Open Interest
Also called: oi
The number of option contracts currently held open at a given strike.
Open interest tells you how many contracts exist at a strike right now. High open interest usually means better liquidity (tighter bid-ask spreads and easier fills), and clusters of open interest can act as magnets or walls for the stock near expiration. Thin open interest is a warning: you may get a bad price getting in and out.
For example
A strike with 20,000 contracts of open interest will typically fill at a fair price. A micro-cap strike with 12 contracts of open interest may cost you dearly on the spread.
Related terms
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