How Can I Measure the Success of a Coupon Campaign?

Measure three things: how many people saw the offer, how many claimed a code, and how many used it at checkout. Gleam covers the first two. Your store or analytics covers the third.

Your Captures list shows Impressions, Conversions and Conversion Rate for each Capture, and the Capture's Leads report lists everyone who signed up. If you're running a Coupon Capture, use individual codes, so each claim can be matched to a sale later.

Check orders that used each code in your store's discount report. If you use Google Analytics 4, send the code in the coupon parameter of your purchase event, and GA4 can report revenue by coupon:

gtag("event", "purchase", {
  transaction_id: "T12345",
  value: 50.00,
  currency: "USD",
  coupon: "SAVE10"
});

Divide redemptions by claims. A popup with lots of claims and few redemptions is giving codes to people who weren't going to buy. Compare that rate across Captures and devices, and keep the offers that turn into orders.