Mapbox GL JS Supported is a library that determines if a browser can run [Mapbox GL JS](https://github.com/mapbox/mapbox-gl-js), a WebGL-based mapping library. It's designed for developers integrating Mapbox GL JS into web applications who need to gracefully handle browsers that lack WebGL support or other requirements. The library can be used via a script tag or with Browserify, providing a simple `supported()` method to check compatibility.