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Glossary

What is alt text?

Updated:

Alt text is a short text alternative for an image, written in the img element's alt attribute, that screen readers read aloud in place of the picture. Decorative images get an empty alt.

Why it matters when you convert a PDF to EPUB

A PDF rarely carries usable alternative text for its images, and a converter cannot honestly write descriptions it does not know. The images in a converted EPUB keep whatever the PDF offers; good alt text still needs a person.

How EpubCC handles it: images extracted from the PDF are written with an empty alt attribute, because the engine has no reliable description to offer and does not invent one. A screen reader then skips them as decorative, so images that carry information, such as charts with data, need alt text added by a person after conversion.

Related terms

EPUBCheck messages about this

  • ACC-011 SVG hyperlink has no accessible name
  • ACC-009 MathML should either have an "alttext" attribute or "annotation-xml" child element.

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FAQ

What is alt text?

Alt text is a short text alternative for an image, written in the img element's alt attribute, that screen readers read aloud in place of the picture. Decorative images get an empty alt.