GSAP (GreenSock Animation Platform) is a professional-grade JavaScript animation library. It's widely regarded as one of the most robust and performant tools for creating animations on the web. It animates anything JavaScript can touch (CSS properties, canvas library objects, SVG, generic objects, whatever) and it solves countless browser inconsistencies, all with blazing speed, including automatic GPU-acceleration of transforms. It's FREE even for commercial uses as of April 2025.