Bitcoin is the best-known example of a PoW network. The computational cost makes it extremely expensive for an attacker to retroactively manipulate the blockchain, since doing so would require more computing power than the rest of the entire network combined.

The key criticism of Proof of Work is its high energy consumption: estimates suggest the global Bitcoin mining network uses as much electricity as some mid-sized industrialized countries.

Despite this criticism, PoW is considered the longest-proven and, to date, most robust security model for a decentralized blockchain, which is why Bitcoin has deliberately not switched to Proof of Stake.