How to Write Image Alt Text That Helps Accessibility and SEO
Alt text describes your images to screen readers and search engines. Missing or vague alt text shuts out visitors and wastes ranking signals. Here is how to do it well.
Reviewed by Jacob Rhinehart for Strelva's co-founder; products and operations lead responsibilities.
Alt text is the written description attached to an image. Screen readers read it aloud for people who cannot see the image, and search engines use it to understand what the picture shows. Missing alt text locks out visitors who rely on screen readers; vague alt text like "image" or "IMG_1234" is almost as bad, because it claims to describe the image while saying nothing.
Why both extremes fail
An image with no alt text leaves a blind visitor with silence. An image with generic alt text leaves them with noise. WCAG 2.2 expects every meaningful image to carry a real description, and search engines reward the same.
Step by step
- Find images that need attention. Use your audit, the media library, or a quick scan for missing or generic alt attributes.
- Sort by purpose. Content images (photos that carry meaning), functional images (a logo that is also a link), and decorative images (background flourishes) are handled differently.
- Describe what matters. Write a specific, concise description, usually 5 to 15 words. Name what is in the image and why it is there. Skip "image of" or "photo of"; screen readers already announce it is an image.
- Mark decorative images empty. Use alt="" (an empty value) so screen readers skip purely decorative graphics. Do not invent a description for them.
- Keep each description unique. Ten products should have ten distinct alt texts, not the same line repeated.
- Verify. Re-scan or run a free accessibility checker to confirm nothing meaningful is missing alt text.
A simple test
Read the alt text aloud with your eyes closed. If you still understand what the image is doing on the page, it is good. If it tells you nothing, rewrite it.
Frequently asked
What business owners ask next.
Should every single image have alt text?
Every meaningful image should. Purely decorative images should have an empty alt value (alt="") so screen readers skip them. The mistake to avoid is leaving the attribute off entirely, which makes screen readers read the file name.
Is keyword-stuffing alt text good for SEO?
No. Write a natural, accurate description. If a relevant keyword fits honestly, fine, but stuffing keywords reads as spam to search engines and is useless to screen-reader users.
I have hundreds of images. How do I catch up?
Prioritise images on high-traffic pages and above the fold first. You can use AI tools to draft descriptions in bulk, but review each one; automated alt text is often generic or wrong.