Ser(ve) your web app with HTTPS to any device on your network (mDNS): 1. Use convenient domain names without ports (https://app.local vs http://127.0.0.1:3000); 2. Use mDNS for .local domains, so you can visit them from your phone or any other device connected to the same network; 3. Locally-trusted development certificates (read on filosottile/mkcert how to trust certificates on mobile devices). Use-cases: 1. Simulate production-like subdomains (e.g., blog.example.com, api.example.com); 2. Test cookies scoped to specific domains; 3. Preview multi-tenant routing (e.g., tenant1.example.com, tenant2.example.com); 4. Use third-party APIs that need HTTPS.