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Write alt text to explain an image’s purpose in its page context—not simply to list what it depicts. An informative image needs a concise account of its meaning; a decorative image needs an empty alt value (alt=""); an image that acts as a link or button needs to name its destination or action; and a complex chart or diagram needs a short label plus a fuller text equivalent.
Start by deciding what the image does on the page
The same image can need different alt text in different contexts. A photo might illustrate a point, add no information, or serve as the only content in a link. Ask what a reader would miss if the image were unavailable, and whether nearby text already supplies that information. W3C/WAI’s Images Tutorial organizes image alternatives by purpose: informative, decorative, functional, and complex.
| Image role | What the alternative should do | Typical treatment |
|---|---|---|
| Informative | Convey the essential meaning or information the image adds | A short, context-specific description |
| Decorative or redundant | Let assistive technology skip an image that adds nothing needed | Empty alt value: alt="" |
| Functional | Identify what activating the image does or where it leads | Action or destination, such as “Search” |
| Complex | Identify the graphic and provide access to its detailed information | Short alt plus a longer text equivalent |
Write informative alt text around the image’s meaning
Describe the information or meaning the image contributes to this specific page, not every visible object. W3C/WAI advises that an alternative should convey “the meaning or content that is displayed visually,” which “typically isn’t a literal description of the image” (Informative Images).
For example, if an article uses a photo to illustrate an action being discussed, describe that relevant action rather than writing a generic inventory such as “photo of people.” The right wording depends on what the surrounding article is teaching; there is no universal caption that works in every context.
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Use an empty value for decorative or redundant images
If an image is only visual styling, or its relevant information is already conveyed in nearby text, use an empty alt value: alt="". This tells assistive technology it can skip the image. Do not write “decorative image” in the alt text, and do not omit the alt attribute. W3C/WAI warns that when the attribute is missing, some screen readers may announce the image’s filename instead (Decorative Images).
<img src="topinfo_bg.png" alt="">Describe what a functional image does
When an image is the only content in a link or control, name the action or destination—not just the pictured object. W3C/WAI’s examples include “Print this page” instead of “printer,” “Search” instead of “magnifying lens,” and “Example.com homepage” instead of “Example.com logo” (Functional Images).
For a logo that links to a home page, describe that destination. If nearby link text already names the destination and the image adds no information, consider whether the image is redundant in that context. The purpose of the image within the control determines its alternative.
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1Repair Windows errors before they cause bigger problems2Fix the driver behind crashes, sound loss and screen glitches3Clear out junk files and repair common Windows errorsGive charts and diagrams a short label and a detailed equivalent
Do not try to fit all the data or explanation for a complex visual into its alt attribute. Use concise alt text to identify the graphic and its subject, then make the detailed information available in nearby prose, a data table, or another appropriate text description. W3C/WAI gives this chart-alt example: “Bar chart showing monthly and total visitors for the first quarter 2025 for sites 1 to 3” (Complex Images).
The longer equivalent should preserve the details readers need, such as values, relationships, or the main takeaway. If a paragraph below already explains the chart’s trend, avoid announcing the same trend again in the alt text. Section508.gov also advises against duplicating chart trends that are explained in nearby text (Authoring Meaningful Alternative Text).
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Keep alt text concise and avoid repeating nearby content
Use the shortest wording that still communicates the image’s purpose. W3C/WAI says alt text should be “the most concise description possible” of that purpose; when an image needs more than a short phrase or sentence, use a long-description method instead (Tips and Tricks).
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- Include the information a reader needs from the image.
- Do not repeat a caption or surrounding sentence when it already conveys the same information.
- Choose wording based on the image’s role here, rather than applying a fixed caption template.
For HTML images, the alt attribute provides the text alternative. W3C documents its use on img elements in the WCAG 2.2 technique H37.
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