Third-party scripts are one of the most overlooked causes of poor Core Web Vitals in Next.js applications, yet most teams don't realize the damage until Lighthouse scores start dropping. This whitepaper from Endurance Softwares breaks down exactly how analytics tags, chat widgets, ad networks, and video embeds block the main thread, delay hydration, and spike Interaction to Next Paint (INP). It covers the core next/script loading strategies (beforeInteractive, afterInteractive, lazyOnload), adva