What is Aggressor side (bid / ask)?
What Is Aggressor Side in Options Flow?
Updated 2026-07-22
Quick answer
Aggressor side estimates who crossed the spread: prints at or above the ask often look like aggressive buying; at or below the bid, aggressive selling. Mid is ambiguous.
Also called: trade side, hit the bid, lift the offer, above ask, below bid.
Visual explainer
Aggressor side infers who crossed the spread, hit bid vs lift ask, feeding sentiment and side filters on the tape.
Full definition
Side is inferred from print price versus the bid/ask, not from a named account. It feeds sentiment labels (call/put plus side) and can be wrong on wide spreads, locked markets, or multi-leg packages. Treat side as a lean. Confirm with size, DEX, and structure.
How it shows up in TradingFlow
- Option Trades
Filter side: Above Ask / Ask / Mid / Bid / Below Bid, and sort/scan with sentiment columns.
How to read it
- Prioritize above-ask call buys or below-bid put buys when hunting urgency.
- Treat mid as lower confidence.
- Large mid blocks may still matter, open chain context.
Who this is for
Flow traders who filter the tape by aggressor side instead of treating all volume as equal.
Common mistakes
- Equating “at ask” with guaranteed long stock.
- Ignoring multi-leg packages that print one aggressive leg.
Frequently asked questions
- What does sentiment mean in TradingFlow?
- Sentiment combines call vs put with aggressor side into a bullish, bearish, or neutral lean, a shorthand, not proof of portfolio intent.
Related terms
- Option flowOption flow is the time-and-sales stream of options prints: contract, size, premium, and inferred aggressor side.
- Unusual options activity (UOA)UOA flags contracts or underlyings trading far above recent norms in volume, size, or premium. It is an attention screen, not a directional signal.
- Options sweepA sweep is a large order filled across multiple exchanges in rapid succession, usually to grab available liquidity quickly.
- Options block tradeAn options block is a large single print, or same-second aggregate, sized well above typical retail clips.
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