Proof of Stake (PoS)

Proof of Stake (PoS) secures a blockchain by having validators lock up, or stake, their own cryptocurrency as collateral rather than burning electricity on computational puzzles. The protocol then picks a validator, weighted by the size of their stake, to propose the next block, while other validators check and attest to it before it becomes final.

Because a validator's own coins are at risk, PoS builds in a direct economic penalty for dishonesty: propose a fraudulent block or go offline too often and a portion of the stake can be destroyed, a process known as slashing. This aligns incentives without requiring specialized mining hardware, letting anyone with the minimum stake, or a share in a staking pool, participate in securing the network.

Ethereum switched from Proof of Work to PoS in its 2022 Merge upgrade, cutting the network's energy use by more than 99% almost overnight; its validators must deposit 32 ETH to run independently, though pooled and liquid-staking services let smaller holders join with less. Other major chains take different approaches: Cardano's Ouroboros protocol skips slashing entirely, relying on game theory instead, while Solana is only now rolling out programmatic slashing after years of relying on lighter penalties.

PoS is faster and far more energy-efficient than Proof of Work, but it raises its own concerns, including the tendency for large holders to accumulate disproportionate influence and the technical complexity of running a validator without accidentally triggering a slashing penalty.