How to write image descriptions that help people understand the page

Start with the image’s job

Before writing alternative text, ask why the image is on the page. Does it identify a person, show a product, demonstrate a process, provide evidence, communicate a result or act as a link? The answer determines the description. A useful description communicates the image’s role in the page, not a catalogue of everything a camera captured.

For example, a service page may show a completed bathroom renovation. If the image supports the claim that the business handles accessible layouts, the description might mention the level-entry shower and grab rails. If it is only a mood photograph beside the same explanation, the useful content may already be in the text and the image can be decorative.

Read the paragraph and heading around the image first. The description should add missing information, not repeat the caption word for word. Context changes meaning: the same photograph may need a different description in a case study, product page or team biography.

Decide when an image is decorative

Decorative images add atmosphere, spacing or visual interest but no information needed to understand or use the page. Examples include a background texture, a divider, a repeated brand pattern or a stock photograph that adds no new meaning. For these images, an empty alternative text value is often appropriate so assistive technology can skip them.

Do not call an image decorative simply because writing text feels difficult. If removing the image would make a claim, instruction, product choice or link less understandable, it contributes meaning. Describe that contribution or provide the information elsewhere in accessible text.

Repeated icons need careful treatment. If an icon sits next to a visible label, it may be decorative. If it is the only indication of search, download, warning or status, it needs an accessible name. A visual symbol is not automatically understood by everyone.

Describe informative images briefly

An informative photograph usually needs a short, specific description. Mention the subject, action and relevant context. “A person” is too vague; “A mechanic checks the electrical panel in a renovated kitchen” gives a useful idea. You do not need to mention every colour, object or background detail unless it matters.

Avoid starting with “image of” or “photo of” when the technology already announces that an image is present. Avoid opinions such as “beautiful” or “professional” unless those words are part of the intended message. Write in the language of the page and use the name of a person only when identity is relevant and appropriate.

Keep descriptions aligned with the page claim. If a photo is evidence of a project, say what the project shows. If the image is a portrait, identify the person and role when that helps the reader. If the image is a product, name the model or variation needed for a choice.

Handle text, charts and complex visuals

Text inside an image can be inaccessible to someone who cannot see it or enlarge it. Put essential words in nearby HTML text, a caption or an equivalent accessible element. The alternative text can point to the purpose, but it should not be the only place where a detailed instruction or offer exists.

Charts and diagrams need more than a visual label. Give a short alternative that states the main conclusion and provide the underlying data or a longer explanation nearby. “Sales by quarter” identifies a chart but does not communicate whether sales grew, fell or stayed level.

Maps, process diagrams and infographics also need an accessible route to the same decision. The alternative does not need to reproduce every pixel; it needs to make the relevant relationship, direction, option or result understandable.

Describe functional images and links

When an image is a link or button, describe the action or destination rather than the appearance. A logo linking to the homepage might need “ChatBuild homepage” as its accessible name. A magnifying-glass icon should say “Search” if it is the search control. A product thumbnail linking to details should identify the product and destination.

Avoid duplicate announcements. If a linked image sits next to a text link to the same destination, the image can often be decorative or the two can be combined into one accessible link. Repeating the same title twice creates extra work for screen reader users.

Check states and changes. If an icon indicates unavailable, selected, expanded or secure, the accessible name or surrounding text should communicate that state. A description that remains “calendar” after the control becomes “close calendar” is misleading.

Create a useful review routine

Make image descriptions part of publishing, not a last-minute SEO task. During content review, ask what each image contributes, whether its purpose changed and whether the alternative duplicates nearby text. Keep decorative images quiet, informative images concise and complex images supported by data or explanation.

Do not stuff keywords into descriptions. Search visibility is not improved by repeating a phrase in every image, and keyword-filled text makes pages tiring for assistive technology users. Use a relevant term only when it naturally names the subject, product or destination.

Review old pages after redesigns, product changes and new campaigns. A description written for a previous image may become inaccurate when the crop, subject or page message changes.

Sources

• Images Concepts · W3C
• Decorative Images · W3C
• Image best practices · Google Search Central

Frequently asked

What should alternative text describe?

Describe the information, subject or function the image contributes to the page. Focus on what a visitor needs to understand or do rather than every visual detail.

When should an image have empty alternative text?

When it is genuinely decorative and adds no information or function. This allows assistive technology to skip it without losing meaning.

Should image descriptions contain keywords?

Only when a keyword naturally describes the subject, product or destination. Do not repeat keywords for SEO; it makes descriptions less useful.

How should a chart be described?

State the main conclusion briefly and provide the underlying data or a longer explanation in accessible text nearby.