Offline Mode was Notion's most requested feature for years, but building it meant solving tough technical challenges around our unique block architecture. Here's the architecture and data model that made it possible.

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Notion's engineering team explains how they built Offline Mode, their most-requested feature. The post covers the evolution of their SQLite cache into a persistent storage layer, a forest-of-trees data model using offline_page and offline_action tables to track multiple independent reasons a page should be available offline, push-based sync using page version snapshots instead of polling, and incremental reconciliation of offline trees as workspace content changes. The architecture supports offline inheritance (e.g., database pages inheriting offline status from a parent), handles edge cases like pages with multiple offline reasons, and uses a lastDownloadedTimestamp to avoid unnecessary refetches on reconnect.

How we made Notion available offline

<p>Offline isn’t a feature, it’s a system. The interesting part is the data model tracking intent (why something is offline) is what makes sync and reconciliation actually work.</p>
