1
What open interest measures
Open interest counts contracts that are open right now - positions that have been entered and not yet closed or liquidated. Every contract has a long and a short side, so OI grows only when new positions are created and falls when positions are closed. It is a stock of exposure, not a flow of trading.
- New longs matched with new shorts increase OI; closing trades between existing holders decrease it.
- OI is quoted per instrument and per exchange - the same coin can be crowded on one venue and empty on another.
- Liquidation cascades show up as sharp OI drops, because forced closes remove positions.
2
Open interest vs volume
Volume counts everything traded during a period; open interest counts what remains open at a moment. High volume with flat OI means positions are churning hands with no new commitment. Rising OI means fresh money is entering the market and staying.
- Volume is a flow over time; OI is a snapshot of live exposure.
- Rising price with rising OI suggests new longs driving the move; rising price with falling OI suggests shorts covering.
- A perp can print big volume numbers and still hold too little OI to support size.
3
How OI relates to funding and spreads
Funding rates and OI describe the same crowd from two angles: funding shows which side pays for the imbalance, OI shows how big the pool is. A high funding rate on a large, rising OI means a genuinely crowded trade with real payments behind it. The same rate on tiny OI is noise that one player can flip.
- Fast OI growth alongside extreme funding often precedes violent unwinds when the crowd exits.
- Diverging OI between exchanges on the same coin hints at localized pressure - the conditions where spreads appear.
- An OI collapse during your funding trade means the crowd is leaving and the rate is likely to normalize.
4
Using OI when sizing arbitrage positions
For an arbitrage trader OI is a filter and a sizing input, not a trigger. It tells you whether the perp you are about to short has enough open exposure to stay liquid, and whether the funding you are farming rests on a stable base or a crowd about to stampede.
- Prefer instruments where your position would be a small fraction of existing OI.
- Treat funding opportunities on very small OI as fragile - the rate can vanish with one large exit.
- Watch OI trend during multi-day funding positions; a steady decline is an early warning to reassess.
