What is GEX Flip?
The SPX level where dealer gamma flips sign — the regime boundary of the day.
Definition
The flip (or "gamma flip") is the SPX level at which the dealer book transitions from net positive to net negative gamma. Above flip → dealers dampen; below flip → dealers amplify. The flip moves daily as positions roll and option chains expire.
Why it matters for trading
- Crossing flip is a regime change, not a signal. Strategies that worked above flip (fade rallies) reverse below flip (chase breakouts).
- The flip is a magnetic level. Once crossed, dealers actively trade *back toward it* in positive-gamma mode — so if SPX recrosses flip from below, expect mean-reversion until the next flip recalc.
- Distance to flip in % is more diagnostic than absolute SPX level. SPX 50 points below flip = mild; 200 points below = stress mechanics, breakout risk both ways.