The Front-End Monitoring Handbook: Track Performance, Errors, and User Behavior

A comprehensive guide to building a frontend monitoring SDK from scratch, covering three main areas: performance monitoring (Core Web Vitals like FCP, LCP, CLS, plus API timing and resource loading), error tracking (JavaScript errors, Promise rejections, resource failures), and user behavior analytics (page views, scroll depth, click tracking). The tutorial provides practical code examples for implementing data collection using browser APIs like PerformanceObserver, MutationObserver, and various event listeners, along with reporting mechanisms and optimization techniques for production environments.