Open interest
Also known as: OI
Open interest is the total number of or of a given type that are currently open, meaning they have been bought and sold to establish a position but have not yet been closed out, exercised, or expired. It is reported separately from and measures how many contracts actually still exist at a point in time, not how many changed hands that day.
Open interest rises when a new buyer and a new seller create a brand new contract between them, and it falls when an existing buyer and seller both close out their positions, netting the contract out of existence. A trade between someone opening a position and someone else closing one leaves open interest unchanged, since one contract disappears while another is created at the same time. This is different from , which simply counts the number of contracts that traded during the day regardless of whether they were opening or closing trades.
Traders watch open interest as a gauge of how much conviction and sits behind a price move. Rising prices alongside rising open interest suggest new money is entering and backing the trend, while rising prices with falling open interest can suggest the move is being driven mainly by closing out losing positions rather than fresh buying. Open interest also affects how easily a position can be entered or exited, since contracts with very low open interest tend to have wider and less reliable pricing.