Glossary
Inactivity Leak
An Ethereum proof-of-stake mechanism that gradually drains the stake of offline validators when the chain stops finalizing, so the active set can regain the supermajority needed to resume finality.
The inactivity leak is a recovery mechanism in Ethereum's proof-of-stake consensus that activates when the chain fails to finalize for more than four consecutive epochs. Finality requires validators controlling at least two-thirds of the staked ETH to attest, so if too many go offline at once — for example during a large network partition — the chain can stall indefinitely without intervention.
To break the deadlock, the protocol begins slowly reducing the effective balance of validators that are not attesting, while active validators keep their stake. Over days or weeks the offline set is diluted until the remaining online validators once again represent a two-thirds supermajority, at which point finalization resumes. Unlike slashing, the leak only penalizes inactivity and stops immediately once the chain finalizes again, letting Ethereum heal from major outages without permanent central coordination.