The heatmap is a grid: strike price down one axis, time of day across the other, and colour intensity showing how much open interest sat at that strike at that moment. An option chain tells you where positions stand right now. This tells you where they were built, when they were built, and when they were taken off, which is a different and usually more useful question.
Vertical bands of intensity are strikes that held open interest across the whole session. Those are the walls, and they are where option writers have committed capital to the underlying not settling past them. A band that brightens through the afternoon is fresh writing arriving at that strike. A bright band that fades is positions being cut.
The fading band is the more informative of the two and the one a static chain cannot show you. Writers closing out a strike they had been defending often precedes the underlying moving through it, because the people with the strongest interest in that level holding have just stopped holding it. Watching a wall come down in real time is a different signal from observing that it was never there.
Colour encodes concentration, not direction. A bright cell says many contracts are open at that strike; it does not say whether calls or puts dominate, and it certainly does not say who is long and who is short. Every open contract has a buyer and a seller. Read the heatmap alongside the per-strike call and put split, or the two together will invite a directional conclusion the data does not support.
The support-and-resistance reading is also softer than it is usually presented. Heavy open interest genuinely does tend to pin price in quiet markets, and it genuinely does fail on news. It describes where the market has positioned, not where the market must go.
Intraday, when you want to know whether a level is being defended or abandoned, and in the last hour before expiry, when pinning effects around heavily written strikes are strongest and the grid makes them obvious.
It means that strike was carrying a large amount of open interest at that point in the session. Colour encodes concentration, not direction: a bright cell tells you many contracts are open there, not whether calls or puts dominate and not who is on which side. Read it alongside the per-strike call and put split.
The option chain is a snapshot: it shows where open interest stands right now. The heatmap adds the time axis, so you can see where positions were built and when they were cut. A strike that quietly accumulated open interest all morning and a strike that spiked in the last thirty minutes look identical in a chain and completely different here.
Not reliably. Heavy open interest marks a level that writers have committed capital to defending, which is why such strikes often act as support or resistance in quiet markets. It is a soft effect, not a rule, and it breaks on news. The more useful signal is a heavily written strike being unwound, which often precedes price moving through it.
Analytics only. Not investment advice. Last updated .