PDFs are traditionally rendered using native code plugins. Often enough those native code viewers turn into unintentional native code execution platforms. I will talk about Mozilla's new PDF.js pure JavaScript PDF render. Flashy demos aside I will in particular focus on performance tricks we use to make rendering fast (we just-in-time compiler PDF content!), and report on limits of the canvas API, and how we plan to fix those since we conveniently also make a popular browser: Firefox. Have you heard of it? Less