Proof of History (PoH)

Proof of History (PoH) is a system that records the order of transactions. This helps a blockchain quickly determine what happened first.

What is Proof of History (PoH)?

PoH works like a digital stopwatch for a blockchain: a shared digital record of transactions. It creates a verifiable timeline before the network approves all transactions.

To do this, PoH uses a series of cryptographic calculations. Each new result builds on the previous one. This makes the order verifiable after the fact and difficult to change.

PoH is not a system that approves transactions on its own. Solana uses it together with Proof of Stake. PoH orders transactions, while validators check whether they’re valid.

An example of Proof of History (PoH)

Suppose two transactions arrive on Solana almost at the same time. PoH links each transaction to a spot on the digital stopwatch.

Anyone can then check which transaction appears earlier on the timeline. Validators don’t have to spend time discussing the order first. That saves time.

Why is Proof of History (PoH) important in crypto?

PoH is especially important for Solana. Because the order is established in advance, the network can process transactions faster and more efficiently. That’s why PoH often comes up in discussions about Solana’s speed and costs.

PoH doesn’t mean Solana processes transactions without checks. Validators still have to approve them. PoH also isn’t a full replacement for Proof of Stake or consensus: it mainly helps put transactions in order.

The technology also has limitations. Validators need powerful hardware to keep performing the calculations. This can limit the number of participants who can become validators. PoH is also relatively new, and Solana has experienced network outages in the past.