Optimistic oracle
Optimistic oracles are fast and cheap because most answers don't need voting — just a dispute window.
Prediction Markets 101 editorial team Updated April 16, 2026 1 min read
Definition
An optimistic oracle is a system that assumes proposed answers are correct unless disputed. UMA's oracle, used by Polymarket, is an optimistic oracle.
Plain-English explanation
The mechanism: (1) someone proposes an answer with a bond, (2) dispute window opens, (3) if nobody disputes, answer stands, (4) if disputed, escalates to token-holder vote. Economically, dishonest proposers lose bonds; honest disputers earn rewards. Equilibrium favors correct answers.