What is options flow? How to read it, and what it cannot tell you
Options flow is the stream of option trades as they print: which contract, how many, at what price, and where that price sat between the bid and the ask. Read well, it shows where real money is committing. Read carelessly, it is a firehose of hedges, spreads and closing trades that look exactly like bets.
What one print tells you
Every print carries a contract (symbol, strike, call or put, expiration), a size in contracts, a price, and the premium paid, which is size times price times 100. A 15,000-lot of SPY 0DTE calls at $0.49 is about $735,000 of premium. The premium, not the contract count, is what makes a print large: 15,000 contracts at a nickel is a small trade.
What a print does not carry is intent. The same 15,000 calls can be a directional bet, the hedge on a short stock position, one leg of a spread, or someone closing a position they opened last week.
Bought or sold: the bid and the ask
The best single clue to direction is where the fill landed. A fill at or above the ask means the buyer was in a hurry: bought. A fill at or below the bid means the seller was: sold. Anything in between is a negotiated fill and cannot be called either way.
That last group is most of the tape. On Monday, September 28, 2026, our tape recorded 189,374 option prints across our coverage. About 22% filled at the ask and 20% at the bid. The other 58% printed between the two, and any tool that labels those bullish or bearish is guessing.
Opening or closing: volume against open interest
Open interest is how many contracts were outstanding at the start of the day. When a contract's volume today passes its open interest, most of that volume has to be new positions rather than old ones being closed, because there were not enough old ones to close. That is the cleanest free signal that someone is opening risk, not taking it off.
On the same September 28 session, 35% of prints came on contracts whose volume had already passed their open interest.
Sweeps, blocks and unusual activity
A sweep is one order split across several exchanges at once to fill fast, usually by taking every ask it can find. A block is one large trade at a single price, often negotiated. Sweeps suggest urgency; blocks suggest size that wanted a fair price.
"Unusual" usually means the size is large relative to the contract's normal volume or open interest. It is a useful filter, but unusual is not the same as directional: a large hedge is unusual too.
Where flow earns its keep: agreeing with price
On its own, one print is a weak signal. It becomes useful in agreement with something else, above all the stock's own move. We tested this on 5,785 opening-range breakouts across 296 symbols: when at least 60% of the name's options premium sat on the side of the breakout (counted only up to 15 minutes before the break, so nothing seen in hindsight), the stock reached its target first 52% of the time, against 45% when it did not.
The gamma map adds the other half: flow tells you where money is committing, and dealer positioning tells you where the market is likely to absorb or amplify the move. The two together are far more useful than either alone.
Common questions
Is options flow a buy or sell signal?
No. It shows where money traded, not why. Treat a print as a question (who would do this, and is it opening or closing?) rather than as an instruction.
What does a fill at the ask mean?
The buyer paid the seller's price to get filled immediately, which usually means they were buying. Fills at the bid usually mean selling. Fills between the two cannot be classified.
What is the difference between a sweep and a block?
A sweep is one order filled across several exchanges at once for speed. A block is one large trade at a single price. Sweeps signal urgency, blocks signal size.
Where can I see live options flow?
FlowMonkey members see the live tape with the bid and ask at each print and a drill-down for every contract. The free SPY gamma board shows the dealer map with no login.
Read premium, not contract count; the bid and ask for direction; volume against open interest for opening vs closing. Most prints cannot be called either way, and flow matters most when it agrees with the stock's move.
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