Every week, the CFTC (Commodity Futures Trading Commission) publishes a report called the COT (Commitment of Traders). It shows how many gold futures contracts large traders — like hedge funds — are betting on: will gold go up (longs) or down (shorts)?
Net Longs = Longs minus Shorts. A high number means speculators are very bullish on gold. But when everyone is already bullish, who is left to buy? That's the risk.
How does it affect gold?
COT Net Longs is a momentum AND a contrarian indicator at the same time.
Rising net longs = hedge funds are buying gold = typically good for prices in the short term.
But when net longs reach very high levels, it's a warning: if too many people are already long, there aren't many new buyers left. A small piece of bad news can trigger a rush to the exit, causing a sharp gold sell-off.