# init(hash:height:timestamp:) Creates a [`BlockTip`](/documentation/BitcoinKernel/BlockTip). ``` init(hash: Data, height: Int, timestamp: Date? = nil) ``` ## Parameters `hash` Exactly 32 bytes in internal (kernel) byte order. Passing display-order hex bytes here will make the tip compare unequal to every kernel-produced tip. `height` The block’s height above genesis (≥ 0). `timestamp` The block’s header timestamp, or `nil` when unknown. ## Discussion> Precondition: `hash.count == 32`. Wrong-length hashes crash rather > than silently truncate — this is a programmer error, not a runtime > condition callers can recover from. ```swift BlockTip(hash: Data(repeating: 0, count: 32), height: 0) // genesis placeholder ```