How to write good alt text, with examples
Updated
Good alt text says what the image means on that page, not everything in it. Lead with the important detail, keep it to about a sentence, use the surrounding content to decide what matters, and leave out "image of". The same photo can need different alt text on different pages.
Six rules that cover most images
- Describe the purpose, not the pixels. Ask: if the image disappeared, what would the reader miss?
- Use the context. A photo of a red sofa needs different alt text on a furniture product page than in an article about interior lighting.
- Lead with what matters. Screen reader users can't skim, so put the key subject first.
- Keep it short. Usually one sentence. Put long explanations in the page.
- Skip "image of" and "photo of". Say "Screenshot", "Illustration" or "Chart" only when the format itself matters.
- Write text that's in the image. If the image contains words people need, put them in the alt.
Before and after
Product page for a rain jacket
Weak: IMG_4021.jpg
Better: Navy rain jacket with hood up, shown from the side to show the sealed zip
News article about a city marathon
Weak: Image of people running
Better: Runners crossing the Västerbron bridge during the Stockholm Marathon
Logo in the header, linking to the home page
Weak: Blue circle logo
Better: AltVision home
Bar chart in a quarterly report
Weak: Chart
Better: Bar chart: sign-ups grew each month in Q3, from 1,200 in July to 2,050 in September
Decorative wave divider between sections
Weak: Blue wave graphic
Better: (empty) alt=""
Alt text and SEO
Search engines use alt text to understand images, so accurate alt text also helps image search. Describe the image naturally and include a relevant term when it truly fits — keyword lists hurt screen reader users and don't help ranking.
AltVision lets you add custom SEO keywords before generating, and works them into the description only where they read naturally.
Writing alt text at scale
The hard part on a real site is volume. AltVision reads each image together with the headings, paragraphs and captions around it, which is the same context these rules ask you to use, and writes a first draft in any of 31 languages. Review the suggestions — the goal is a good first draft in seconds, with a person deciding what ships.
See how to add alt text in WordPress, or try the generator on the AltVision home page.
Questions
What makes alt text good?
It conveys what the image means on that page, leads with the most important detail, is about a sentence long, and doesn't start with "image of".
Should alt text include keywords for SEO?
Only when a keyword naturally describes the image. Alt text is for people first; stuffing keywords makes it worse for screen reader users and doesn't help search.
Can AI write alt text?
Yes. Tools like AltVision analyse the image and its surrounding text to draft context-aware alt text. A person should still review it, especially for images where the purpose isn't obvious.