They support form filling and we will describe them in more detail below. The other two layers are the Annotation/AcroForm layer and the XFA form layer. It contains span elements that are transparent and line up with the text drawn below them on the canvas. The first layer, the text layer, enables text selection and search. PDF.js sends them to the main thread and draws them on an HTML5 canvas element.īesides the canvas, PDF.js potentially creates three more layers that are displayed on top of it. The parsed document will then generate drawing instructions.

To understand how we added support for forms and tagged PDFs, it’s first important to understand some basics about how the PDF viewer (PDF.js) works in Firefox.įirst, PDF.js will fetch and parse the document in a web worker. Below we’ll describe how we implemented the form support, improved accessibility, and made sure we had no regressions along the way. While we invested more time in the PDF viewer, we also went through the backlog of work and prioritized improving the accessibility of our PDF reader for users of assistive technologies. We decided it was time to reinvest in the PDF viewer (PDF.js) and support filling PDF forms within Firefox to make our users’ lives easier.

Firefox supported displaying PDF forms, but it didn’t support filling them: users had to print them, fill them by hand, and scan them back to digital form. Last year, during lockdown, many discovered the importance of PDF forms when having to deal remotely with administrations and large organizations like banks.

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