Plyr is a widely-used, client-side JavaScript library that provides a simple, accessible, and customizable media player for HTML5 video/audio, YouTube, and Vimeo. It is implemented as a modular class with plugins, utilities, and a comprehensive SCSS theming system. The library handles all aspects of media playback: custom controls, captions (VTT), fullscreen, picture-in-picture, AirPlay, speed and quality selection, preview thumbnails, and ads (Google IMA). It uses a build system based on Gulp and Rollup, produces ES and UMD bundles, and includes a polyfilled variant for older browsers. The codebase is well-organized with clear separation of concerns (controls, captions, fullscreen, listeners, storage, plugins) and extensive JSDoc documentation. However, it exhibits some technical drift, including legacy UA sniffing, a large controls module marked for refactoring, and deprecated build tooling. Despite this, the library remains actively maintained and is production-ready, with a robust demo site and a large user community.