If you're watching options flow for the first time, two order types will dominate the tape: sweeps and blocks. Understanding the difference — and knowing how to read them — is the foundation of flow-based trading.
Sweep Orders: Urgency on Display
A sweep order occurs when a buyer (or seller) sends orders to multiple exchanges simultaneously to fill a large position as quickly as possible. Instead of patiently waiting for a single exchange to fill the order at the best price, the trader is paying the ask across several venues at once.
Why Sweeps Matter
Sweeps tell you one thing above all else: the trader is in a hurry. They're willing to:
- Pay above the midpoint (the "ask" price)
- Split their order across 3-5+ exchanges
- Sacrifice price efficiency for execution speed
This urgency usually means the trader has a time-sensitive thesis. They may expect a catalyst (earnings, FDA decision, macro event) or they may have information that they believe will move the stock soon.
Anatomy of a Sweep
Here's what a typical sweep looks like on the flow tape:
| Field | Value |
|---|---|
| Symbol | NVDA |
| Strike | $140 Call |
| Expiry | 14 DTE |
| Premium | $425,000 |
| Side | Ask (aggressive buy) |
| Type | SWEEP |
| Exchanges | CBOE, ISE, PHLX, ARCA |
The fact that this order hit four exchanges tells you the buyer couldn't wait. They wanted 100% fill, immediately.
Reading Sweep Direction
- Call sweep at the ask → Bullish (buyer is aggressively buying calls)
- Put sweep at the ask → Bearish (buyer is aggressively buying puts)
- Call sweep at the bid → Potentially bearish (seller is dumping calls)
- Put sweep at the bid → Potentially bullish (seller is closing puts)
The side (ask vs. bid) matters as much as the option type (call vs. put).
Block Trades: Institutional Size
A block trade is a large, single-fill order executed at one price — usually through a negotiated deal between two institutional counterparties. Unlike sweeps, blocks don't hit multiple exchanges. They're typically filled through a broker-dealer network.
Why Blocks Matter
Block trades represent serious capital deployment. When you see a $1M+ block trade on a single strike, it usually means:
- A hedge fund is building a position
- A portfolio manager is hedging an existing stock position
- A market maker is facilitating a client order (but the client's intent is still valuable data)
How to Distinguish Meaningful Blocks
Not every block trade is a directional bet. Some are hedges, some are spread legs, and some are rolls from one expiration to another. Here's how to filter:
- Check open interest the next day — If OI increases at that strike, the block opened a new position (bullish/bearish signal). If OI stays flat, it was a closing trade or roll.
- Look at the premium relative to the stock — A $500K block on AAPL is routine. A $500K block on a $5B market cap stock is significant.
- Check the expiration — Blocks on weekly options are short-term bets. Blocks on LEAPS (6-12 months out) are strategic positioning.
- Watch for repeat activity — If the same strike/expiry gets multiple blocks over several days, someone is accumulating a position.
Sweeps vs. Blocks: Quick Comparison
| Feature | Sweep | Block |
|---|---|---|
| Speed | Multiple exchanges, fast fill | Single fill, negotiated |
| Signal | Urgency, time-sensitive thesis | Size, strategic positioning |
| Typical size | $100K - $1M+ | $250K - $10M+ |
| Visibility | Visible in real time | Sometimes reported with delay |
| Best for | Short-term momentum trades | Position-building signals |
Combining Sweeps and Blocks
The highest-conviction setups occur when sweeps and blocks align on the same name:
- Multiple call sweeps + a large call block on the same ticker in the same session → Strong bullish signal
- Put sweeps accelerating after a block put trade → Institutional hedging or directional bearish bet
- Sweep on near-term expiry + block on longer-dated expiry → The smart money sees a catalyst now and wants exposure through a longer window
Common Mistakes to Avoid
- Ignoring the side — A call at the bid is not the same as a call at the ask. Always check if the flow is aggressive buying or selling.
- Treating every large order as directional — Some blocks are hedges against stock positions. Context matters.
- Chasing flow on illiquid names — Wide bid-ask spreads make it harder to enter and exit. Stick to liquid options.
- Ignoring time decay — Short-dated sweeps lose value fast. If the move doesn't happen quickly, the trade decays.
How Profit Builders Grades Flow
Our AI evaluates every sweep and block against multiple factors — premium size, urgency, IV rank, DTE, and technical alignment — to assign a conviction grade. This eliminates the guesswork and lets you focus on the setups that historically produce the best outcomes.