Shoelace is a popular open-source user interface (UI) library that provides a collection of reusable, customizable web components designed to be framework-agnostic. With a focus on simplicity and accessibility, Shoelace allows developers to easily integrate modern, consistent UI elements into their projects without relying on specific frameworks such as React or Angular. The library includes components like buttons, forms, modals, and more, each built with native web technologies to ensure compatibility and ease of use across various projects.