Alt text 101 for Bluesky
Hi! You may be here because I or someone else sent you this link in response to a conversation about alt text on Bluesky. Welcome! This is a short article about alt text, its importance, and how to write it for social media!
What is alt text?
Alt text is text that describes an image. It's usually entered manually when a person posts an image. In some cases alt text may be autogenerated by software (usually not very well).
Why is alt text important?
Alt text is important to people with visual impairments and other types of disabilities. Some of these people use screen reader software, aka text-to-speech software, that reads text out loud to them. Since these people can't see the image, the presence of alt text helps them understand what the picture is and gives them context about it.
Other people with low vision may be able to read text but they may have difficulty making out details in images. In this case, they can read the alt text to get the context of the image.
Alt text is also useful and important to people with certain cognitive disabilities.
It's important that we include alt text for all* images on social media and elsewhere on the web. Alt text, and accessibility in general, are our ethical responsibilities to people with disabilities. We should not consider alt text to be optional.
(*There are some rare exceptions where certain images don't need alt text, but this does not apply to social media. An example of an image that doesn't need alt text is something that's purely decorative and that contains no information or context, like a divider graphic between sections of content on a website.)
How should alt text be written?
A great rule of thumb is: write alt text like you're describing the image to someone over the phone. What details are important for the other person to know about the image?
The main thing to consider is: what is the image supposed to convey to the viewer? What's the context?
Some guides for writing alt text will tell you to describe everything in the image. I think this is overkill in many cases. Things like the color of clothing are not relevant a lot of the time. I think if we insist that people write really detailed alt text, they'll be more likely to just skip it all together, which defeats the purpose. Simple and brief are fine, as long as you cover the most important things. If you want to write a lot of detail, just make sure to start with the most important things; that way a screen reader user can skip ahead if you start to get into less-relevant (/less-interesting) details.
If your image contains text, you should include all relevant text in the alt text.
How/where do I add alt text?
When you select a pic to post, it'll show you the pic with a little button that says "+ Alt"; you can tap/click that and add your alt text there.
For video, the link to add alt text will appear under the video when you've selected it; you might have to scroll down a bit.
Alt text and gifs
Most or all of the gifs that are available on Bluesky come with autogenerated alt text. In almost all cases, the autogenerated text is very bad! It's usually just a physical description of things, it's often wrong (which means it's probably generated by garbage AI), and it usually doesn't give any context of what the gif is about. Make sure to delete all that junk and write something that's actually useful!
I wrote some more about this topic: Bluesky, gifs, and autogenerated alt text.
Set alt text to be required in Bluesky
Bluesky has a setting that will remind you to include text when you're posting an image. Go to Settings / Accessibility, and check the box next to "Require alt text before posting." As of this writing (December 2024) you have to set this separately in both the mobile app and the desktop website.
Alt text and search
On top of our ethical responsibility to people with disabilities, alt text is also great for search. When you post an image with alt text, your post will appear in searches for the terms that you entered. You can easily search your own posts on Bluesky this way; just search "from:me term" — without quotes, and replace "term" with the word(s) you want to find.
That's the basics! There's really no need to overthink alt text! Just make sure to include it every time.
– Manning
Questions/comments? Feel free to contact me at manning@manningkrull.com. I update these articles pretty frequently — best practices evolve over time as the world of digital quickly changes, and I always welcome insights from others.