ZeptoJS is a minimalist JavaScript library for modern browsers, designed with a primary focus on providing a jQuery-compatible API in a much smaller footprint. The library is ideal for mobile web development where performance and speed are critical, and it handles most of the core functionality of jQuery such as CSS manipulation, animation, and Ajax calls with ease. Its lightweight nature (only about 10-15kb in size) makes it an excellent alternative for projects that do not require all the extensive features of jQuery. You can learn more or download the library at [http://zeptojs.com/](http://zeptojs.com/).