PolyTerminal
Where it comes from
The index draws on outside feeds, among them Pyth, Chainlink Data Streams and Hyperliquid. The exchange combines them as a weighted average after stale prices and outliers are dropped, so one stale or strange feed cannot move the index alone. The system picks different feeds depending on the market session; for instance, it can use primary venue feeds in regular hours and after-hours feeds overnight. A session changes which feeds are used, not the margin or liquidation rules.
What uses it
The funding calculation measures how far the order book has drifted from the index, and funding is what keeps the perpetual's price anchored to it. The mark price is built around the index too: its first candidate is Index + EMA(Mid - Index), where Mid is the midpoint of the best bid and best ask and EMA is an exponential moving average, and each candidate falls back to the index when its own data is missing. If the book is empty, nothing has traded recently and no outside mark feeds are available, the mark simply follows the index.
A common mix-up
The index price is not a traded price and it is not the price used for margin. It describes the underlying asset, while the mark price describes the perpetual contract. The mark price guide shows how the index, the mark and the last price relate.
Sources and checks
Every rule quoted in this article comes from the registry below. Each row names the official page and the day it was compared with the text.
All 6 rules used in this article
| Rule | Value | Official source | Checked |
|---|---|---|---|
| What the index price is | Polymarket's own estimate of what the underlying asset is worth | docs.polymarket.com/ | |
| Index price publication interval | 200 milliseconds | docs.polymarket.com/ | |
| Index price feed sources | Pyth, Chainlink Data Streams and Hyperliquid | docs.polymarket.com/ | |
| How the index is combined | a weighted average after stale prices and outliers are dropped | docs.polymarket.com/ | |
| Feed selection for the index price | different feeds depending on the market session | docs.polymarket.com/ | |
| Mark candidate C1 | Index + EMA(Mid - Index) | docs.polymarket.com/ |
Related terms
Read the full guide
Perps · 6 min
Perps Mark Price vs Index Price vs Last Price
The three prices of a Polymarket Perps market: how the index and mark prices are built, why liquidation uses the mark price and what sessions change.
PolyTerminal is an independent interface for Polymarket and is not operated or endorsed by Polymarket. Orders placed through PolyTerminal carry PolyTerminal’s Polymarket builder code, and PolyTerminal may charge a builder fee on top of Polymarket’s own fees. This page is educational and is not investment advice. Rules were compared with the official documentation on Oct 19, 2026; check the source before you act on a number.