Options volume is the number of contracts traded today; open interest is the total number of contracts outstanding. Together they measure a strike’s liquidity and activity.

Volume: today's activity

Volume counts how many contracts changed hands today — a measure of current activity and interest. High volume means an active, liquid strike right now, with tighter spreads and easier fills. It resets each day.

Open interest: total outstanding

Open interest counts all contracts currently open (not yet closed or expired) — a measure of the total positioning at a strike. High open interest at a strike is what creates the dealer walls and pins — it’s the standing positioning dealers must hedge.

Volume is today’s trading; open interest is the standing position. One shows activity, the other shows where the weight sits.

Why both matter

For reading a quote: high volume + high open interest = a liquid strike you can trade cleanly. For dealer structure: open interest at big strikes is what builds the levels NoVo maps. Check both when picking a strike.