Zero gamma (gamma flip line)

Zero gamma, also called the gamma flip line, is the specific price level where a ticker's net gamma exposure crosses from positive to negative, or back the other way. It isn't a fixed number. It moves every session as the options chain rolls, new strikes open, and existing positions expire or get closed. Finding it requires the full GEX profile across every strike, not just the number at the current spot price, since it's defined by where the running total changes sign rather than by any single strike's reading.

Think of it as a regime boundary, not a price target. Above the flip line, dealers are net long gamma and their hedging tends to sell rallies and buy dips, which compresses volatility and makes mean-reversion setups more reliable. Below it, dealers are net short gamma, and the same hedging mechanism buys strength and sells weakness, amplifying whatever direction price is already headed. The distance between spot and the flip line is itself informative. A market trading right on top of its flip line is one push away from a regime change, while one trading well above or below it has more room before the hedging character shifts.

The flip line can't tell you whether price will actually reach it, and it says nothing about what catalyst might move price there. It's also backward-looking, in the sense that it's built from the current chain: a large new options order can shift its location before the next recompute. And it's a single line summarizing a much more granular strike-by-strike picture. Two tickers can share the same flip line level while having very differently shaped gamma profiles on either side of it.

Take a ticker trading at 102 with its flip line sitting at 98. As long as price stays above 98, the positive-gamma regime holds and moves tend to stay contained. If a piece of news knocks the stock down to 97, it has now crossed into negative gamma territory. Dealer hedging that was previously dampening the decline starts adding to it instead, which is a common mechanism behind why a stock can gap through a level and keep falling with little resistance, rather than finding support where a chart pattern alone might suggest it should.