When to use it (and when not)

This page is the short version. For the per-feature detail, see Where datadata sits and Limitations.

A good fit today

Collaborative document apps — multiple people editing structured documents and rich text in real time, with instant local feedback.
Human + AI co-editing — an agent stages changes in a session, a human reviews a three-way preview and commits. This is the workflow datadata is being honed against.
Evolving domains — schemas are documents with their own migration history, so the data model can change while the app is running.
Apps already on Cloudflare — the production backend is a Durable Object per folder with SQLite storage; if that’s your platform, deployment is natural.
Offline-capable apps — an opt-in persistence adapter makes the write queue and document cache durable, so a reload becomes a reconnect and cached documents render while disconnected. Browser storage makes that durability best-effort, and long-offline unguarded writes replay last-writer-wins — offline work that deserves review belongs in a staged session.

Not a fit (today)

Apps needing per-field permissions. Authorization covers role rules per document type, read filtering that hides documents, scope caps for agents, and per-document app policy — but visibility is whole-document: a user sees a document entirely or not at all.
Large datasets. A folder is the authority unit and lives in one Durable Object; clients subscribe per document, but a document syncs whole (no partial replication within a document), individual documents have a size cap, and there is no event-log compaction yet.
Tabular, query-shaped data. Sync is whole-document — you can’t select or project parts of documents, and there is no query language. The supported pattern is a derived store (listen to document changes, project into another document or database, query that), but if your data is fundamentally tabular, datadata is probably not the right fit.

Not a fit (by design)

Some of the above will change; the server-authoritative model won’t. If you want decentralized authority, peer-to-peer sync, CRDTs for all data (not just text), or end-to-end encryption (which is incompatible with server-side validation), datadata is the wrong tool.

Sounds like a fit?

If your app lands in the good-fit column, get in touch — the library isn’t open source yet, but early access ahead of open-sourcing is a possibility.