Delta measures how much an option's price moves per $1 move in SPY — a 0.50 delta option gains about $0.50 for each $1 SPY rises. For a 0DTE scalp, delta is how you judge whether the option will track SPY well enough to be worth trading.
Why delta matters for a scalp
A scalp lives on catching a quick SPY move and having your option respond. A higher-delta option (near-the-money, delta ~0.40–0.60) moves a lot when SPY moves — responsive, and you feel the move. A low-delta option (far-OTM, delta ~0.10) barely budges on a normal SPY move (why isn't my option moving?) — you can be right on direction and make almost nothing. For scalping, responsiveness wins.
The practical target
Many scalpers favor roughly at-the-money delta (around 0.40–0.55) — responsive enough to track SPY meaningfully, liquid enough to fill cleanly, without paying up for deep-in-the-money. Higher delta = more responsive and more expensive; lower delta = cheaper and sluggish. The right balance for a scalp leans toward responsive. This ties directly to picking a strike, since delta and strike distance are two views of the same choice.
Low delta feels cheap and trades like molasses. For a scalp you want the option to move — so lean toward at-the-money delta, not the far-out lottery.
The quick takeaway
For a 0DTE scalp, target near-at-the-money delta (roughly 0.40–0.55) so the option tracks SPY responsively and fills cleanly — avoid low-delta far-OTM options that lag. It's the same decision as strike selection, and NoVo handles it automatically, favoring responsive, liquid strikes when it executes.