Open interest, or OI for short, refers to the total number of outstanding contracts. You can refer to the open interest of a specific option contracts, or the open interest for an equity as a whole.

Open interest values DO NOT update intraday.

The open interest value DOES NOT differentiate between bought or sold options: ANY open contract will be counted towards OI.

New open interest values will be disseminated market wide during the premarket of any given trading session.  These updates will generally be completely by around 730 AM EST, at which point open interest values for all contracts will be available to view. 

Incorrect open interest values can be sent out market wide. These incorrect values will correct themselves the follow session. Click here for more information. 

Open Interest Resources:

The contracts with the highest changes in open interest can be viewed using the Open Interest Change Feed

The Contract Look Up page displays historical volume and open interest data

An analogy for Volume and Open Interest on Twitter

Tracking whales using Volume and Open Interest on Youtube