When you buy or sell an option, a market maker usually takes the other side — and immediately hedges by trading shares. Gamma measures how fast their hedge must change as the price moves. Summing it across all open contracts gives GEX (gamma exposure): an estimate of how many dollars of stock dealers must buy or sell per 1% move. Convention here: calls count positive, puts negative (dealers long calls / short puts).

Why care? Dealer hedging is mechanical — it happens regardless of anyone's opinion:

• Net GEX positive → dealers sell into rallies and buy dips → moves get dampened; price tends to pin near big strikes.
• Net GEX negative → hedging chases price (sell weakness, buy strength) → moves get amplified; expect faster, wider swings.

• Key level tiles — Spot (with 30-day implied vol), Net GEX (its sign = which regime you're in), Gamma flip (the price where net gamma crosses zero — the border between the two regimes), Call wall (strike with the most positive gamma — often acts as resistance / a pin magnet), Put wall (most negative — often support, but also where downside accelerates if it breaks).
• GEX by strike — where the hedging pressure sits. Tall aqua bars near spot = pinning force; heavy red bars below = fuel for a fast move down if reached.
• GEX heatmap (strike × expiry) — which expiry holds the gamma. Near-dated gamma is the strongest; after it expires (especially monthly OPEX, 3rd Friday) walls can dissolve overnight — re-check the day after.
• Net GEX vs price — a simulation: if spot moved to X, what would net gamma be? The zero-crossing is the flip; a steep curve means the regime changes quickly with price.
• Max pain — for each possible settlement price, the total dollars option holders would collect (dashed lines split calls vs puts). The minimum of the curve is the settlement price where option writers keep the most premium. Since dealers hedge toward reducing their risk, price often drifts toward max pain into expiration. Respect the expiry filter: max pain is a per-expiry concept — select the front expiry for the classic reading.
• Highest open interest — the individual contracts (strike + expiry) holding the most OI, calls vs puts. These are the strikes market makers care most about — big call OI above spot often caps rallies into expiry; big put OI below marks defended levels. Follows the expiry filter.
• Key levels over time — how spot, flip and walls migrate. Walls stair-stepping up with price is constructive; spot slipping under the flip is a volatility-expansion warning.

Say spot is $42, flip $40.50, call wall $45, put wall $38, net GEX positive:

• Between $40.50 and $45 dealers dampen moves → chop is likely; breakouts need real flow to stick.
• Rallies often stall into the $45 call wall — a natural spot to take profits or write covered calls.
• If spot loses the $40.50 flip, hedging turns pro-cyclical → moves get faster; tighten risk or buy protection before that break while implied vol is still cheap.
• A test of the $38 put wall tends to attract support first touch — but a decisive break gets slippery.
• Into OPEX, check the heatmap: if most gamma sits in the front expiry, expect these levels to weaken right after expiration.

Levels work best as context — position sizing, strike selection and timing — not as standalone signals.

It's Wednesday; the front expiry is this Friday. Select it in the Expiry filter. Say spot is $43.20 and max pain for Friday is $42, with net GEX positive (pinning regime):

• The read — into Friday there's a mechanical drift bias from $43.20 toward $42, strongest in the final day or two when gamma is largest. It's a tendency (works best on liquid names with heavy front-expiry OI), not a certainty.
• Premium seller — sell a Friday iron condor or butterfly centered near $42, or a $44/$45 call credit spread above the call wall: you're betting price stays magnetized to max pain while theta decays fastest.
• Holder of longs — if you own $43 calls expiring Friday, the pin risk argues for taking profit or rolling out before the drift and decay eat the premium.
• Confirmation — check the heatmap: if Friday holds most of the gamma, the magnet is credible; if OI is spread across later expiries, max pain for this week matters much less.
• Invalidation — a strong catalyst (earnings, macro prints) overwhelms hedging flows; and in a negative-GEX regime the pin logic inverts into acceleration, so skip the trade there.

After expiration, re-select the next expiry — max pain resets as the OI rolls.