If Black-Scholes were correct, implied volatility would be identical across all strikes for a given expiration. Plot IV against strike and you would get a flat line. Instead, you get a curve. That curve encodes information the model cannot capture.

Equity skew vs. crypto smile

In equity markets, the curve is typically a skew: IV increases as strikes decrease. OTM puts carry higher IV than OTM calls, reflecting persistent demand for downside protection from portfolio hedgers.

In BTC options on Deribit, the shape depends on sentiment. During rallies, call IV can exceed put IV as speculative demand for leveraged upside flows into the market. During sell-offs, the pattern inverts toward the equity-like skew. These shifts happen faster than in traditional markets because the participant base is more speculative and less structurally hedged.

Implied Volatility Strike Price 40% 60% 80% 100% 64k 66k 68k 70k 71k Equity skew BTC 0-DTE ATM (spot) IV > 100% Deep OTM puts IV ~ 52% ATM level Hedge zone: too expensive at 0-DTE

The 25-delta risk reversal

A useful summary statistic is the 25-delta risk reversal:

$$RR_{25} = \sigma_{25\Delta\, \text{call}} - \sigma_{25\Delta\, \text{put}}$$

A negative value means puts are more expensive (bearish skew). A positive value means calls are (bullish). Tracking this over time reveals shifts in market sentiment before they show up in spot price.

Smile dynamics when spot moves

This is where it gets practical. When BTC drops 0.3%, does the IV at your put strike stay the same (sticky strike), move with the delta level (sticky delta), or follow the moneyness ratio (sticky moneyness)?

From my work analyzing 0-DTE put pricing on Deribit, BTC behaves as a mix of sticky strike and sticky delta for small moves. For larger moves driven by volatility events, the smile shifts more aggressively. The local smile slope $d\sigma/dK$ becomes the key parameter: it determines how much your IV changes when spot moves, which in turn determines your actual P&L versus what the constant-IV Greeks predict.

Multi-expiry signals

Comparing the smile across expirations reveals the market's time structure of fear. If the near-term smile is steep but the 3-month smile is flat, the fear is seen as temporary. If both are steep, the concern is structural. I use these signals when deciding whether conditions favor entering a hedged position: a steep near-term skew with flat long-term skew suggests elevated but transient risk, which often means expensive short-dated puts and no valid entry for the hedging framework.