Why Open Interest is Meaningless for 0DTE Options

The Difference Between Volume and Open Interest

In traditional options trading, Open Interest (OI) is a critical metric. It tells you how many contracts exist that have not yet been closed, exercised, or expired.

Volume tells you how many contracts traded hands today.

If you buy a 30-day option to open a new position, today’s Volume goes up by 1. Tomorrow morning, the Open Interest will also go up by 1.

The 0DTE Paradox

0DTE options are a unique beast. By definition, a 0DTE option on the SPX (for daily expirations) did not exist as a 0DTE yesterday, and it will not exist tomorrow.

Therefore, when the market opens at 9:30 AM, the Open Interest on newly listed daily 0DTE strikes is effectively zero.

Focus on Intraday Volume

Many beginner traders look at the options chain at 9:45 AM, see an Open Interest of 0, and assume the contract is illiquid. This is a mistake.

For 0DTE trading, you must ignore Open Interest entirely and look exclusively at Intraday Volume.

The true liquidity of a 0DTE contract is dictated by how many thousands of contracts are crossing the tape right now. Millions of 0DTE SPX contracts are traded every single day, created and destroyed in a single session without ever registering as overnight Open Interest.