Give each piece of text a different job
A caption often tells readers why a photograph is there. It might name a person, identify a location, explain when something happened or connect the image to the surrounding story. Alt text describes the visual information a reader needs when the photograph itself is not available to them. The two can overlap, but they do not have to repeat each other word for word.
Imagine a project page with a photograph of a designer arranging paper samples on a table. The caption says, “Testing materials for the new packaging identity.” Repeating that sentence as alt text leaves out what the photograph shows. A more useful alternative might be, “A designer compares cream and blue paper samples beside a folded packaging prototype.” The caption supplies the project context; the alt text supplies the visible detail.
Decide what the photograph contributes
Before writing, look at the photograph alongside its heading, body copy and caption. Ask what a reader would miss if the image disappeared. Is it showing a process, an object’s appearance, a spatial relationship or a contrast between two outcomes? Start with that contribution rather than listing everything in the frame.
Context changes the answer. On a portfolio page about lighting, “A ceramic bowl casts a long shadow across a pale backdrop” may be more useful than identifying the bowl alone. On a page about the bowl’s surface finish, the matte glaze and uneven rim may matter more than the shadow. Alt text is not a complete inventory; it is a considered description of the details that serve this particular page.
Describe what is visible, not what you assume
Useful alt text is specific without guessing. You can describe a person holding a camera at eye level, but you may not know whether they are preparing a portrait or reviewing a shot. You can describe a crowded workshop table, but “a successful brainstorming session” is an interpretation unless the surrounding text establishes it. When a name, place or purpose is confirmed in the caption, there is no need to infer it from appearance.
Choose concrete nouns and actions: “three participants pin sketches to a wall” usually conveys more than “people collaborating.” Include colour, composition or expression when those details help explain the photograph’s role. Leave out incidental objects unless they matter. You rarely need to begin with “Photo of”; the image format is generally apparent from its placement, while the description can get straight to the subject.
Work with the caption, not around it
Try reading the caption and alt text together. If they sound like two versions of the same sentence, give each a clearer task. For a photograph captioned “Final identity applied to the exhibition entrance,” alt text could say, “Large red lettering spans a white wall above the entrance doors.” The caption explains the application; the alt text conveys its appearance and scale.
Sometimes a short repetition is unavoidable. If the essential visual fact is that a specific object appears, naming it in both places can be clearer than using a vague substitute. The aim is not to ban shared words. It is to avoid making someone hear the same information twice while leaving out the visual detail that made the photograph worth including.
Use a quick editing exercise
For your next set of photographs, write a one-sentence answer to each of these questions: What does the caption tell me? What can I see that the caption does not tell me? Which of those visible details matters to this page? Turn the final answer into a concise description, then read it beside the caption. Remove repeated phrases, unsupported interpretations and details that do not help.
Finally, consider whether the photograph adds information at all. If it is purely decorative and contributes nothing beyond nearby text, an empty alt attribute may be appropriate on a website. If it shows a design decision, a step in a process or a result readers are meant to examine, describe that contribution. This small review helps captions carry the story while alt text makes the photograph’s useful visual information available.
