Alt text is a written description that makes an image understandable when someone cannot see it. For social media, describe the image’s useful information, include important words shown in the graphic, and leave out details that do not help the reader.
Think of a customer reading your post with a screen reader. If the picture disappeared, what would they need to know?
What is the difference between alt text and a caption?
A post caption introduces an idea, tells a story, or asks the audience to act. Alt text explains the image itself. The two should work together without forcing someone to hear the same paragraph twice.
For a pottery shop, the caption might announce a new collection. The alt text could explain the shape, color, and finish of the mug in the photo.
The W3C image decision tree provides the underlying principle: describe the meaning an image contributes in its context. Social platforms offer different controls, so use the description field available in your publishing tool.
Three useful alt text examples
Product photo
Weak: “Mug photo.”
Better: “Handmade blue ceramic mug with a curved handle and a speckled white rim, shown from the side.”
The second version helps a shopper understand the product. There is no need to describe the table unless the table matters.
Event announcement
Weak: “Our exciting event poster.”
Better: “Poster: Free product photography workshop, 12 November at 18:00, Studio North. Register through the link in the post.”
If the date and location already appear in the post text, focus the description on information that would otherwise be missing.
Simple chart
Weak: “Marketing performance chart.”
Better: “Bar chart comparing campaign sign-ups: email 120, paid social 85, and organic social 40. Email generated the most sign-ups.”
For a complex chart, include a fuller explanation or an accessible data table in the linked article. One short image description may not be enough.
A practical writing process
- Name the main subject or type of graphic.
- Describe the detail that matters to this post.
- Include essential words or numbers inside the image.
- Read the post and description together.
- Remove guesses, repetition, and unrelated detail.
Avoid guessing a person’s identity, feelings, or background from their appearance. Describe an observable action when it is relevant, such as “a person demonstrating how to fold the stand.”
Should alt text contain keywords?
Use the normal name of the subject when it helps explain the image. Do not add a list of search terms or turn the field into a second advertisement. “Red leather shoulder bag” is helpful when that is what the photo shows. Repeating “best bags, cheap bags, stylish bags” is not.
There is no universal ideal character count for every platform and image. Write as briefly as the meaning allows, and check the destination’s field limit.
Before you publish
Check that every meaningful image has a description, including individual images in a sequence. Review automatically generated text rather than assuming it is accurate.
Pair image descriptions with readable graphic text and video captions. These solve different access needs and belong in the same publishing workflow.