NProgress

NProgress is a lightweight JavaScript library that displays a slim progress bar at the top of web pages during AJAX requests or page transitions. Inspired by the loading indicator used by YouTube and Medium, it provides visual feedback that content is loading, improving perceived performance. NProgress works by showing an animated progress bar that fills incrementally, even when actual progress information isn't available from the underlying request. The library is framework-agnostic and can be integrated with vanilla JavaScript, jQuery, React, Vue, Angular, or any other frontend stack. It offers simple API methods like start(), set(), inc(), and done() to control the progress indicator programmatically. NProgress includes customization options for color, speed, easing functions, and positioning through CSS modifications. The library is particularly popular in single-page applications (SPAs) where traditional page load indicators don't appear, helping maintain user engagement during asynchronous operations.