Reading OI Spurts Without the False Positives

What Actually Counts as a Spurt

The measurement is the percentage change in open interest at a single strike across a short window, read against the base that strike was carrying when the window opened. Not the change since the previous close. Not the total sitting there now. The change, over minutes, as a proportion of what was already there.

With NIFTY near 24,800, the 25000 call went from 8,20,000 contracts to 11,48,000 in a quarter of an hour. That is fresh positioning arriving in a block, at a strike 200 points above spot — and it is close to invisible if you are watching the absolute open interest column, because 11,48,000 does not look different from 8,20,000 at a glance and the strike may not even be the heaviest on the board.

Why the Percentage Threshold Is the Whole Design

Open interest bases across a single chain differ by orders of magnitude. The strike nearest spot can carry forty times what a strike a few hundred points away carries, and both carry hundreds of times what the far wings hold. A fixed contract threshold across that range screens nothing — it just returns the busiest strikes, which sorting the absolute open interest column would have found anyway.

The percentage removes the base from the comparison, and the effect is that the largest absolute change on the board is frequently not the largest event on it.

The 24800 strike added more contracts in raw terms — 4,10,000 against 3,28,000 — and it is the less interesting of the two. It is the heaviest strike on the board and it adds contracts all session; a tenth more of an already enormous base is ordinary traffic. The 25000 strike grew its position by two fifths in fifteen minutes, which is not the pace it had been running at. Sorting on the percentage puts the second one on top, and that is the entire point of the tool.

That second condition is not optional, because the design decision that makes the percentage useful is the same one that produces the tool's worst output.

The Low-Base False Positive

This is the most important paragraph in the guide. A strike sitting far out of the money, holding 200 contracts, goes to 1,400 contracts. That is a 600% spurt. It will be the largest percentage on the board, it will sort straight to the top of any percentage-ranked scan, and it means nothing whatsoever.

Twelve hundred contracts is not a position anyone builds a view around. It is consistent with a small tail hedge, a fund rolling a leftover leg, a market maker quoting into a strike nobody had quoted into all day, or one fat-fingered order. None of that is information about where the market thinks price is going, and the percentage cannot tell any of it apart.

The trap is worse than it looks, for two reasons. Placement: small bases live at the far strikes, so low-base artefacts cluster in exactly the region of the chain with the least bearing on the current session. And instability runs both ways — that same strike falling back from 1,400 to 200 prints an 86% collapse, which sorts to the top of any negative-spurt scan with equal confidence and equal emptiness.

The fix is to reverse your reading order. Look at the absolute change first and ask whether that many contracts is a meaningful position in this underlying. Only once the answer is yes does the percentage get to say anything — and what it says then is how quickly the position arrived, which is genuinely useful. Read it the other way round and the percentage will walk you to the emptiest strikes on the board, every session.

Pairing a Spurt With Premium Direction

Open interest is symmetric. Every contract created has a buyer and a writer, so the number itself can never tell you which side was pushing. What breaks the tie is what premium at that strike was doing while the contracts were being created.

If a call strike gains open interest while its premium rises, buyers were lifting offers and writers were pulled in to supply them — commonly read as a long build-up. If the same strike gains open interest while its premium falls, sellers were hitting bids and buyers absorbed them — commonly read as fresh call writing, which is where the "resistance is building here" interpretation comes from. The put side mirrors it.

That rule quietly breaks when the underlying moved during the window. Premium is not a clean signal of who was aggressive; it also contains whatever delta contributed. A call premium that rose while the index rallied tells you nothing until you compare it against how much it should have risen.

The correction runs the other way too. A call premium that fell while the index dropped 70 points is not evidence of writing at all — delta alone would have taken it down. Whichever way the underlying went, the question is whether premium beat or missed what the move accounts for, and it is the miss that carries the information.

Spurts Near Spot and Spurts Far From It

Distance from spot decides whether a build has anything to do with the session you are trading. A spurt 200 points above a 24,800 index sits at a strike the market can plausibly reach before this expiry ends — if the at-the-money straddle is pricing a move of around 223 points, that strike is inside the band being charged for. Positioning there is taken by people who expect it to be tested.

A spurt 1,700 points away is a different instrument. Those strikes are bought as cheap tail cover or sold as far-dated income; they are not positioned around this week's range. A build there may say something about how a longer horizon is being hedged. It says nothing about today.

Within that near band, strikes just beyond a level price has recently reached tend to attract genuine builds, because that is where writers set up once a level has held. Round-number strikes attract builds for a duller reason — they already carry the liquidity, so size gets done there without moving the quote. That makes round-number spurts common rather than special.

None of this is a rule about where price must stop. Concentrated positioning is a crowding observation, and a strike everyone wrote into is exactly the kind of level that moves quickly once it gives way.

Running an Absolute Filter Alongside the Percentage

The percentage threshold and an absolute floor answer two different questions, and a usable scan asks both at once. The percentage decides how fast the position arrived. The absolute floor decides whether it is large enough to be anyone's position. A strike clears both, or it does not appear.

Set two absolute conditions rather than one. A floor on the base open interest throws out strikes that were never meaningful to begin with — the low-base artefact at its source. A floor on the size of the change itself throws out small builds that happen to land on a modest base.

Those figures are starting points for tuning, not settings to copy. An absolute floor calibrated on NIFTY will silence a stock scan completely, and one calibrated on a stock lets every index artefact straight through. Set them per instrument, and reset them when an expiry cycle rolls, because open interest early in a cycle is a fraction of what the same strikes carry near the end.

One more cross-check costs nothing. Compare the open interest added against the volume traded at that strike in the same window. If the 25000 CE added 3,28,000 contracts on 3,90,000 traded, almost every contract that changed hands opened a fresh position — the flow was close to one-directional. The same 3,28,000 on 41,00,000 traded is a residue left by heavy two-way churn, and far less can be read into it.

A Spurt Is an Attention Flag, Not a Signal

Be precise about what a clean spurt establishes: somebody with size committed at that strike in a short window, and the flow was one-sided enough to leave a visible mark. That is the complete list. It does not establish that they are right, that the position will still be there in an hour, or that price will respect the strike.

Positioning comes off as fast as it goes on. A strike that added 3,28,000 contracts in fifteen minutes can hand most of them back over the next hour, and the same scanner reports that as a negative spurt of similar size. Neither print is a forecast. Both are records.

Because alerts are retained through the session, the most valuable use of the tool is retrospective. At the close, look at what price did after each flag. Doing that across a few weeks in one underlying teaches you what a spurt is worth there — which strikes held, which were run through, and how often a flag was followed by nothing at all. That last category is larger than most people expect, and knowing its size is what stops a flag from being mistaken for a conclusion.

Everything here describes where positioning went, which is a crowding observation and not a rule about price. Concentrated strikes break, sometimes violently, and usually at the moment the crowd standing on them starts to leave.