What it counts
Open interest counts the contracts still open, longs and shorts alike: each contract is one long and one short. So the figure is not the two sides added together. It is the size of what the market is holding, counted once.
Hyperliquid publishes it per market: each perpetual's asset context carries an openInterest, in units of the asset, which this site shows in dollars at the mark price so that markets of different prices can be compared.
It is a stock, not a flow, and that is the difference from volume. Volume counts what traded over a window and starts again at zero; open interest is what is still held at this instant. A market can trade a great deal and end the day with the same open interest, if every new position met one being closed.
Why it rises and falls
- It rises when a new long meets a new short. A contract that did not exist now does, and both sides of it are newly held.
- It falls when two holders close against each other. A long being sold to a short who is buying back ends the contract, and the figure drops by its size.
- It does not move when a position changes hands. A long selling to someone opening a long replaces one holder with another: the contract survives, so the count does not change.
- It stops at a cap. Hyperliquid holds an open interest cap per market, publishes the list of markets sitting at theirs, and refuses the orders that would push past it by name, as
positionIncreaseAtOpenInterestCapRejectedoropenInterestIncreaseRejected.
Reading it beside the price
On its own the figure says little; beside the price it says something. Rising with the price, it says money is coming in. The four combinations follow from the mechanics above, since open interest can only rise when positions are opened and fall when they are closed.
| Price | Open interest | What the pair is consistent with |
|---|---|---|
| Up | Up | New positions behind the rise: money coming into the market |
| Up | Down | A rise made of positions closing, shorts buying back rather than longs arriving |
| Down | Up | New positions behind the fall, opened as it happened |
| Down | Down | Positions leaving on both sides, the market emptying rather than turning |
Consistent with is not the same as caused by. The table says what the two figures can be read together as, and nothing more: open interest cannot tell you who opened, at what price, or why.
What it never says
The side. Every contract is one long and one short, so the figure is symmetric by construction. A rise says positions were opened; it never says whether the people opening them were buying or selling, nor which of the two was in a hurry.
It also says nothing about the margin behind those positions, nor the prices they were opened at. Two markets with the same open interest can be one held at 2x and one held at 20x, and the second sits far closer to liquidation. The figure is a size, not a risk.
And it says nothing about the past unless someone recorded it. Hyperliquid's API gives the open interest of the present only. Hyperkeel records it every hour, and each market page of this site draws it since that record began.
It says how much is held, not how much can be sold at this price in the next minute. The order book answers that question, and a market can carry a large open interest while its book is thin, which is exactly when a liquidation moves the price.
Open interest and funding together
The two figures answer different halves of the same question. Open interest says how much is held on a market; funding says what it currently costs to hold one side of it. A high open interest with a strongly positive funding rate describes a market where a great deal is held, and where holding long is expensive.
Both are published per market, and both move on their own: a rate can turn while the open interest stands still, and the reverse. This site shows each on its own page, market by market.
How the agent uses it
Open interest is one of the bounds the agent's universe is measured with. A market whose open interest no longer passes the bounds it was measured with is set aside for that day, by name and with its reason, before any model is asked anything.
It is also a size limit. A market is set aside when the complete ladder, sized on the day's equity, would be more than 1% of the 24-hour volume or 0.5% of the open interest. A position that is large next to the market it sits in cannot be left resting at a price and expected to fill.