# hash The block’s identifying hash — always exactly 32 bytes in internal (kernel) byte order. ``` let hash: Data ``` ## Discussion Internal order is the byte-reversed inverse of the display-order hex shown by block explorers. To render for humans, wrap this in [`BlockHash`](/documentation/BitcoinKernel/BlockHash) and read [`description`](/documentation/BitcoinKernel/BlockHash/description). The hash is stable across any chain state that doesn’t orphan this specific block, which is why the whole [`BlockSource`](/documentation/BitcoinKernel/BlockSource) protocol uses hashes (not heights) to address blocks.