How long should alt text be?
Short enough to hear in one breath, long enough to say what the image shows. Most good alt text is one sentence.
A working range
Aim for under about 125 characters. Many screen readers handle longer text, but long strings are tiring to hear and often repeat what the page already says. This is a common guideline, not a rule written into law.
Examples
Too short: dog
About right: A small tan dog with large ears standing on a gravel road.
Too long: A photograph, taken outdoors during the daytime, showing a small dog of tan color which has very large ears and which is standing in the middle of a road made of gravel.
About right: A small tan dog with large ears standing on a gravel road.
Habits that help
- Do not start with "image of" or "picture of". The screen reader already says it is an image.
- Describe what matters in the context of the page. A product photo needs the product, color and view.
- Put long explanations, such as a chart's data, in the page text and keep the alt text brief.
- Do not stuff keywords. It reads badly aloud.
AltSweep asks for a maximum of 125 characters, removes "image of" openers, and lets you edit every proposal before saving.