Definition. Call-Put Delta Skew (Delta 25) is the difference between call and put implied volatility at target delta 25, published as a time series across constant-maturity tenors for the selected asset, exchange and quote currency.

Technical. Each data point is sampled from the same model-interpolated IV surface across delta and maturity, projected onto standard tenors. The skew is unnormalized and expressed directly in IV points (call minus put).

Interpretation. Positive readings mean calls trade richer than equivalent-delta puts. Negative readings mean puts trade richer than calls.