Mapbox GL JS is an open source library for modern interactive maps, powered by WebGL. Developed for more than 3 years, it combines a variety of sophisticated algorithms, smart ideas and novel approaches to deliver 60fps rendering of vector data with thousands of shapes and millions of points. In this talk, you will find out how it works under the hood and why it's so challenging to build dynamic WebGL applications. The talk will cover scalable font rendering, line and polygon tessellation, in-browser spatial indexing, collision detection, label placement, point clustering, shape clipping, line simplification, sprite packing, efficient binary data encoding and transfer, parallel processing using Web Workers and more!