Your mobile app is live. Then someone asks whether there's a web version. This guide covers extending your existing Django API to serve a Next.js web app on its own subdomain — without rebuilding the backend, breaking mobile auth, or maintaining two codebases you don't have time for. Everything runs against the same Django API from Guide 01. The web app lives at app.yourdomain.com, uses httpOnly cookies instead of SecureStore, deploys to Vercel, and shares one database, one media bucket and one backend with mobile. What's inside — 31 pages When to use React Native Web vs Next.js vs both, with honest trade-offs for real situations Full subdomain architecture — root, app, api, media and support — planned before you touch DNS Every Cloudflare DNS record you need, which to proxy and which not to, and the www redirect rule React Native Web with Expo — setup, platform-specific file extensions, and the token storage problem on web Next.js with App Router — Axios client, edge middleware for route protection without flicker, security headers A custom Django auth class that accepts Bearer tokens from mobile and httpOnly cookies from web on the same endpoints Google and Apple Sign-In on web, which are completely different flows from mobile, with matching Django endpoints Vercel deployment, environment variables, and per-branch preview deployments Progressive Web App setup — manifest, service worker, and the apple-touch-icon iOS actually uses Universal Links, Android App Links, Smart App Banners, and a complete invite landing page that deep-links into your native app or falls back to the browser A 16-item web launch checklist Who this is for Mobile developers who built with the stack from Guide 01 and want a web presence without running a second backend. Guide 05 of the React Native + Django series. Instant PDF download.