How to Write Alt Text for Images Without Guessing

Direct Answer

Write alt text by deciding what job the image does on the page, then describing only the detail a reader needs for that job. An informative image needs the useful visual detail. A functional image needs the action or destination. A decorative image may need empty alt text. A complex image usually needs a short alt text plus nearby visible explanation.

Practical Steps

Start from the page context instead of the image file name. The same photo can need different alt text on different pages.

• Write the page purpose in one sentence
• Mark each image as informative, decorative, functional, or complex
• Name the detail that matters to the reader in this context
• Avoid unsupported claims, SEO stuffing, and repeated surrounding text
• Use empty alt text only when the image is truly decorative in context
• For charts, maps, diagrams, or dense screenshots, add nearby explanation when one sentence is not enough

Example

A useful review line connects image purpose to page context.

Image: balcony herb planter
Purpose: informative
Page context: beginner herb garden setup
Alt text: Small balcony planter with basil, mint, and labeled starter pots
Avoid: Do not call it a perfect setup or mention plants not visible

Limits

This is writing guidance, not a formal accessibility audit or legal compliance review. Final alt text should be checked against the real page, product requirements, image rights, surrounding copy, and any accessibility process your team follows.

Common Mistakes

A common mistake is writing every alt text as a literal object label, such as "image of lamp", without explaining why the image is on the page. Another mistake is stuffing keywords into alt text. Good alt text should help the reader understand the page, not act like hidden promotional copy.