Alt text
What is alt text? It is a short written description of an image. Screen readers read it aloud, and browsers show it when the image fails to load. On social posts, good alt text says what the image shows and why it matters to the post, in a sentence or two.
Alt text
Example
Example: for a photo of a latte on a wooden table, write "Oat latte with leaf-shaped foam on a wooden cafe table."
Related documents
Related terms
- Instagram carousel: what a carousel post is
- Hashtag
- Social media audit
In Weekbird
Weekbird puts the week's posts on one calendar, so you can write image descriptions in the same sitting as the captions before anything goes out.
What is alt text
Alt text, short for alternative text, gives people who cannot see an image the same information the image gives everyone else. W3C's guidance asks you to describe what the image conveys in context. When an image only decorates, W3C says to leave the alt text empty so screen readers skip it.
Examples: before and after
Write for the post the image sits in. The same photo can need different alt text on a menu post and on a hiring post.
| Image | Weak | Better |
|---|---|---|
| Product photo | Coffee | Oat latte with leaf-shaped foam on a wooden cafe table. |
| Chart | Chart of sales | Bar chart: weekend orders doubled from 40 in June to 80 in September. |
| Decorative divider | Blue line | Empty alt text, so screen readers skip it. |
Where networks accept alt text
Limits come from each network's developer documentation. Where a network sets no limit, keep the description short anyway: a listener hears every word.
| Network | Alt text limit | Note |
|---|---|---|
| 1,000 characters | Images only, not Reels or Stories | |
| 4,086 characters | LinkedIn recommends under 120 | |
| 500 characters | Per Pin | |
| Bluesky | No length limit in the protocol | Per image, up to 4 images |
Checklist
- Say what the image shows that the caption does not.
- Put text that appears in the image into the alt text.
- Skip "image of" and "photo of".
- Leave decorative images empty where the network allows it.
Related terms
- Carousel post: each slide needs its own description.
- Hashtag: keep it in the caption, out of alt text.
- Social media audit: a good moment to check old posts for missing alt text.
Use it in your week
Write the descriptions in the same sitting as the captions, while you still have the images open. The alt text generator gives you a first draft to edit.