On an options chain, volume and open interest are two different counts that are easy to confuse. Volume is the number of contracts traded today; open interest is the number of contracts currently open (not yet closed or expired) (what open interest is, reading an options chain).

What each tells you

Volume resets daily and shows today's activity and liquidity — high volume means tight spreads and easy fills (the bid-ask spread). Open interest accumulates and shows how much "size" is committed at a strike — big OI marks the strikes that matter for dealer hedging and pinning (gamma walls).

The tell: opening or closing?

The relationship between them is the insight. Volume much larger than open interest suggests new positions opening (fresh conviction). Rising open interest confirms new money committing; falling open interest means positions are being closed (unusual options activity). Same volume, opposite meaning, depending on whether OI grows or shrinks.

Volume says "something happened today." Open interest says "and here's whether it's building up or winding down." You need both to read the story.

Why it matters for structure

For a trader reading dealer positioning, open interest is the more structural number — the big-OI strikes are where hedging concentrates and where price gets magnetized (pinning and max pain, reading dealer positioning). Volume tells you today's liquidity and whether the picture is changing.