How 0DTE Changed the Options Market

Zero-days-to-expiration options — contracts that expire the same trading day they’re traded — were a fringe product a decade ago. Today they’re the dominant flow in the most liquid options market on earth. That change happened fast, and it reshaped how intraday markets behave in ways most retail traders still haven’t fully adjusted to.

What is 0DTE?

0DTE literally means “zero days to expiration.” It refers to an options contract that expires at the end of the current trading day. You can buy it at 9:31 AM and it’s done by 4:00 PM ET.

These contracts exist because the major index options (SPX and SPY in particular) now have daily expirations. Every Monday through Friday, new weekly contracts come into existence and old ones expire. On any given day, there’s always at least one contract expiring that day — which means there’s always 0DTE.

For individual stocks, true 0DTE is rarer because most equities still have weekly or monthly expirations. But for index products, 0DTE is now an everyday reality.

The timeline

The 0DTE explosion didn’t happen overnight. Here’s the short version:

• Before 2005— Most equity options expired monthly. Weeklies didn’t exist. Intraday expirations were unheard of.
• 2005 — The CBOE introduced weekly options on SPX, giving traders a shorter-dated product than the standard monthlies.
• 2016 — SPX expanded to Wednesday expirations in addition to Friday. This was the first time there were multiple weekly expirations on the same product.
• 2022 — SPX added Tuesday and Thursday expirations. Now there were five expirations per week — one every single trading day. For the first time, every session had its own 0DTE contract.
• 2023-2024 — Volume exploded. 0DTE grew from a small sliver of total options volume to roughly 45% of SPX volume by late 2024.
• 2025-2026 — 0DTE became the dominant flow. On most trading days it now exceeds 50% of SPX volume. On high-volatility sessions it can top 60%.

In roughly three years, zero-days-to-expiration went from “interesting new product” to “the single biggest driver of intraday flow in the world’s most liquid options market.” That is extraordinary for a capital markets product.

Why traders love them

0DTE options caught on for very practical reasons:

• No overnight risk.The position is either closed or expired by the end of the day. You don’t carry anything into the next morning.
• High leverage for small moves. With only hours until expiration, at-the-money options cost very little. A $5 move in SPX can turn a $50 option into a $500 option. The gamma is extreme.
• Clean event trades. If you have a view on a Fed announcement or CPI release, 0DTE lets you express it without holding vega exposure through the event that would otherwise crush your premium.
• Premium selling strategies. On the other side, traders who prefer to collect theta find 0DTE attractive because premium decays to zero in a single session — an entire normal week of theta harvested in one day.

What changed for everyone

Even if you never personally trade 0DTE, the existence of all this daily expiring volume has changed the market you’re trading in. A few effects:

• Intraday volatility is spikier. 0DTE positions have very high gamma concentrated around current price. Every move triggers aggressive dealer rebalancing, which can accelerate the move further.
• Reversals happen faster. When a 0DTE position unwinds (gets closed by the trader or hedged out by the dealer), the flow can reverse quickly — which is why midday dumps and late-day rips have become more common.
• Pinning is more dynamic.With new OI building every morning and expiring every afternoon, the “key strikes” shift day by day instead of being set monthly at OPEX.
• Overnight moves matter less.Intraday flow now dominates. What happened at last night’s close sets a baseline, but the day’s structure gets rewritten in real time.

The static OI problem

Here’s the punchline for gamma analysis: 0DTE flow is structurally invisible to tools that rely only on end-of-day Open Interest.

A 0DTE position that opens at 10:30 AM and closes at 3:45 PM contributes zero to tonight’s OI print. From the perspective of any tool that rebuilds the gamma surface from daily OI snapshots, it’s like those five and a half hours of dealer hedging pressure never happened.

They obviously did happen. Price moved. Volatility shifted. Structural levels were created and destroyed. But the OI-based map doesn’t show any of it. It shows the same static picture from last night’s close — now over a day old while the dominant half of the market has moved on.

This is the exact problem GammaFlux was built to solve. By combining overnight OI with live options chain data and live futures volume, the model estimates how dealer positioning is shifting in real time — including the 0DTE flow that never touches OI. For the full explanation, see why real-time gamma matters.

What it means now

Understanding 0DTE isn’t optional anymore. Even if you only trade weekly or monthly expirations, you’re trading in a market where half the flow is coming from contracts that didn’t exist at the close and won’t exist at the next open.

Three practical implications for every intraday trader:

1. Don’t trust morning-only data.Whatever map you’re using, if it’s not updating during the session, it’s probably missing the most important driver of today’s price action.
2. Expect faster reversals. The market is no longer structured for slow, patient moves. Reactive liquidity is the norm.
3. Respect the magnetism around high-volume 0DTE strikes.Even though those strikes don’t carry over to tomorrow, their dealer hedging during the session is very real. Price can get pulled toward them and then released once the positioning closes out.

0DTE options didn’t just give traders a new product. They changed the underlying structure of the options market itself. The sooner you read that change into your trading, the fewer surprises you’ll have.