL EARTHQUAKE DRILL AND TSUNAMI HĨKOI’”

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