How To Add Alt Text On Social Media

When people ask me if I have any tips for improving accessibility of social media posts, I like to ask them if they know how to add alt text on social media platforms. While a lot of people know how to add alt text on one or two platforms, the truth is that alt text has to be added manually across all social media platforms so that blind and visually impaired users can understand what is in an image. It only takes less than a minute to add alt text to social media posts, so it’s an easy way to ensure that audiences who use assistive technology are not excluded. Here are my tips for how to add alt text on social media for common platforms.

What is alt text? What is an image description?

Alternative text (alt text) and image descriptions are text-based descriptions of visual details in an image written primarily for people who are visually impaired (inclusive of blind, low vision, and neurological visual impairment). If an image fails to load on a website, alt text will be displayed in its place, and alt text is also used for search engine optimization and image search tools.

Image descriptions are similar to alt text descriptions that are used by screen readers to recognize images, though there are a few key differences between alt text and image descriptions:

LOCATION

Alt text is typically attached to an image metadata or added in the “alt text” box on social media. Image descriptions may be in the image caption, in a text post, or shared in a text link for extended descriptions.

VISIBILITY

Alt text is usually only visible to screen readers, which read the alt text out loud or display it on a braille display. Image descriptions are “exposed” and can be read by anyone. Saving an image does not save its alt text.

BlueSky, X, and Mastodon are examples of social media platforms that allow users to read alt text whether they have a screen reader or not by selecting the ALT button on an image or gif that has alt text included.

LENGTH OF TEXT

A picture is worth a thousand words, but there may only be room for a thousand characters! Alt text is typically limited to 100-250 characters, though most best practice guides recommend keeping alt text to around 125 characters. Image descriptions can be the same length or even longer, since they are included in the photo caption, in a text post, or text link.

For social media platforms that have larger character limits for alt text, many users will write longer image descriptions in the alt text field, and reprint the same descriptions in the caption of the post. However, this is not completely necessary for platforms that offer exposed alt text that can be viewed without a screen reader.

LEVEL OF DETAIL

Image descriptions tend to go more in-depth about visual details than alt text due to the larger character limit. For example, alt text might tell a user there is a puddle on the floor, but an image description might go into further detail and say there is a puddle of orange juice on a white tiled kitchen floor.

It’s worth noting that some people will use the same text for both alt text and image descriptions, which is an accepted practice. However, I prefer to include more detailed descriptions as exposed image descriptions so everyone can read them whether they have a screen reader enabled or not.

SHOULD I USE BOTH ALT TEXT AND IMAGE DESCRIPTIONS?

I recommend using both alt text and image descriptions when possible, since image descriptions can also be read in large print or by people who aren’t using screen readers. Some people use the same text for both, while others prefer to write more detail in exposed image descriptions and treat them like image captions. Another strategy to share lengthy image descriptions on social media is to write a basic description of the image as alt text and then link an extended image description to read on another page.

When sharing exposed descriptions, I recommend using the label “ID:” or “Image Description:” in front of the text so that it is easier to locate. Some creators choose to enclose the description in parenthesis or brackets, which is also helpful for separating the description from the rest of the caption. Using the label “Alt text:” in a caption is also acceptable and conveys the same message, but the term image description is more appropriate— some users will use the terms alt text and image description interchangeably to refer to exposed image descriptions that anyone can read.

Related links

• Alt Text category on Veronica With Four Eyes
• How To Write Alt Text and Image Descriptions for the Visually Impaired
• How To Write Alt Text For Digital Comics
• How To Write Alt Text For Memes
• How To Access Images Without Alt Text
• Options For Writing Extended Image Descriptions On Social Media

Twitter (X)

Twitter (X) supports alt text up to 1,000 characters, though alt text cannot be added or edited once an image or gif is posted.

To add alt text to Twitter/X posts:

1. Create a new tweet and attach an image or gif
2. Select “add description” underneath the image
3. Type alt text of your choice
4. Select “done” when finished

Alt text can be added to tweets that contain multiple images, though each image will need its own alt text. Alt text can be read without a screen reader by selecting the ALT icon on an image with alt text.

Related links

• Accessibility And Low Vision Twitter Lists To Follow
• Twitter Accessibility Features For Low Vision
• How To Write Alt Text For Gifs
• Texting and Low Vision

BlueSky

BlueSky supports alt text up to 2,000 characters, though alt text cannot be added or edited once an image is posted.

To add alt text to BlueSky posts:

1. Create a new post and attach an image or gif
2. Select “add description” underneath the image.
3. Type alt text of your choice. Some gifs will load with automatically generated alt text, which can be edited.
4. Select “done” when finished

Alt text can be added to posts that contain multiple images, though each image will need its own alt text. Alt text can be read without a screen reader by selecting the ALT icon on an image with alt text.

Mastodon

Mastodon supports alt text up to 1,500 characters, though alt text cannot be added or edited once an image or gif is posted. Some Mastodon instances may offer a higher character limit.

To add alt text to Mastodon posts:

1. Create a new post and attach an image or gif
2. Select “add description” underneath the image
3. Type alt text of your choice
4. Select “done” when finished

Alt text can be added to posts that contain multiple images, though each image will need its own alt text. Alt text can be read without a screen reader by selecting the ALT icon on an image with alt text.

