Slashing
Slashing is a penalty in proof-of-stake networks that destroys part of a validator's staked coins and usually removes it from the validator set when it provably breaks the protocol's rules.
Why slashing exists
Proof of stake replaces the electricity costs of mining with capital at risk. For that to work, cheating must cost money. Slashing is the mechanism that makes it costly: if a validator signs messages that could help rewrite or split the chain, the protocol takes part of its stake.
Because the evidence is cryptographic signatures, anyone can prove the offense on-chain. No court or committee is needed.
What triggers it
On Ethereum, a validator is slashed for proposing two different blocks for the same slot, or for casting attestations (votes) that contradict each other. Other networks have similar rules, sometimes also punishing long downtime.
Being offline on Ethereum is not slashing. An offline validator misses rewards and pays small inactivity penalties, which are much milder. Larger penalties apply only if a big part of the network goes offline at the same time.
How much can be lost
The size depends on the chain. On Ethereum, a slashed validator loses an initial penalty, keeps losing small amounts until it exits, and pays an extra correlation penalty that grows with how many other validators were slashed around the same time. An isolated mistake usually costs a small fraction of the stake; a coordinated attack by many validators could cost almost all of it.
How honest operators get slashed
Most real slashings are accidents, not attacks. The classic cause is running the same validator keys on two machines at once, for example a backup server that starts while the main one is still active. Both sign, and the network sees a double signature.
If you delegate or use a staking pool, the operator's mistakes can reduce your stake too. Some pools and liquid staking protocols cover small losses from their own funds, but that is a policy, not a guarantee.
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Frequently asked questions
Can I be slashed if my internet goes down?
On Ethereum, no. Downtime leads to missed rewards and small penalties, not slashing. Rules differ on other chains, so check the specific network.
Are slashed coins given to someone?
Mostly they are destroyed. A small part may go to the validator that reported the offense as a whistleblower reward.
Does slashing affect people who delegate?
On many chains, yes. Delegated stake can be cut along with the validator's own stake, which is why the operator's track record matters.
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