0DTE Options & Gamma Exposure:
What Every Trader Must Know

What Are 0DTE Options?

0DTE stands for "zero days to expiration." These are options contracts that expire on the same calendar day they are traded. At open, you buy or sell an option. By 4:00 PM ET, it's settled — worth its intrinsic value or zero.

For SPY, 0DTE options have become ubiquitous. SPY now has daily expirations — every single trading day, a fresh batch of options expire at the close. This wasn't always the case. Before 2022, weekly SPY expirations (Monday, Wednesday, Friday) were the closest thing to 0DTE. Now, every day is expiration day.

The audience for 0DTE options includes a wide range of participants: retail day traders attracted by the leverage and defined risk, hedge funds running intraday gamma strategies, institutions selling covered calls on a daily basis, and algorithmic traders exploiting the extreme gamma dynamics unique to same-day expiration contracts.

Why 0DTE Options Have Extreme Gamma

To understand why 0DTE gamma is so extreme, you need to understand the relationship between time and gamma. Gamma is highest for at-the-money options, and it increases as expiration approaches — in an accelerating, non-linear fashion.

The reason is intuitive: with 30 days left, an at-the-money option has substantial time value. A $1 move in SPY changes the option's delta, but there's still a lot of time for price to move back. The option's sensitivity to that $1 move is moderated by the time premium buffer.

With zero days left, there is no time value buffer. An ATM 0DTE option is essentially a binary bet: will SPY close above or below this strike? The delta moves violently with every tick of SPY because the probability of being in-the-money shifts dramatically with every price change. A $0.50 move in SPY can change a 0DTE option's delta by 0.20 or more. That rapid delta change — that's extreme gamma.

How 0DTE Gamma Affects Intraday Price Action

When large volumes of 0DTE options are open at specific strikes, the dealer hedging flows from those positions create structural forces throughout the trading day. These forces are not subtle — they can drive significant intraday moves.

Here's how it plays out:

1. Morning open: New 0DTE options are written or bought. Dealers establish initial hedges based on opening price and option strikes relative to spot.
2. Mid-session: As SPY moves, dealers continuously rehedge. Large 0DTE call positions above current price create selling pressure as price rises (call delta increases, dealers sell). Large 0DTE put positions below create buying pressure as price falls (put delta increases in magnitude, dealers buy).
3. Final hour: Gamma is at its peak. Minor moves in SPY trigger massive hedging flows. This is when 0DTE intraday patterns become most pronounced — sharp intraday reversals, sudden range expansions, and pinning behavior near large OI strikes.
4. Close: All 0DTE positions are settled. The hedges are unwound. This creates Market-on-Close (MOC) imbalances that can cause sharp moves in the final 5-10 minutes of trading.

The 0DTE Volume Explosion — Why It Matters

The scale of 0DTE trading has grown to the point where it is no longer a niche activity — it is the market. By volume, 0DTE options now represent approximately 50% or more of all SPY options traded on a given day. On active trading days around macro events, that number is even higher.

What does this mean structurally?

• Systemic dealer hedging: Dealers are managing enormous intraday gamma books that must be rehedged continuously. The flows from 0DTE hedging are now large enough to move SPY price on their own — not just react to it.
• Intraday volatility patterns: The 0DTE gamma cycle creates recognizable intraday patterns — specifically, a tendency for volatility to spike in the final hour as gamma explodes near expiration.
• Regime interaction: 0DTE gamma can temporarily override the structural regime set by multi-week options. A day with extreme 0DTE call positioning can suppress intraday moves even if the underlying GEX is negative, because the 0DTE dealers are locally long gamma on the day's chain.

Using DTE Filters on GEXBoard

Because 0DTE gamma is so different in character from longer-dated gamma, GEXBoard lets you slice the GEX profile by expiration range. This is essential for different types of analysis:

A common workflow: check "all expirations" at the start of the week to understand the macro structural picture (where are the durable walls?), then switch to "0DTE only" at the open to see where today's intraday gamma is concentrated. If the 0DTE Call Wall aligns with the multi-week Call Wall, that's a very strong structural level for the day.

0DTE Gamma Around Key Strikes — The Pinning Effect

The pinning effect is one of the most well-documented phenomena in 0DTE options markets. When a strike has large 0DTE open interest, price tends to be drawn toward it as expiration approaches. The mechanism:

• If SPY is below the large OI strike: dealers with long gamma exposure from that strike will buy as price rises toward it, adding upward fuel
• If SPY is above the large OI strike: dealers sell as price falls toward it, adding downward pressure
• Near the strike: the delta of the 0DTE option swings violently, requiring constant rehedging that creates a gravitational effect on price

In practice, you'll see SPY oscillate around a large 0DTE strike multiple times in the final hour, as the extreme gamma makes it very expensive for price to stray too far from the strike while hedging flows bring it back. Round number strikes (e.g., SPY 590, 595, 600) tend to have the largest 0DTE OI concentration, making them the strongest pin targets.

The Risk of 0DTE for Market Structure

The same mechanics that make 0DTE useful for analysis also create potential risks in market structure:

Gamma Unwind at Close

When all 0DTE positions expire worthless or are closed near end-of-day, dealers must unwind their hedges. If the day had a large directional 0DTE position (say, massive call buying), dealers were short a lot of SPY shares to hedge. When those calls expire, dealers must buy back those shares — creating a sharp late-day rally. Conversely, a large put day means dealers must sell shares at close as their short hedge is no longer needed. These forced unwinds create the sharp, often confusing moves in the final 5 minutes of trading.

MOC Imbalances

The combination of 0DTE expiration hedging and normal end-of-day portfolio rebalancing creates regularly elevated Market-on-Close imbalances on heavy 0DTE expiration days. These MOC flows can send SPY 0.3-0.5% in either direction in the final minute of trading — sometimes reversing the entire intraday trend.

0DTE Trading Strategy Implications

Whether you trade 0DTE options directly or simply trade SPY, the 0DTE gamma structure shapes your intraday environment. Key implications:

• Identify the 0DTE Call Wall and Put Wall every morning: These are your intraday structural boundaries. Price will have structural resistance at the 0DTE Call Wall and support at the 0DTE Put Wall — often more reliably than multi-day levels on heavy 0DTE volume days.
• The final hour is different: Gamma explodes in the last 60 minutes. Moves that would be ordinary at 11am become violent at 3:30pm. Reduce position size or use tighter stops as the close approaches if you're not specifically playing the 0DTE dynamics.
• Macro event days override 0DTE structure: On Fed days, CPI days, or major event days, directional flows often overwhelm 0DTE gamma. Don't rely on pinning or structural walls to contain price when a major catalyst is in play.
• Avoid selling 0DTE premium near key strikes at open: The extreme gamma makes short 0DTE positions dangerous near large OI strikes — a small move at the wrong time can blow out a credit spread before you can adjust.