Flow (Positioning Change)

Every other chart in the app shows the book as it stands now. Flow shows what changed over a window — where contracts were opened or closed while you were watching.

The figure has two panels sharing one strike axis, so a row means the same strike in both:

• Heatmap (left) — one tile per strike and expiration. Colour is that cell's share of the busiest strike in its own expiration column, not across the whole grid: gamma falls off as 1/√T, so a single scale would light up the front month and hide a large far-dated build, which is exactly what this chart exists to surface.
• Bars (right) — the same window collapsed across expirations into one total per strike. Which levels moved, regardless of tenor.

A blank tile means that strike is not listed for that expiration, or that nothing happened there — never a value of zero drawn as if it were data.

Long chains scroll inside the chart. The figure shows as many strikes and expirations as fit at a readable size, with the figure printed in every tile. Scroll, drag or swipe to move through the rest, or use the arrows at the edges; the strike and expiration labels stay in place, and both panels move together. It opens centred on spot — if you scroll it out of view, the tag at the edge (↑ 7,620) brings you back.

Crypto and US options. For crypto, exchanges publish open interest in the ticker, so every window is measured intraday. US options publish OI once a session via the OCC, so they get the daily windows only — 1D, 2D, 1W and 1M, counted in trading sessions.

For a worked walkthrough on live BTC data — puts built at every strike below spot while calls were built above it, and how to read the two metrics against each other — see the blog post Flow: Watching Positions Get Built, Not Just Where They Sit.