Write useful image descriptions
Identify an image’s purpose, describe the information it adds and avoid repeating captions or surrounding text without a reason.
Follow the method ↓
The answer in 30 seconds
The same photograph may provide evidence in one page and atmosphere in another. Imagine removing it: what would the reader lose? That question helps you decide what a useful description needs to convey.
Alternative text depends on the image’s role in its page. Describe the information it contributes; when an image is a link or control, describe the action or destination.
Examples to adapt
The useful information is the action and file, not the arrow’s colour.
A long description may interrupt reading without adding useful information.
Follow the method
- 1Identify the role
Separate decorative, informative and functional images. A decorative web image may need an empty alternative. Ask what a reader would lose if this image were removed from this page. The same photograph can convey information in an article and provide atmosphere elsewhere. Its alternative text should reflect that specific role rather than repeat topic keywords.
- 2Write the useful detail
Describe what matters in context without adding keyword lists. Avoid assumptions about someone’s identity or intentions.
- 3Handle complex material
For a chart, provide brief orientation and make the values or conclusion available in nearby text or a table. For a chart, identify the useful conclusion and provide its values and units in the associated content. A short alternative should not turn into an unwieldy list. Read it alongside the caption to avoid announcing the same information twice.
- 4Read the complete page
Read the heading, paragraph, alternative and caption together. Remove repetition and check that links still make sense without their images.
A closer look
Describe the image’s role in the page
The same photo can set a mood, reveal a useful detail or act as a link. Alternative text depends on its purpose and surrounding text.
| Situation | Example approach | Check |
|---|---|---|
| Purely decorative photo | Empty alternative if no useful information is lost | Does nearby text already suffice? |
| Photo showing a useful detail | Describe the detail needed for understanding | Is the information available without the image? |
| Image alone inside a link | Name the destination or action | Is the link understandable? |
| Complex chart | Short alternative with a nearby detailed description | Are data and conclusions available as text? |
The W3C decision tree distinguishes decoration, information and function. Photo credits and licensing remain separate from alternative text.
Should every alternative start with “photo of”?
Start with useful information. Identify the image type when it affects interpretation, such as distinguishing a reconstruction from a documentary photograph. Avoid repeating an already accessible caption word for word.
Supporting documentation : W3C WAI — An alt Decision Tree · Consulted on 2026-10-15. Examples and calculations are illustrative.
A checklist to keep
Use these checks to record your observations. They are a reading aid, not an automatic assessment.
| Check | What to examine | Action |
|---|---|---|
| Decorative | No additional information | Empty alternative |
| Informative | Relevant detail | Concise description |
| Functional | Action or destination | Useful label |
| Complex | Data and interpretation | Associated text or table |
Read the checklist directly in the table.
What to check
Context determines the description.
Visible captions and alternatives may have different purposes.
Do not describe details you cannot establish.
Common questions
Should I start with image of?
Usually you can go straight to the useful information.
Can an alternative contain an entire chart?
Put lengthy explanations in accessible nearby content.
Sources and documentation
Documentation consulted on . Examples are illustrative; interfaces and results may change.
Choose an image alternative by its role
A text alternative depends on what the image contributes. Appearance alone is insufficient when it acts as a button or conveys data.
- Define the role
- Write the equivalent
- Read without the image
| Situation | What changes | Useful check |
|---|---|---|
| Informative image | Convey the essential information in context. | Do not unnecessarily repeat a nearby caption. |
| Functional image | Name the action or destination. | A button should announce its purpose, not just its icon’s shape. |
| Complex chart | Provide a complete equivalent of useful data or relationships. | Supply a description and, where appropriate, a readable table. |
An empty alt attribute avoids announcing a purely decorative image. Read the page without images: essential actions and information should remain identifiable.
Documentation : W3C WAI — Images Tutorial ↗ · · Read the reference record →