A caption and an alternative text description can refer to the same image while doing different editorial work. The caption usually gives visible context for the reader: where the scene is, why it matters to the article, who is involved when their identity is known, and who supplied the image. Alt text conveys the image’s relevant information or function for someone who cannot see it. Writing one sentence and copying it into both fields often leaves one of those jobs unfinished.
Imagine an article about river tourism illustrated with a photograph of a sightseeing boat passing colorful buildings. A useful alt description might be “A sightseeing boat passes riverside buildings beneath a pedestrian bridge.” A caption could add the verified city, river and circumstances, then credit the host or photographer. The location may belong in alt text too if it is essential to the image’s purpose in that article. These fields do not have a rigid rule against sharing information; the question is what the reader needs in each place.
The mistake is treating alt text as a second storage field for every fact you know. Booking advice, a long history of the waterfront, an uncertain identification and a string of search keywords can bury the visual information. Put explanation in the surrounding article, and use a caption for concise context that helps readers understand the illustration. W3C’s image guidance makes purpose and context central to the text alternative. A short description of appearance is useful only when it communicates the information the image contributes.
The reverse mistake is writing a caption that merely repeats the visible objects. “Boat on river” supplies little help when those objects are obvious to a sighted reader and the article already discusses them. A better caption connects the image to the story. It might identify the departure area, explain which part of the route is shown, or distinguish a scheduled sightseeing service from a private vessel, provided those facts have been checked. Avoid turning guesses into confident labels.
Credit is another separate responsibility. An image-hosting credit should identify and link to the relevant host, while authorship should be attributed accurately when known. A hosting site is not automatically the photographer, copyright owner or rights licensor. Keep those distinctions clear. The alt field is usually a poor place for routine credit because it interrupts the description with information better carried in the visible caption or nearby credit line. Legal attribution requirements still need to be satisfied in the appropriate visible location.
Consider a second example: a poster displayed above a desk. If the article is about arranging the wall, the alt text should describe the placement and relevant visual relationship. If the article is about the poster’s design, the artwork’s shapes and colors deserve more attention. A caption can identify the work and explain whether the scene is a proposed arrangement. The same photograph may need a different text alternative in a different article because its editorial function has changed.
Linked images need an additional check. If an image acts as the only link to a larger version, a product or another page, its accessible description must make the link’s purpose understandable. Decorative images can use an empty alt attribute when they add no information and have no independent function. That decision depends on context; an image should not be declared decorative merely because describing it would take effort. Charts and complex diagrams may need fuller explanations elsewhere in the page.
A practical editing pass is to read the article without looking at the images, including the text alternatives in their actual context. Then review the visible page with its captions. Does either reading leave out information the other depends on? Does the screen-reader version repeat the same paragraph needlessly? Are identities and locations stated with more certainty than the evidence supports? These checks catch problems that a word-count target cannot.
MediaGallery’s accessible gallery guide covers the wider page, including navigation. At the individual-image level, assign each field a clear task and edit it accordingly. Alt text should carry the image’s useful contribution; the caption should connect that image to the story. When those two decisions are made together, both forms of reading become more coherent.