SPY (the broad S&P 500) and QQQ (the tech-heavy Nasdaq 100) are closely correlated, so watching them together intraday is a cheap edge. Which one is leading, and whether they agree, reads the character and conviction of the current move.

What leadership tells you

When QQQ leads a rally (making new highs first, pulling back less), the move is risk-on and tech-driven — often a stronger, more momentum-y advance. When SPY leads or holds up while QQQ lags, the move is broader or more defensive. The leader is where the conviction is; trading the laggard toward the leader (SPY catching up to a stronger QQQ) can be a continuation play.

Divergence as a warning

When they diverge — SPY making a new high while QQQ fails to, or vice versa — the move lacks agreement and is suspect, much like an A-D line divergence. A SPY rally that QQQ won't confirm is a caution flag: the two usually agree, so disagreement often precedes a stall or reversal. It's a fast, two-chart breadth check.

SPY and QQQ agreeing = a move with conviction. One leading, one lagging = information. One diverging = a warning.

How to use it

Keep QQQ on a side chart as confirmation and a leading tell for SPY scalps: take SPY longs with more confidence when QQQ is also strong, and tighten up when QQQ diverges. Use the leader to anticipate the laggard. It's context, not a trigger — a cross-check that a SPY move has intermarket backing, best paired with the dealer map and the regime.