Good alt text makes your slides, PDFs and LMS pages work for screen-reader users — and it's quick once you know the role the image plays. Pick the role, follow the guidance, draft, check the length. Nothing is stored or sent.
Step 1 · What is this image doing?
Informative
A photo or diagram that adds meaning
Decorative
Purely visual; adds no information
Functional
A link, button or logo that does something
Complex
A chart, graph, map or infographic
Text in image
A screenshot or graphic containing words
Pick a role above
…and you'll get tailored guidance plus a length check for your draft.
Step 2 · Draft & check
0 characters
The golden rule: describe the image's purpose in context, not every pixel. The same photo needs different alt text in a biology lecture vs a design class. Don't start with "Image of…" — screen readers already announce it's an image.
A free tool from NTLSN.com · aligned with WCAG 2.1 (1.1.1 Non-text Content) · no data leaves your browser.