Trading term
What is Index price?
The index price is the average spot price of an asset across several major exchanges, used as the honest reference a derivative is measured against. It underpins the mark price, the funding-rate calculation and cash settlement — and averaging across venues is what stops any one exchange's price problem becoming everyone's.
A derivative needs an answer to 'what is this thing actually worth right now?' that does not come from its own order book. The index price is that answer: a weighted average of the spot price on several large exchanges, usually with rules to drop a constituent that stops trading, wanders too far from the others, or goes offline.
Those exclusion rules are the important part. If one exchange halts, breaks, or has a flash crash, a naive average would drag the index with it and every derivative referencing it would misprice at once. Discarding the outlier keeps the reference honest — which is why the index survives events that individual venues do not.
The index is not usually what your position is liquidated against directly; that job belongs to the mark price, which is the index plus a smoothed basis. But it is the foundation both mark price and the funding rate are built on, so an index that is wrong makes everything downstream wrong too.
For example
A Bitcoin index might average spot prices from several large exchanges to arrive at $100,000. If one of them prints $92,000 during an outage, the index rules exclude it rather than dragging the reference down and liquidating traders on every venue that uses it.
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Explore Premium →Why it matters to you
Nearly everything about a derivative position — its valuation, its funding, the level it liquidates at — traces back to the index price. Knowing which exchanges a contract's index draws from tells you what a venue's own wick can and cannot do to you, and it is the difference between a derivative anchored to a real market and one anchored to a single order book.
⚠ It isn't the price on your screen
Traders often assume the price on their exchange is the price. It is one input into an average of several. During stressed conditions your venue can be meaningfully away from the index, so your position's value and your liquidation distance are being judged somewhere other than where you are looking.