Put/call skew is the difference in implied volatility between puts and calls at the same distance from price. Because indices fall faster than they rise, downside puts almost always carry richer IV than equivalent calls — a normal, positive skew. The interesting information is in how that gap changes.
What the skew is telling you
The standard measure is the 25-delta risk reversal — the IV of a 25-delta put minus a 25-delta call (the same structure as a risk reversal). A larger positive number means downside protection is being bid up: fear, hedging demand, defensiveness. A flattening skew — or one that inverts so calls bid over puts — means complacency or an upside chase.
Reading it intraday on 0DTE
On a same-day chain, skew moves with the tape. A skew that steepens as SPY sells off confirms real hedging pressure behind the move — not just noise. A skew that flattens into a rally shows traders reaching for upside calls. Watched alongside the regime, it helps you tell a fear-driven flush (which can overshoot) from an orderly grind.
Price tells you what happened; skew tells you how the market feels about what happens next. On 0DTE, that feeling shifts fast.
Where it fits the map
Skew is one layer of the dealer read, and it leaves fingerprints on structure: heavy put demand is part of what builds and defends the put wall. It's context, not a trigger — a steep skew doesn't say “buy puts,” it says “downside is being paid for, respect the floor.” NoVo surfaces skew as one tile of the full dealer-positioning read so you can weigh it without doing the math by hand.