# processBlockHeader(_:state:) Processes a block header for validation — runs Bitcoin Core’s [`AcceptBlockHeader`](https://github.com/bitcoin/bitcoin/blob/master/src/validation.cpp) checks without requiring the full block body. ``` @discardableResult func processBlockHeader(_ header: BlockHeader, state: BlockValidationState) -> Bool ``` ## Parameters `header` The block header to process. `state` Populated on return with the validation result. ## Return Value `true` if header processing completed successfully. ## Discussion Useful for header-first IBD patterns where headers arrive before blocks. A `true` return means the header passed initial checks (proof-of-work, timestamp bounds, version-bit activation, linkage to a known parent) — not that the block extends the best chain. Inspect `state` for a typed rejection reason on failure.