0DTE and the Gamma Landscape: Trading Expiration Day with Positioning Context

Zero-days-to-expiry options have rewritten the intraday volatility profile of index names. The same mechanics that make them cheap to trade — rapid decay, high leverage near the money — make their aggregate hedging footprint enormous precisely when it matters most: at the close, at the strikes, on the day everything comes due.

Why 0DTE concentrates gamma

An option's gamma peaks when it is near the money and near expiry. A 0DTE chain is all near-expiry by definition, so strikes near the spot price carry outsized hedging weight. As spot migrates through the session, the strikes with the largest 0DTE open interest become the market's most active hedging zones — which is why 0DTE days show both the tightest afternoon compression and the sharpest end-of-day acceleration.

The two regimes of an expiration day

The morning often starts compressed: long-gamma hedging chops the tape between the heavy strikes. The interesting question is whether the session holds that character. A break of a heavily positioned strike with participation can flip the regime — hedging that was dampening starts amplifying, and the afternoon travels twice the morning's range. The gamma flip is where that change is most likely to be estimated; the heavy strikes are where its effects concentrate.

Keeping the risk honest

0DTE punishes unfocused risk-taking. A few disciplines that positioning context supports:

• Size to the invalidation, not the hope. With expiring options, define the level where the read is wrong before entry; the decay clock leaves no time to be vague.
• Respect the concentration strikes. A 0DTE trade placed just beyond a massive open-interest strike is a trade against the hedging machinery; placed on the near side, it trades with it.
• Watch participation at contact. Compression ending on expanding volume through a heavy strike is the regime-change signature. Compression ending on nothing is usually just noise.
• Plan for the close. Hedging pressure peaks into expiration; the last hour is where positioning effects are strongest and where stops are most expensive to be wrong about.

Context, again, not prophecy

None of this predicts direction. It maps where the machinery is dense, which conditions are confirming, and which levels change the character of the day. That is the entire job of positioning analysis in a 0DTE session: not to call the close, but to keep you from learning how expiration works through your own account statement.