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Cloud saves are keyed by slot. Data is an opaque string — serialize it yourself, usually as JSON. The platform stores the payload and tracks its version for you.

Read

LoadResult:

Write

You do not pass a version. The platform assigns the next one and returns it.

Multiple slots

Slots are independent — use them to separate concerns that change at different rates.

Concurrency

Writes are applied inside a server-side transaction, so two sessions writing the same slot cannot corrupt each other — the later write wins and gets the higher version. The SDK does not surface a merge hook. If your game can run in two tabs at once and you need last-write-wins to be smarter than that, read before writing and merge in your own code.

Limits

  • 500 KB per slot
  • Payloads above the limit are rejected server-side

When a write fails

success is false. Common causes: payload too large, the player’s session expired, or the shell stopped responding. Keep the unsaved state in memory and retry rather than discarding progress.