Progressive Web Applications (PWAs) are modern frontend architectures designed to provide a similar user experience as native iOS or Android apps. Built using HTML, CSS, and JavaScript, PWAs can run in browsers, be installed on devices, and function offline. However, monitoring these applications presents unique challenges for frontend engineers, including cross-browser compatibility testing, service worker performance monitoring, and testing the offline experience. To address these challenges, developers should ensure their PWA is compatible across browsers using feature detection and monitor cross-browser compatibility with error tracking and RUM tools. Service worker activity and cache performance can be evaluated by tracking key page performance metrics and comparing them across service worker and non-service worker sessions. Finally, synthetic testing can be used to validate the offline version of a PWA during development, ensuring its reliability and performance.