Slashing is a mechanism used in Polkadot and Kusama to deter malicious behavior by penalizing validators who act against the interests of the network and their nominators. Validators who engage in malicious activities might lose a portion of their staked tokens by slashing. This mechanism is essential for maintaining the security and integrity of the network, as it incentivizes validators to act in the network's best interests.


This article answers some questions regarding slashing and how nominators must know how to minimize the risks of losing part of their staked funds.


TABLE OF CONTENTS

What is slashing?


If a validator shows harmful behavior, they will be slashed, meaning they lose some of their staked tokens and all their nominators as a penalty.


If you were actively nominating that validator when the slash occurred, your stake would get slashed too. This incentivizes good behavior for validators and, at the same time, requires nominators to do their due diligence on the validators they nominate. You can be subject to slashing both when you nominate directly or through a nomination pool.

What could cause your tokens to get slashed?


Slashing will happen if a validator misbehaves in the network. This can include a validator going offline along with many others, attacking the network, or running modified software. The percentage of the stake slashed depends on the severity of the offense.


Minor offenses don't incur slashing at all. In most cases, if a validator is offline for a prolonged time (at least 4 hours on Polkadot), they will just get chilled. This means that the validator will stop validating until they fix the issue and re-declare their intention to validate.


Slashing for unavailability happens only if at least 10% of active validators go offline simultaneously, which could be an attack on the network. Misconduct that poses severe security or monetary risk to the system or mass collusion can even lead to most or all of the stake being slashed!


You cannot avoid slashing by unbonding after the offense occurred. The unbonding period is 28 days on Polkadot (and 7 days on Kusama). During the same period, the slash remains unapplied, and a governance proposal can be made to reverse it. Unless the community decides to reverse the slash, it will be applied before unbonding tokens can be withdrawn.

What happens to the slashed tokens?


All slashed tokens are added to the Treasury. This way, tokens from malicious actors can be used to reward community members who actively help build the network and ecosystem.


You can read more about slashing in our Wiki.