Why it matters
A block is the opposite of a sweep. Where a sweep grabs whatever is available across exchanges, a block is one large fill at one price, usually because the size was too big to work through the public order book without moving it. Institutions use blocks to put on positions quietly, and the print only becomes public once it is done.
That makes blocks a window into deliberate, sized positioning rather than urgency. A block does not tell you the buyer was in a hurry. It tells you they wanted a lot of a specific contract and found a counterparty willing to provide it at one price. Combined with the side token, the volume against open interest and the next morning's open interest, a block can show you a new position being established in a size that no retail order book could absorb.
The Options Flow feed labels each print Sweep, Block or Split, and the Exec filter isolates blocks so you can watch only the negotiated size.
Block vs split
A split is a large order filled in pieces on the same exchange, worked over time to reduce its impact on the price. It shows up in the feed as Split. A block is one print; a split is one order in several prints; a sweep is one order across several exchanges at once. All three describe how an order was executed, not whether it was bought or sold. The side token carries that.
What it does not tell you
- A block is not a directional signal by itself. Many blocks are hedges, rolls, or one leg of a spread. A put block at the bid can be an investor selling puts to fund something else, not a bearish bet.
- The price is not always the market. Blocks are negotiated, so the fill can sit at the bid, at the ask, or between them, and the side token reflects where it printed against the quote at that moment.
- It does not tell you if the position is new. Only the next morning's open interest can confirm that. The Robinflow flow row shows it as Open Interest next day.
- Size is relative. A block in an index product can be routine hedging. The same premium in a small-cap name is a different story.
What it looks like in the data
At 11:02 am on September 10, 2026, a single print of 10,000 QQQ put contracts crossed the tape at the bid.
Exec: BLOCK. One print of 10,000 contracts at $21.17 at 11:02:22 am ET with QQQ at $710.94. Open interest on the contract was 8,493 before the print and 19,249 the next morning. Not a recommendation.
| Column | Value | How to read it |
|---|---|---|
| Exec | BLOCK | One negotiated print |
| Side | B | Seller hit the bid |
| Premium | $21.17M | 10,000 contracts × $21.17 × 100 |
| Volume / OI | 10,036 / 8,493 | The block alone exceeded the existing open interest |
| Next-day OI | 19,249 | Open interest more than doubled the next morning |
Read together: a very large put order sold at the bid, in one piece, on a strike 3% below the market, and confirmed the next morning as a new position. Whether that was an investor collecting premium, a fund hedging, or one side of a larger structure, the row cannot say.
