Proof of Stake (PoS)
Proof of stake (PoS) is a consensus mechanism in which validators lock up the network's coins as collateral and are chosen to propose and confirm blocks; security comes from that staked capital and the penalties for breaking the rules.
How proof of stake works
A blockchain needs a way for thousands of independent computers to agree on one history. In proof of work, miners compete with computing power. In proof of stake, validators deposit coins instead, and the protocol picks who proposes the next block, usually at random weighted by stake.
Other validators then check the block and vote on it. Once enough stake has voted for a block, it is accepted. On Ethereum, blocks become finalized after about two epochs, roughly 13 minutes, after which reversing them would require destroying a huge amount of stake.
Where security comes from
Validators earn rewards for doing their job and lose money when they do not. Provable cheating, such as signing two different blocks for the same slot, triggers slashing: part of the stake is destroyed and the validator is ejected. Attacking the chain therefore means buying and risking a large share of all staked coins.
Where it is used
Ethereum switched from proof of work to proof of stake in September 2022, an upgrade known as the Merge, which cut its energy use by more than 99%. Cardano, Solana and most newer layer 1 chains also use forms of proof of stake, often with their own twists such as delegation or a fixed validator set.
Trade-offs and criticism
Critics argue that proof of stake favors those who already hold many coins, since rewards go to existing stake. Large staking providers and exchanges can also concentrate voting power. Supporters point to lower energy use and to slashing as a stronger punishment than anything proof of work offers. Both views have merit, and the details of each chain's design matter.
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Frequently asked questions
Is proof of stake less secure than proof of work?
Not inherently. They rely on different costs: hardware and electricity versus capital at risk. Each has different attack scenarios and trade-offs.
Does Bitcoin use proof of stake?
No. Bitcoin uses proof of work, and there is no plan to change that.
Do I need to run a validator to benefit?
No. Many holders delegate their coins or use a staking pool, accepting extra risks such as fees and dependence on the operator.
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