# BlockTreeEntrySnapshot An owned snapshot of a [`BlockTreeEntry`](/documentation/BitcoinKernel/BlockTreeEntry)’s data — three fields (height, block hash, block header) captured as Swift-owned values. ``` struct BlockTreeEntrySnapshot ``` ## Overview Unlike [`BlockTreeEntry`](/documentation/BitcoinKernel/BlockTreeEntry) (a view type whose pointer lifetime is tied to [`ChainstateManager`](/documentation/BitcoinKernel/ChainstateManager)), a snapshot owns all its data and is safe to store indefinitely, pass across tasks, and capture in closures. Used primarily by kernel notification callbacks ([`blockTip`](/documentation/BitcoinKernel/NotificationCallbacks/blockTip), [`blockConnected`](/documentation/BitcoinKernel/ValidationInterfaceCallbacks/blockConnected) etc.), where the underlying C pointer is only valid during the callback invocation. Promote any `BlockTreeEntry` to a snapshot before escaping the callback scope.