UMA oracle

UMA runs two versions of its optimistic oracle for different kinds of requests. In Optimistic Oracle v2, a protocol asks a question and outside proposers answer it, a model for prediction markets, sports betting and insurance. In Optimistic Oracle v3, a protocol asserts a fact itself and others can challenge it, which suits cross-chain bridges and the verification of transactions.

Each request names a reward, the bond a proposer must post and a minimum challenge period. A single request can be answered only once and disputed only once. If nobody disputes the answer before the period ends, the proposer receives the reward and gets the bond back. According to UMA, 99.8 percent of requests resolve this way without any dispute.

A disputer posts a bond of its own, and the question moves to the Data Verification Mechanism, the vote of staked UMA tokens. Voting runs in rounds of a 24-hour commit phase and a 24-hour reveal phase, and a dispute must be at least four hours old to enter a round. A dispute resolves when at least 65 percent of the staked UMA is cast for one answer, and the side that was right receives part of the losing bond.

Stakers who do not vote, or who vote against the majority, lose part of their stake to the majority voters. Unstaked tokens become free only after a waiting period of one week. Large holders of UMA can therefore weigh heavily in a vote, and manipulation by large holders was one of the concerns behind a change for Polymarket in 2025.

Polymarket opens a request in the UMA oracle every time it creates a market, and the proposed answer settles the market once the challenge period has passed. Before August 2025, anyone could propose an answer, and early or careless proposals often lost their bond and delayed markets by up to four days. On August 12, 2025, UMA introduced managed proposers: an integration sets a whitelist of addresses that may propose, while anyone can still dispute.

For Polymarket, an address qualifies with more than 20 proposals in the past three months and an accuracy above 95 percent, and 37 addresses met that standard at launch. A disputed Polymarket question still goes to the vote of UMA stakers in the Data Verification Mechanism.

DefiLlama counted $365 million in value secured by UMA across nine protocols in September 2026. Besides prediction markets, the Across bridge uses UMA assertions to confirm that a transfer reached the destination chain before it repays the relayer who fronted the funds. Insurance protocols and custom derivatives are further uses that UMA names for its oracle.

UMA crypto usually means the UMA token of the UMA protocol, an optimistic oracle for questions that need a verified answer onchain. Holders stake UMA to vote on disputed answers and on upgrades of the protocol.

A Polymarket dispute starts when someone posts a bond against a proposed answer during the challenge period. The question then goes to a vote of staked UMA tokens that takes at least 48 hours, and the side that wins receives part of the losing bond.

Since UMA introduced managed proposers in August 2025, only whitelisted addresses can propose answers to Polymarket questions. Anyone can still dispute a proposed answer by posting a bond during the challenge period.

In v2, a protocol asks a question and outside proposers answer it, which is the model behind prediction markets. In v3, a protocol asserts a fact itself and others only step in when they think it is wrong, which suits bridges.

UMA token holders vote on disputed answers from the oracle, on DAO proposals and on UMA Improvement Proposals, called UMIPs. Stakers who skip a vote or vote with the minority lose part of their stake to the majority voters.