How to choose website images and write useful alt text

Choose images for what they explain. A photograph of the actual work can answer a customer's question; a decorative stock image may only add download weight. Decide the image's purpose before writing its alternative text.

Build a short image list

For each page, record the image subject, its purpose, the file owner and permission to publish. Keep the original file and note any required credit. Do not copy a competitor's photograph or treat an image found in search as automatically available for commercial use.

Match the crop to the layout

Check the subject on both desktop and mobile. A wide crop may work on a large screen but remove the useful detail when stacked on a phone. Give the developer permission to choose an appropriate crop, or mark features that must remain visible.

Write alternatives by purpose

W3C distinguishes informative, decorative and functional images. Describe essential information for an informative image, use an empty alternative for purely decorative imagery and describe the action for an image used as a control. A chart may also need its information explained in nearby text.

Work through an example

For an illustrative photo showing a repaired window frame, a useful alternative could be “Repaired timber frame around a ground-floor window.” “Best repair service quality professional windows” does not describe the image. If the same information is already fully conveyed by surrounding text and the photo is decorative, review whether an empty alternative is more appropriate.

Check the published result

Ask the developer to review file size, dimensions and alternatives in the actual page. Turn off images or inspect the text alternative to see whether the relevant meaning survives. Make sure visible captions do not conflict with the image.

The final image list should let you identify every file's source and purpose. Keep it with the handover so replacing an image later does not accidentally remove useful information or introduce an unlicensed asset.

Practical guidance with illustrative examples. Read our editorial standards or send a correction.