Building a Flutter App That Works Offline — A Complete Guide

Offline-first isn't just a buzzword — for field apps, retail tools, and travel products it's a requirement. We built a Flutter app that stays usable without a connection and syncs cleanly when back online. Here's how we approached caching, conflict resolution, and architecture.

Local-first data

We chose SQLite with drift for local storage and defined a clear sync boundary: which entities are cached, which are read-through, and which must always hit the network. Every mutation writes to local storage first and is queued for sync. The UI reads from local only, so the app feels instant and works offline.

Sync and conflicts

We use last-write-wins for simple fields and merge strategies for lists (e.g. append-only activity). Critical records get conflict-resolution rules and optional server-side checks. We version entities and send deltas to the backend; the backend responds with accepted versions and any server-side changes so the client can reconcile.

What we'd do again

Investing in a single source of truth (local DB) and treating the network as an optional sync channel paid off. We also added a simple sync status indicator and retry logic so users know when data is pending. If you're building a Flutter app for unreliable networks, start with the local model and add sync on top.