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What are slots and epochs?
Slots and epochs are the units of time in proof-of-stake Ethereum. A slot is 12 seconds, a chance for one randomly chosen validator to propose a block; an epoch is 32 slots, or 6.4 minutes, the period over which validators' votes are gathered toward finality.
What it means for you
A transaction can land in a block within one slot, but it is finalized only after checkpoints are confirmed, normally about two epochs, roughly 12.8 minutes. Before that a block can in rare cases be replaced; after it, reversing the block would require destroying at least a third of all staked ETH.
How it works
In every slot one validator is randomly selected to propose a block, and a committee of validators attests to it; if the proposer is offline the slot stays empty. Committees are reshuffled every epoch. The first block of each epoch serves as a checkpoint. When validators holding at least two-thirds of staked ETH vote for a pair of checkpoints, the earlier is justified and then finalized, which normally takes about 12.8 minutes.
Sources: ethereum.org: Proof-of-stake, ethereum.org glossary, ethereum.org: Gasper · checked 4 October 2026
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