A 24-hour last-touch attribution layer that survives browsing before checkout

What was happening

The commerce site needed to capture utm_source, utm_medium, utm_campaign, utm_content, gclid, and fbclid. Attribution should be last-touch: a newer valid marketing visit replaces the previous snapshot. If no order is placed within 24 hours, the old attribution must expire instead of following the customer indefinitely.

Why the obvious solution was not enough

The behavior had to work for guest and logged-in browsing, survive normal navigation, and make the current attribution available when the cart or order is created. Stale data also needed active cleanup so an expired campaign was not accidentally reused.

How the solution works

1. Read only recognized marketing parameters from the landing URL and ignore ordinary query parameters that do not represent attribution.
2. When at least one valid marketing parameter is present, create a new attribution snapshot with a captured timestamp and expiry timestamp.
3. Store the snapshot in session state for the current browser flow and a cookie so normal navigation or a short return visit can recover it.
4. Treat a newer valid marketing visit as the new last touch instead of merging two campaigns into one ambiguous record.
5. Synchronize the current valid attribution into the cart or order metadata layer used by the commerce platform.
6. Before reading a saved snapshot, compare the current time with its expiry. Remove expired session, cookie, and cart values rather than returning stale data.
7. Verify order association separately from browser storage. Capturing a UTM value is not useful if it never reaches the final order record.

const MAX_AGE = 24 * 60 * 60 * 1000;

function isValidTouch(touch) {
  return touch && Date.now() - touch.capturedAt < MAX_AGE;
}

if (hasMarketingParams(location.search)) {
  saveTouch({ ...readMarketingParams(), capturedAt: Date.now() });
} else if (!isValidTouch(loadTouch())) {
  clearTouch();
}

What should be verified before shipping

• Capture each supported UTM and click ID independently as well as in a full campaign URL.
• Visit again with a different valid campaign and confirm it replaces the previous last-touch snapshot.
• Confirm ordinary navigation without campaign parameters does not erase a still-valid touch.
• Simulate the 24-hour boundary and verify expired session, cookie, and cart attribution is removed.
• Test guest and logged-in order flows and confirm the final order contains the expected valid attribution values.
• Ensure a purchase does not accidentally reuse an older expired campaign after the order or cart state changes.

What changed

Attribution became a defined piece of commerce state with a clear owner, replacement rule, and expiry instead of a loose set of URL parameters that might or might not survive until checkout.

Reusable lesson

Attribution is state management. Define when the state is created, what replaces it, how long it is valid, and exactly where it becomes part of the order.