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Kleros is a decentralized dispute resolution protocol on Ethereum (currently running on Arbitrum One). It uses game-theoretic incentives and randomly selected jurors to resolve disputes in a trustless, affordable, and fast way.
Jurors self-select by staking PNK tokens in courts they want to serve in. When a dispute is created, jurors are drawn randomly with probability proportional to their stake. This prevents Sybil attacks while ensuring skin-in-the-game.
PNK (Pinakion) is the native token of Kleros. It serves two functions: (1) it’s used for staking to become a juror, and (2) it provides incentive alignment incoherent jurors lose PNK to coherent ones.
Jurors receive arbitration fees (in ETH) for each dispute they participate in. Additionally, jurors who vote coherently (in line with the final ruling) receive PNK redistributed from incoherent jurors.
Game theory. Jurors are incentivized to vote as they expect the majority to vote (Schelling point). Dishonest jurors lose their staked PNK, while honest jurors gain from the redistribution. The appeal system further protects against initial misjudgments.
Yes. Any party can appeal a ruling by funding the appeal cost. Each appeal round increases the number of jurors. Appeals can escalate up the court hierarchy until the General Court. This makes attacks exponentially expensive.
Jurors who fail to vote during the voting period are treated as incoherent and lose a portion of their staked PNK. This incentivizes active participation.
Kleros V2 runs on Arbitrum One (an Ethereum L2 rollup). Cross-chain disputes from Ethereum mainnet and Gnosis Chain are supported via the Vea bridge and Gateway system.
Traditional arbitration relies on trusted institutions and is expensive and slow. Kleros is decentralized (no single point of control), affordable (fees are a fraction of traditional costs), fast (days instead of months), and transparent (all evidence and votes are on-chain).
PNK holders govern the protocol through Snapshot voting. Governance proposals (KIPs) are submitted on the Kleros Forum and voted on by the community. On-chain execution uses the KlerosGovernor contract.
Jurors should not stake using a smart contract account specifically in courts where hiddenVotes are enabled, because the frontend is currently unable to verify the signature. At the moment, the courts which have hiddenVotes enabled are the General Court on Gnosis Chain and the Spanish General Court on both Ethereum Mainnet and Gnosis Chain.Additionally, when using a smart contract wallet, the receive() function may cause transfers made with .send() to fail. For example, receiving ETH juror rewards might fail. This is a known issue caused by the Berlin hardfork, as documented by Safe. The Kleros contracts deployed from 2025 rely on a SafeSend mechanism which is not affected by this limitation.