# BlockchainSync.Update A single snapshot of sync progress — the element type emitted by [`BlockchainSync.Updates`](/documentation/BitcoinKernel/BlockchainSync/Updates). ``` struct Update ``` ## Overview Each `Update` captures the sync engine’s state at one moment: lifecycle phase, local chainstate tip, and the source’s best tip as of the most recent [`bestTip()`](/documentation/BitcoinKernel/BlockSource/bestTip()) call.