What Is the “Nothing at Stake” Problem in PoS and How Is It Addressed?

The "nothing at stake" problem is a theoretical issue in early Proof of Stake designs where, in the event of a chain split or fork, a validator has no economic disincentive to validate on both chains simultaneously. Doing so costs them nothing extra but doubles their potential rewards.

This behavior can prevent the network from reaching a clear consensus. Modern PoS protocols solve this by implementing "slashing." If a validator is caught signing blocks on multiple competing chains, their staked collateral is destroyed, creating a significant financial penalty and ensuring they have "something at stake."