How I add Polar (Merchant of Record) + Stripe to any Next.js app in 10 minutes — without an SDK

A developer explains integrating Polar and Stripe into Next.js apps by avoiding SDKs and using native fetch to prevent fetch failed errors on serverless platforms like Vercel. Separately, another guide details building a production offline-first Progressive Web App without React or Next.js. This approach utilizes Service Workers, Firebase Hosting, and vanilla JavaScript to ensure usability in areas with unreliable connectivity, allowing previously visited content to load instantly and public tools to function without network access.