Cross-Platform WhatsApp-Style Chat App

I want to launch a real-time chat application that feels as familiar as WhatsApp but removes the paywall entirely and runs everywhere—iOS, Android, and in the browser. The core experience must cover one-to-one and group messaging with the same speed and reliability users expect from a modern messenger.

No authentication is required; users should be able to open the app and start chatting instantly. If a lightweight, automatic identifier is needed under the hood (for encryption or routing), build it in transparently so the end-user never sees a sign-up screen.

Because this project targets three platforms at once, I am open to React Native, Flutter, or any other cross-platform toolkit that can compile cleanly to mobile and web while sharing a single codebase. Real-time transport and push notifications are up to you—Firebase, WebSockets, or a self-hosted solution are all fine so long as message delivery is instant and dependable.

Deliverables
• A single codebase deployed to iOS, Android, and Web
• Backend or real-time messaging service configured and documented
• End-to-end encryption or equivalent privacy measure baked in
• Build instructions and short video demo proving all three platforms work together in real time

Acceptance criteria: launch each platform, send messages between at least three devices, and experience zero sign-in friction from first launch to first message.