Local-First Software

What if your app treated the user's device as a real home for their work, not just a temporary window into a remote database?

Local-First Software is a practical product-engineering guide to building applications that work offline, feel instant, sync across devices, and give users more control over their data. It explains the architecture behind local databases, change tracking, sync engines, conflict resolution, CRDTs, collaboration, privacy, backups, and production operations.

This book is for engineers, tech leads, product-minded developers, and founders who want to design offline-ready software without hand-waving away the hard parts. You will learn how to model local data, preserve user intent, handle duplicate and out-of-order sync messages, decide when the server must remain authoritative, design humane conflict UX, and ship local-first systems with testing and observability.

Inside, you will learn:

- Why local-first is more than caching
- How to choose between IndexedDB, SQLite, CRDT stores, and file-backed data
- How outboxes, operation logs, checkpoints, and tombstones work
- Why timestamps are not enough for conflict resolution
- Where Automerge, Yjs, and CRDTs fit in real products
- How to design offline UX users can trust
- How privacy, encryption, export, backup, and device recovery shape the architecture
- How to test migrations, flaky networks, old clients, and sync failures

Local-first software is not magic. It is a set of promises backed by careful engineering. This book shows how to make those promises responsibly.