Instagram

Instagram supports alt text up to 100 characters, and alt text can be added or edited once a picture is posted.

TO ADD ALT TEXT TO NEW INSTAGRAM POSTS:

1. Create a new post
2. Select “compose alt text” underneath advanced settings of the post
3. Type alt text of your choice
4. Select “done” or the check mark when finished

TO ADD ALT TEXT TO EXISTING INSTAGRAM POSTS:

1. Select the three vertical dots at the top of the post
2. Select “edit”
3. Tap the “alt text” option that is directly on top of the photo, next to the “tag people” option.
4. Add your own alt text and save it to the photo

Related links

• How To Make Your Instagram Feed Accessible For Visual Impairment
• How To Make Instagram Stories Accessible For Low Vision Users

Threads

Threads supports alt text up to 1,000 characters, though alt text cannot be added or edited once an image is posted.

To add alt text to Threads posts:

1. Create a new post and attach an image
2. Select “Edit Photo”, then select “Alt Text”
3. Automatically generated alt text will display on the left side of the image. This can be edited by selecting “override generated alt text”
4. After overriding generated alt text, type alt text of your choice
5. Select “save” when finished

Alt text can be added to posts that contain multiple images, though each image will need its own alt text.

Facebook

Facebook supports alt text up to 100 characters, and alt text can be added or edited once a picture is posted.

To add alt text to new Facebook posts:

1. Create a new post and attach an image
2. Select “Edit Photo”, then select “Alt Text”
3. Automatically generated alt text will display on the left side of the image. This can be edited by selecting “override generated alt text”
4. After overriding generated alt text, type alt text of your choice
5. Select “save” when finished

To add alt text to existing Facebook posts:

1. Select the photo to open it.
2. Select “Options” in the bottom right and then select “Change Alt Text”
3. If needed, select “Override generated alt text” or change the alt text in the text box
4. Select “save” when finished

Related links

• Emoji and Low Vision
• How To Make ASCII/Emoji Memes Accessible For Visual Impairment

Tumblr

Tumblr supports alt text up to 4,096 characters, and alt text can be added or edited once a picture or gif is posted.

To add alt text to new Tumblr posts:

1. Create a new post and attach an image
2. Select the three vertical dots in the lower right-hand corner of the post (web users may need to hover their mouse over the image)
3. Select “Add Alt Text” (mobile) or “Update Image Description” (web)
4. Add your own alt text and save it to the photo

To add alt text to existing Tumblr posts:

1. Select the three dots in the top-right corner of a post and select Edit
2. Select the three vertical dots in the lower right-hand corner of the post (web users may need to hover their mouse over the image)
3. Select “Add Alt Text” (mobile) or “Update Image Description” (web)
4. Add your own alt text and save it to the photo

Related links

• How To Make Tumblr Themes Accessible For Low Vision
• How To Write Image Descriptions For Cosplay
• How To Write Video Descriptions For Animal Videos

Pinterest

Pinterest supports alt text up to 800 characters, and alt text can be added or edited after a static (image) or video pin is posted.

To add alt text to new Pinterest posts:

1. Create a new pin and attach an image or video
2. Add a title, description, and destination link- I recommend copy and pasting the alt text into the pin description
3. Select the publishing time for the new pin- publish it immediately or save/schedule it for later
4. The Alt Text field will become visible once the publishing time is set, and users can enter their desired alt text
5. Select a board for the pin and it will automatically save

To add or edit alt text on existing Pinterest posts:

1. Navigate to the pin that you want to add alt text to
2. Select Edit Pin
3. Add text to the Alt Text field
4. Tap Done to save changes

LinkedIn

LinkedIn supports alt text up to 120 characters, and alt text cannot be added or edited once a picture is posted. Alt text also cannot be added or edited on mobile apps.

To add alt text to new LinkedIn posts:

1. Create a new post and attach an image
2. Select “add alt text” which can be found on the lower left side
3. Add your own alt text and save it to the photo

Summary of how to add alt text on social media

• Alt text is a text-based description of images that is used by screen readers to describe what is in an image for people who cannot see it
• An image description gives more details than alt text and allows someone to learn more about what is in an image that goes beyond alt text, and is often included separately
• Twitter (X) supports alt text up to 1,000 characters, though alt text cannot be added or edited after an image or gif is posted.
• BlueSky supports alt text up to 2,000 characters, though alt text cannot be added or edited after an image is posted.
• Mastodon supports alt text up to 1,500 characters, though alt text cannot be added or edited after an image or gif is posted.
• Instagram supports alt text up to 100 characters, and alt text can be added or edited after a picture is posted.
• Threads supports alt text up to 1,000 characters, though alt text cannot be added or edited after an image is posted.
• Facebook supports alt text up to 100 characters, and alt text can be added or edited after a picture is posted.
• Tumblr supports alt text up to 4,096 characters, and alt text can be added or edited after a picture or gif is posted.
• Pinterest supports alt text up to 800 characters, and alt text can be added to static/image or video pins after they are posted.
• LinkedIn supports alt text up to 120 characters, and alt text cannot be added or edited after a picture is posted

Published October 8, 2019. Updated November 2024