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Index Price is Polymarket’s estimate of the underlying asset’s fair value. It is computed from external price feeds, aggregated to resist stale or anomalous inputs, and published every 200 milliseconds per market.

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Feed Sources

Index Price can use feeds from external sources such as:
  • Pyth
  • Chainlink Data Streams
  • Hyperliquid

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Feed Selection

The system selects different feeds based on the current market session so it can use the most accurate feed set for each market. See Market Sessions.

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Aggregation

Index Price is computed as a weighted average across the selected feeds after dropping stale prices and filtering outliers. This prevents any single stale or anomalous feed from moving the Index. The same aggregation approach is used to build the C3 candidate in Mark Price, using a separate mark feed set.