Alt text or media description?
Alt text vs media descriptions: What’s the difference?
This year I took a course on Inclusive Communication (Bold Type by Ettie Bailey-King) and was surprised by how much time we spent on alt text - not just what it is, but actually writing it, submitting it for feedback and editing, over and over. It’s a whole thing.
I get asked about alt text a LOT, so I’m passing some of that knowledge on!
Alt text and media descriptions are two of the simplest ways to make your content more inclusive. They sound similar, but they’re not the same and they serve different purposes (and both will help your SEO!)
What is Alt Text?
Alt text is ‘hidden’ metadata that describes the essential content of an image. Screen readers read it aloud, and it appears on screen if an image doesn’t load.
Use alt text on all images, but pay particular attention when:
The image conveys information someone could otherwise miss (e.g. charts, quotes, diagrams)
The image is abstract or nuanced and was chosen for a reason (e.g. a yellow balloon to represent a feeling of optimism)
How long should it be?
Some screen readers may cut off alt text at around 100–120 characters. That’s one sentence, maybe two. (For my old school Twitter crew, that’s less than a Tweet!) If it needs more detail, that’s when you might want to use an image description as well.
Alt text example :
‘Two people sitting at a desk reviewing a brand moodboard with a laptop and colour swatches.’
Definitely not going to win any creative writing awards, but it's not supposed to - function over form!
Make it stand out
Whatever it is, the way you tell your story online can make all the difference.
What is a media description?
A media description (usually an image description and often shortened to ‘ID’) is visible text added directly into your content (not behind the scenes like alt text). It’s a sentence or short paragraph and it can benefit everyone, not just people using assistive tech.
Image descriptions are especially useful for:
People with low vision who may not be able to interpret visual detail
People who prefer written context over interpreting images
Anyone browsing without visuals (maybe because of image blockers or low bandwidth)
Social media, website platforms and content schedulers where alt text isn’t supported (this is usually the case with audio, video, pdfs and GIFs)
Media description example:
‘ID: Lauren leans over a desk scattered with colour swatches and half-formed logo sketches, deep in the flow of designing a new brand concept in a cosy studio with sunlight streaming in.’
Want more ideas like this?
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Best practices to start using now:
Use alt text to describe the meaning (what and why), not every pixel
For logos, write the business name instead of describing the logo
There’s no need to include ‘image of’ - screen readers already announce that
Use alt=" " for decorative images
Include any text shown in the image
Pair alt text with longer descriptions for complex visuals
Keep the tone neutral and factual
Don’t keyword-stuff for SEO
If you work in a team, create an internal guide for consistency
Remember to check if there's already alt text and/or media descriptions when you repost images - chances are you'll need to add them again
GIFs, video and pdfs need descriptions too!
By the way pdf documents themselves need alt text, but I'll write about that another day…
Can AI write alt text?
AI can generate quick first drafts, and it’s handy when you’re working at scale, but of course it comes with limits.
The main issue is that it doesn’t understand intent or nuance. It can tell you what’s there, not why it matters.
Further reading
If you'd like to explore how to make your content accessible in more detail, you might also find these articles helpful:
Why you should stop using "click here" in your links. Learn why descriptive link text makes emails and websites easier to navigate for screen reader users and improves the experience for everyone.
10 ways to make your emails more accessible. Discover simple improvements you can make to your emails, from writing effective alt text and descriptive links to choosing accessible colours, fonts and layouts that work better for everyone.
FAQS
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Alt text is hidden text added to an image that screen readers read aloud. An image description is visible text that provides additional context and can be read by anyone. Alt text is usually brief, while image descriptions can be longer and more detailed.
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Yes, but its primary purpose is accessibility. Well-written alt text helps search engines understand your images, can improve image search visibility and contributes to a better user experience. Avoid stuffing alt text with keywords, as it should accurately describe the image rather than target search rankings.
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Alt text should be concise while still communicating the purpose of the image. In most cases, one sentence is enough. If an image requires a much longer explanation, use a visible image description alongside the alt text.
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Decorative images should use empty alt text (alt="") so screen readers skip them. This prevents unnecessary interruptions and improves the experience for people using assistive technology.
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AI can generate a useful first draft, but it often misses context, emotion and intent. It's best to review and edit AI-generated alt text so it accurately reflects why the image is included, not just what appears in it.
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Yes. Rather than describing the appearance of the logo, use the business or organisation's name. For example, use "Lauren Sherrard Design" instead of describing the colours, shapes or typography.
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Yes. While many platforms now support alt text, image descriptions remain useful because they're visible to everyone and can provide additional context for complex images, graphics, videos, GIFs or PDFs.
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Yes! Some other tips:
Videos need captions and audio descriptionsPDFs need tagged accessibility and alt text for images
GIFs should include a description if they convey meaning
Charts and infographics often need both alt text and a longer image description