Image caption – how to write a good one, and how it differs from alt text

Definition

An image caption is the visible text placed next to or below an image that explains it or puts it in context. In HTML it is often written with figure and figcaption. Unlike alt text, the caption is visible to every reader and is not an accessibility requirement.

What is an image caption?

An image caption is the visible text placed next to or below an image that explains what the image shows or puts it in context. Unlike file names or code hidden in the markup, the caption appears directly on the page for the reader to see.

In HTML, an image caption is usually written with the <figure> and <figcaption> elements, which tie the text to the image it belongs to:

<figure><img><figcaption>Image caption here</figcaption></figure>

Most editing tools, such as the rich text editor in many CMSs, have built-in support for image captions, so you rarely need to write the code by hand.

Image caption vs alt text – what is the difference?

Image captions and alt text are often confused, but they do different things. The caption is visible to everyone and adds context, a source or a point that is not obvious from the image itself. Alt text is invisible on the page and describes what the image shows for anyone who cannot see it – someone using a screen reader, for example, or when the image fails to load.

An important difference: an image caption is not an accessibility requirement. Alt text, on the other hand, is required under WCAG. The two do not compete; they complement each other. Ideally, use both and let them say different things rather than repeat each other.

How do you write a good image caption?

A good image caption adds something beyond the obvious. Do not just describe what the reader can already see – give context, a figure or a source, or explain why the image is relevant at this point.

• Do not repeat the heading or the alt text word for word.
• Keep it short and concrete – a sentence or two is usually enough.
• Credit the source or creator when the image is borrowed or quoted.
• Write for the reader first, not for the search engine.

Image captions, SEO and AEO

An image caption is visible text on the page that sits right next to the image, and readers who scan the page often stop at images and the text beside them. It gives search engines and AI extra context about what the image shows and how it relates to the content around it.

Do not count on image captions alone to lift your rankings, though – they are not a magic ranking factor. The value lies in making the content clearer for both readers and machines. Write them to help the reader understand the image, and you get the extra context as a bonus.