Proof of work is the consensus mechanism that secures the Bitcoin network.
Miners compete to find a valid hash for each new block of transactions by making trillions of random guesses per second. This requires real energy and specialised hardware. A valid hash demonstrates that computational effort was expended, and it cannot be faked.
Proof of work gives Bitcoin several critical properties:
- immutability — changing the transaction history means redoing the work for every subsequent block,
- decentralisation — anyone can participate, and no central authority decides which transactions are valid,
- a predictable issuance schedule, enforced by maths rather than human discretion.
Before Bitcoin, every attempt at digital cash relied on a trusted third party. Proof of work replaced that trust with physics and economics. For a closer look at how this works in practice, see my interactive guide to Bitcoin mining.