Compare Spreads

The same reading side by side across symbols.

Read median_spread_bps_underlying for the cross-symbol comparison, not median_spread: index levels differ by 4x between SPX and NDX, so their dollar widths are not on one scale.

A symbol whose chain cannot be read comes back as a row with unavailable set rather than being dropped — a missing row would read as "not compared", and a zeroed one as "perfectly tight".

puts_percentile follows the same rule as the snapshot endpoint's history: null unless the requested scope is one the daily rollup stored. The widths themselves are returned at whatever scope was asked for — this panel carries its own expiry pills, and only the ranking is scope-bound.

Beta — contract may change.