Proof of History (PoH) is a cryptographic technique invented by Solana founder Anatoly Yakovenko. It creates a verifiable sequence of events that serves as a historical record and built-in clock for the Solana network.

PoH works by generating a continuous chain of SHA-256 hash computations where each output is used as the input for the next. Because each computation takes a measurable amount of time, the resulting chain provides a verifiable timestamp for any event inserted into it.

PoH is not a consensus mechanism — it is a pre-processing step that allows Solana validators to agree on the order of transactions before they reach consensus. This dramatically reduces the time validators spend communicating about ordering, enabling Solana's high throughput.