A 5,000-contract print on the same strike can mean two very different things. Read the structure, not just the volume. If you are learning how to read options flow, this is the first distinction worth making.

The block

Negotiated between two parties, often through a broker. Prints at midprice or close to it. Frequently part of a hedged package - the long option leg is offset by stock or futures. The block is positioning, not urgency. It often does not move the underlying because the dealer side is hedged in real time.

The sweep

Aggressive multi-venue execution. The trader took out the offer across exchanges. They paid the spread and accepted market impact. They wanted in now.

Why the read is opposite

A block is often hedging or structured exposure. A sweep is almost always a directional decision with a clock attached. Treating them as the same volume signal misses 80% of the information. The sweep vs block options question is not academic - it changes what the print means.

Sweep vs block options: the practical filter

Sweep + OTM + same-month expiry: directional bet, short-dated. High signal.
Block + ATM + dated long: structured exposure or hedge. Low directional signal.
Sweep + ITM + long-dated: someone wants delta exposure in size. Moderate signal.
Block + OTM + dated short: lottery ticket or risk reversal leg. Read context.

Where most retail screeners fail

Generic 'unusual volume' alerts treat sweeps and blocks identically because they are both 'large.' The information value is completely different. Separating them surfaces the trades that actually carry directional conviction.

Once you know how to read options flow at the structure level, the next two filters are ratio and venue. The Vol/OI ratio separates real conviction from routine volume, and the dark pool connection shows where the stock leg is hiding. Both show up in the options flow and unusual options activity views.