Why it matters
Alt text is how people using screen readers, and search engines and AI assistants, know what an image shows. Missing alt is easy to find, but the common failures are subtler: alt="IMG_4821.jpg" from a CMS that copies the file name, alt="logo" that says nothing about whose logo, "image of" at the start (the screen reader already said image), a caption repeated word for word so it's read twice, or a linked banner with alt="" that leaves the link with no name at all.
This auditor reads the HTML and applies the W3C's alt decision tree and WCAG 1.1.1 to each image in context: whether it's inside a link or button, whether the link has other text, whether a figure caption already says the same thing, and whether the image is marked decorative. It can't see the pictures, so it won't tell you an alt is wrong for the image, but it catches the patterns that are wrong for every image.
How to use it
- View the page source and paste the HTML.
- Fix the failures first: missing alts, file names and nameless links.
- Check the warnings: repeats and overlong alts.
- Download the CSV to share with whoever writes the content.
FAQ
When should alt be empty?
When the image adds nothing a reader would miss: dividers, background textures, or a photo next to text that already says the same thing. Use alt="" (not a missing alt) so screen readers skip it.
What should a linked image's alt say?
Where the link goes or what it does, such as "Autumn sale: 20% off tables", not what the picture looks like.
How long should alt text be?
As short as it can be while doing the job, usually a sentence. Around 150 characters is a common limit; put longer descriptions in the page or a caption.
Does alt text help SEO?
Yes. Search engines and AI assistants use it to understand images, but write it for people first.
