What an open-interest heatmap measures
Open interest counts outstanding contracts after clearing. Volume counts contracts traded during the reported period. A contract can trade repeatedly, so its volume is not a count of newly opened positions. Open interest does not tell you which participant owns the long side, the short side or a hedge elsewhere.
This tool groups the returned records by strike and expiration. In All mode, calls and puts at the same pair are added; the result is a combined count, not net directional exposure. Select Calls or Puts to inspect the returned type separately. Missing values are never replaced with zero.
Reproduce a cell calculation
Suppose a hypothetical strike and expiration contain a call with OI 120 and volume 30, and a put with OI 80 and volume 10. All mode displays OI 200 or volume 40. If the put’s OI is unavailable, the OI cell shows 120* and reports one missing value. That is a partial subtotal, not evidence that total OI is 120.
An explicit zero remains 0. A dash means that the metric is unavailable or that the strike/expiration pair was not returned. Select a cell by mouse, touch or keyboard to see the number of reported and missing values. A single IV number is not shown for combined calls and puts because those contracts can have different implied volatilities.
Understand the two coverage limits
The API request is capped at 250 contracts and this page does not follow additional pages. The displayed grid then selects at most 30 returned strikes nearest the available stock quote and the earliest 12 returned expirations. Without a stock quote, it uses the lowest 30 returned strikes. Neither limit guarantees that every relevant contract is present.
The grid reports its displayed strike and expiration counts. Summary subtotals use all returned records under the selected call/put filter, including those outside the visible grid. The color scale resets for the displayed metric and sample, so equally red cells on different symbols do not necessarily contain equal counts.
A large cell is not max pain or dealer gamma
The strike with the highest OI is not automatically the max-pain strike. A max-pain calculation minimizes aggregate intrinsic payout across a specified expiration under settlement and contract-multiplier assumptions; it requires more than identifying the largest cell. This heatmap does not calculate it.
Dealer gamma also requires gamma values and assumptions about which positions dealers hold. Total OI alone cannot establish that a strike will act as support, resistance or a price magnet. Treat concentration as an observation to investigate, not a forecast or execution instruction.