A picture says a thousand words, and sometimes it can be tempting to describe something in as many words when writing image descriptions for visual content. While image descriptions should refrain from over-describing images or including irrelevant visual details, there are cases where image descriptions need to go beyond the character limit in a social media post to ensure that key elements of the image are communicated to audiences that are visually impaired (inclusive of blind, low vision, neurological visual impairment, and other forms of vision loss). Here is a list of options for writing extended image descriptions on social media, and best practices for doing so.
What is alt text? What is an image description?
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). 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.
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 somewhere the user can easily find it.
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. BlueSky is one social media platform that allows 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. I usually recommend people keep basic descriptions at around 280 characters, or the length of a short text post.
Here are the policies for alt text on popular social media platforms, copied from my post on How To Add Alt Text on Social Media.
- X supports alt text up to 1,000 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.
- 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 500 characters, and alt text can be added to static/image or video pins after they are posted.
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.
Related links
- How To Write Alt Text and Image Descriptions for the Visually Impaired
- How To Create Image Descriptions For Red Carpet Looks
- How To Write Alt Text and Image Descriptions For Jewelry
- How To Add Alt Text On Social Media
Example use cases for extended descriptions
Wondering why someone would need to write an extended image description that goes beyond typical length or word count recommendations? Here are some example use cases:
- Screenshot of text, such as an article, note, or story
- Scenes from comics or graphic novels that require detailed descriptions or that contain lots of text
- Images where every single element is important to understand the meaning of an image, and descriptions are longer than the allotted character limit
- Images that are stitched together and posted as one image- users can set alt text for individual photos in a gallery view as an alternative
- Images that contain lots of details or important symbols
- Intricate artwork or costumes
- Scenes from comics or graphic novels that require detailed descriptions or that contain lots of text
- Educational images that are meant to introduce someone to a topic or item they have never seen before, and to build a visual model for what something looks like
- Video descriptions, which can be presented as transcripts and provide information about audio and visual content presented in a video.
Related links
- How To Write Image Descriptions For Cosplay
- How To Write Video Descriptions For Animal Videos
- How To Write Video Descriptions For TikTok
- How To Describe Dance Choreography Videos For Visually Impaired
- How To Write Alt Text For Memes
- How To Write Alt Text For Gifs
Should I post both alt text and an image description?
When posting an extended image description to accompany a photo or other content, I recommend including alt text for the image, as in a basic description of what the image looks like. Do not post links in the alt text box, as these are not clickable.
In the post caption, include a link to an extended description at the beginning or end of the post caption, writing something like [ID: Hyperlink] or [ID: See comments] so that the user can click the link or copy/paste it to access the extended description. The term “Image Description” may also be used instead of ID.
Related links
- My Ideas For Improving Alt Text Features On Social Media
- How To Write Alt Text For Color Palettes
- How To Write Alt Text For Casual Outfits
- How To Improve Your Blog Theme For Visually Impaired Users
If sharing a screenshot, link the original source
For content such as news articles, blog posts, or other online information, an alternative to sharing an extended image description would be to instead share the original source link, either as a shortened link or the full URL in the caption so that the user can view the information on the original website. To make text easier to read and apply a consistent font size and style, simplified reading displays like Reader View, Immersive Reader, and other extensions can be used to display text in large print.
For data visualizations and charts, sharing a link to the CSV file with the original data is good practice so that users can explore it on their own. However, I recommend including a basic description of what the chart looks like as an image description, in addition to the CSV link.
Related links
- Simplified Reading Displays and Low Vision
- Google Reader Mode and Low Vision
- Adapting Accessible Charts: Math Problems and Low Vision
- How To Create Accessible Pie Charts For Low Vision
Write everything out in a thread or comment
Another option for “overcoming” the character limit is to post the image description in a pinned comment, so that it is easier to find and is not affected by other information in the original caption such as hashtags. This can also be used to describe individual panels or images in a gallery.
For text-based platforms like X, BlueSky, and Mastodon, a thread can be created for an extended image description of a specific type of content; I recommend numbering each post in the thread and posting a link to the thread as a reply or quote to the original image.
Link to a plain text copy of an image description
Plain text files with Markdown and plain text files without Markdown are generally accessible to screen reader users and can be enlarged to display large print, so this is another option for extended image descriptions. There are several popular websites that allow users to post plain text that cannot be edited or deleted later, though one of the most widely used ones that I have seen is Pastebin. Most users will write out the extended description in Pastebin and then share the link in a post caption or comment.
Related links
- Pastebin website
- Tips For Using VDWrite In The Classroom With Low Vision
- File Formats For Low Vision and Print Disabilities
- A to Z of Assistive Technology for Reading Digital Text
Create a dedicated website for hosting extended image descriptions
For artists or people who regularly post their own image content, another option would be to create a simple blog or website that posts extended image descriptions for individual posts. XKCD is one example of a digital comic that takes this approach for sharing alt text online, and I frequently recommend this for comic artists specifically because of the visual nature of the medium.
Related links
More tips for writing extended image descriptions on social media
- Need a refresher on how to write image descriptions? Read How To Write Alt Text and Image Descriptions for the Visually Impaired
- Instead of copying things like ASCII memes or emoji memes as extended descriptions (a format that is inherently inaccessible to screen reader users), I recommend describing what the emoji or symbols form, such as a word, phrase, or symbol. Learn more in How To Make ASCII/Emoji Memes Accessible For Visual Impairment
- Want more alt text content? Browse Alt Text Archives | Veronica With Four Eyes (veroniiiica.com)
Published May 28, 2020. Updated November 2024