You control it
Switch from Lovable to Bolt, from Netlify to Vercel, or to your own server: repoint the DNS and the store app follows. On a platform subdomain, a move means a new store version and users on old versions see a dead page.
Four reasons
Deep links need it
Universal Links (iOS) and App Links (Android) tie the app to a domain where you host the association files. Magic-link emails from Supabase open in the app only when the link domain is yours.
Review optics
An app that loads "id-preview--abc.lovable.app" raises questions; "app.yourbrand.com" does not. Reviewers do not forbid platform domains, but a professional URL removes a reason to look twice.
Email and OAuth consistency
Google OAuth consent screens, Sign in with Apple return URLs and transactional emails all show the domain. One domain everywhere means fewer configuration mismatches.
Set it up (20 minutes)
Works the same for every builder; the menu names differ slightly.
Register a domain
Any registrar. A subdomain of an existing domain (app.yourbrand.com) is perfect and free if you already own the brand domain.
Add the domain in your builder
Lovable: project settings → Domains. Bolt/Netlify: Domain management. v0: Vercel → Settings → Domains. Replit: Deployments → Settings → Domains. Base44: app settings → custom domain.
Set the DNS records
Usually a CNAME for the subdomain (or A records for a root domain) exactly as the builder shows. TLS certificates are issued automatically once DNS resolves.
Update the auth and email settings
Site URL and redirect URLs in Supabase/Firebase/Clerk, the OAuth client in Google Cloud, the return URL for Sign in with Apple, and any hard-coded links in emails.
Put the custom domain into WebViewGold
Config.swift / Config.java or the Cloud Builder. Redirects from the old subdomain keep working, but the app should load the final domain directly.
Host the association files
Add /.well-known/apple-app-site-association and /.well-known/assetlinks.json to your project's public folder when you enable Universal Links and App Links.
Preview and tunnel URLs are never OK
lovableproject.com previews, Replit's replit.dev workspaces, ngrok and localtunnel addresses, Vercel preview deployments: all of them disappear or sleep. An app built against one of them stops working for every user at once. The readiness check flags these domains as blockers for that reason.
Frequently asked questions
Is a platform subdomain allowed by Apple and Google?
Yes. Neither store forbids it. The reasons above are about control, deep links and professionalism, not about rules.
Can I change the URL later without a store update?
Only by redirecting the old URL to the new one on the server side, which you can do with a custom domain but not with most platform subdomains. That is the point of owning the domain.
Do I need the root domain or a subdomain?
A subdomain like app.yourbrand.com is ideal: the marketing site stays on the root domain and the app loads straight into the product.