Show HN: SyncFlow – Privacy-Focused SMS/MMS Sync Between Android, Mac, and Web

**Show HN: SyncFlow – Privacy-Focused SMS/MMS Sync Between Android, Mac, and Web**

I built SyncFlow to sync my Android SMS/MMS messages to my Mac and web — without relying on Google Messages or any third-party big tech cloud.It runs on a dedicated server with a Node.js/Express API + PostgreSQL backend.The Android app syncs messages, contacts, and call history, and you read/send them from a native Mac app or web client. Your messages never touch Google, Apple, or any third-party cloud.Key technical decisions: - E2EE with Signal Protocol for message encryption - WebRTC for video/audio calls between devices - MMS attachments stored on Cloudflare R2 via presigned URLs - WebSocket for real-time message delivery + delivery status tracking - Firebase Auth for identity only — message data is fully separateStack: Kotlin (Android), Swift (Mac), Next.js (Web), Express + PostgreSQL (Server) What it does: - Read/send SMS and MMS from Mac or browser - Full contact and call history sync - Video and audio calling via WebRTC - File Transfer between your devices - Spam filtering and scheduled messages Free tier: 200 messages/month. Downloads: https://sfweb.app/download Would love feedback on the architecture especially the E2EE implementation and the MMS sync approach. Comments URL: https://news.ycombinator.com/item?id=47028731 Points: 1 # Comments: 0

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