They’re starting this as an experiment in their PDF editor, yes. They then want to extend to PDF reading, and then hope to extend to the general web browsing.
will be available as part of Firefox’s built-in PDF editor
Firefox is able to add an image in a PDF using our popular open source pdf.js library[…] Starting in Firefox 130, we will automatically generate an alt text and let the user validate it. So every time an image is added, […]
In the future, we want to be able to provide an alt text for any existing image in PDFs, except images which just contain text (it’s usually the case for PDFs containing scanned books).
Once the alt text feature in PDF.js has matured and proven to work well, we hope to make the feature available in general browsing for users with screen readers.