What Is 0DTE?
0DTE means trading an option on the day it expires. What it is, how SPX 0DTE became 40–50% of total SPX option volume, what makes the mechanics different, and who actually trades it.
0DTE is the shorthand traders use for zero days to expiration. It means trading an option on the day it expires — usually intraday, with hours or minutes left on the contract's life. The entire arc of the contract, from listing earlier in the week (or earlier) to its final settlement, compresses into a single trading session.
The term moved from niche jargon into common usage starting in 2022, when Cboe completed the rollout of daily SPX expirations across the week. Volume followed: by 2023–2024, SPX 0DTE made up roughly 40–50% of total SPX option volume on a typical day. This article explains what 0DTE is, why it became a significant share of the market, what's economically different about it, who actually trades it, and what's specifically risky.
The mechanics, in one paragraph
Zero days to expiration — an option whose expiration is today. A contract becomes 0DTE on the trading day of its expiration. SPX has daily SPXW expirations Monday through Friday; SPY, QQQ, and IWM also have daily or near-daily expirations; the largest single-name equities have multiple expirations per week. A 0DTE option is not a special product — it's a regular weekly or daily option in its final session.
A 0DTE option wasn't necessarily listed today. Many of today's 0DTE SPX contracts were listed days earlier and have been trading the whole week. On the morning of expiration day, that contract becomes the front-month expiration on the chain. By 4:00pm ET, if it's ITM the holder receives the cash difference between SPX and the strike; if it's OTM, the contract expires worthless.
How 0DTE became a thing
Daily SPX expirations weren't always available across every weekday. Friday expirations have existed since 2005; Wednesday and Monday were added in 2016. Cboe completed the lineup in spring 2022 — Tuesday expirations launched April 18, Thursday expirations launched May 11. From mid-May 2022 onward, every trading day was someone's 0DTE.
Volume responded quickly. SPX 0DTE share of total SPX option volume grew from low single digits in early 2022 to around 40–50% by 2023–2024. The exact share fluctuates day-to-day; the trend is consistent.
A few things contributed:
- Retail-friendly characteristics. A 0DTE trade resolves in one session, so capital recycles fast and you're not holding overnight risk.
- Theta concentration. The entire time value of the contract is paid out in one day, which appeals to traders selling premium.
- Cheap directional bets. OTM 0DTE calls and puts cost a fraction of longer-dated equivalents, which appeals to traders speculating on intraday moves.
- Institutional flow. Hedgers, market makers, and short-vol strategies all participate, providing the liquidity that makes the retail flow workable.
What's economically different about 0DTE
The mechanics of options change as the time-to-expiry shrinks. Three changes drive most of what makes 0DTE distinctive. Each greek mentioned here has its own dedicated article in the Greeks module; the short definitions below are enough to read this article.
The rate at which an option loses value as time passes, holding everything else constant. Usually quoted as theta-per-day for normal options. Full coverage in Theta.
The rate at which an option's delta changes as the underlying moves. Gamma is largest for at-the-money options near expiration. Full coverage in Gamma.
The sensitivity of an option's price to changes in implied volatility, usually quoted per 1% IV change. Full coverage in Vega.
Time value compresses to zero. An option's price at any moment splits into intrinsic value (the in-the-money amount, if any) and time value (everything else). At expiration the time-value component is zero — the option is worth only its intrinsic value. Over a 0DTE session, the time-value component drains away. Theta is the speed of that drain, and on 0DTE the per-day theta number is the entire remaining premium.
Gamma is enormous near ATM. With expiration hours away, an at-the-money option's delta swings rapidly as the underlying moves. A 5000 call with SPX at 5000 has a delta near 0.5; if SPX moves to 5010, the delta might jump to 0.75 within minutes. For traders holding short ATM 0DTE positions, that delta change is the position's biggest risk — the underlying doesn't need to move much to produce a large P&L swing. We cover this in detail in Pin Risk and the Gamma Trap.
Vega shrinks in dollar terms. With less time-value left to revalue, even a meaningful change in implied volatility produces a small dollar change in the option's price. A 1-vol move in IV that's worth $0.50 on a 30-day option might be worth $0.03 on a 0DTE option. Vega still exists, but it's small compared to gamma and theta.
Who trades 0DTE and why
Four broad groups participate in SPX 0DTE markets. The labels are loose and there's overlap; this is a rough taxonomy.
Retail premium sellers. Traders running short credit spreads, iron condors, or short strangles to collect theta. The appeal is that the entire time value pays out in one session — capital recycles quickly and there's no overnight risk. The risk is the gamma side: a sharp intraday move can take a position from collecting theta to maximum loss.
Retail directional speculators. Buyers of OTM calls or puts hoping for a sharp intraday move. Premium is small in dollar terms, the percent return on a winner can be very large, the hit rate on far-OTM lottery tickets is low.
Hedgers. Funds or large positions buying cheap end-of-day downside (or upside) protection for a single trading session. 0DTE puts in particular are a low-cost way to insure a position against a sharp afternoon move that closes before tomorrow's open.
Institutional and dealer flows. Market makers providing two-sided liquidity, short-vol strategies systematically harvesting realized-vs-implied vol differences, dealer flows hedging client positions. These are the counterparties to most retail flow.
The aggregate effect is high volume and tight ATM spreads on the most-liquid expirations, which keeps the market structure functioning for the smaller retail tickets that originally drove the growth.
What's specifically risky about 0DTE
0DTE comes with risks that don't exist (or are smaller) on longer-dated options:
Gamma can move a position fast. For short ATM options on 0DTE, a small move in the underlying produces a large move in P&L. The position can go from neutral to maximum loss in under an hour. We cover the mechanism in Pin Risk and the Gamma Trap.
Small premium can hide big risk. A short credit spread that collects $0.50 of premium might have $4.50 of max loss. The risk-per-dollar-of-credit is high — much higher than on a typical longer-dated trade. Traders new to 0DTE sometimes underweight this because the absolute premium feels small.
End-of-session behavior is different. Quoted size, fill quality, and trader behavior all shift near the close. The Final 30 Minutes article covers this in detail.
Slippage is a larger percentage of expected value. When the trade's edge is $0.50 of premium, paying $0.05 round-trip in slippage takes 20% of your edge. On a longer-dated trade with $5.00 of expected value, the same slippage is 2%. This compounds across many trades.
Where this guide goes next
A roadmap for what's coming:
- The Greeks module covers what makes 0DTE pricing behave the way it does — delta, gamma, theta, vega, plus the second-order greeks (charm, vanna, volga) that matter specifically near expiration.
- The Strategies module walks through the trades themselves: credit spreads, iron condors, butterflies, long-option directional plays, and a few less common structures.
- The 0DTE Dynamics module covers what's specifically different about expiration day mechanically — pin risk, the charm greek, final-30-minute behavior, position sizing.
Key takeaways
- 0DTE means trading an option on the day it expires. The whole life of the contract resolves in a single session.
- SPX has daily SPXW expirations Monday through Friday. SPY, QQQ, IWM, and the largest single-name equities also have daily or near-daily expirations.
- Three things change as time-to-expiry approaches zero: time value compresses to zero, gamma grows enormous near ATM, vega shrinks in dollar terms.
- Four broad groups trade 0DTE: retail premium sellers, retail directional speculators, hedgers, and institutional / dealer flows.
- The specific risk of 0DTE is that there's no time for a losing position to recover. Plan exits before you enter.