The bid-ask spread is the gap between the highest price a buyer will pay (the bid) and the lowest a seller will accept (the ask). You buy at the ask and sell at the bid, so you cross that gap twice — a hidden cost baked into every round trip.

Why it exists

Market makers quote both sides and pocket the spread as compensation for providing liquidity (what market makers do). A liquid option with tons of volume — like an at-the-money SPY 0DTE contract — has a tight penny-wide spread. An illiquid strike can have a spread so wide it's an instant loss to trade.

Why it eats scalps

Scalping lives on small, frequent profits, so costs matter enormously (what scalping is). If your target is a few cents of premium and the spread is a few cents wide, the spread can swallow the whole edge. This is a form of slippage, and it compounds over hundreds of trades (slippage on 1DTE options).

The spread is the toll you pay to enter and exit. Cross it enough times on small trades and it quietly becomes your biggest expense.

Managing it

Trade liquid strikes with tight spreads, use limit orders to control your fill instead of paying the full ask, and factor the spread into whether a scalp's target is even worth taking. Smart execution — getting filled better than the naive market price — is a real, repeatable edge, and exactly what NoVo's execution router optimizes for on every fill (execution as an edge). See why 0DTE fills are hard.