Attribution method: tracking link vs coupon code vs both

The mechanism you choose decides what you can measure and what survives ad-blockers.

— Tracking link: measures clicks, supports last-click attribution, but dies to ad-blockers, cookie expiry, and "I'll buy later on desktop."
— Coupon code: immune to cookies and blockers — it works whenever the customer types it, even weeks later on another device. But it can't measure clicks, and codes leak to coupon sites that steal credit.
— Both: link for click data, unique code for cross-device + cookieless capture.

Decision rule:
— If your audience buys cross-device or far from the click then insist on a unique code.
— If the brand resists a code then push attribution window to 30+ days to offset.
— If the product gets discount-shopped then a code is non-negotiable; you'll lose link credit to coupon aggregators.

Checklist: code is unique to you, link carries sub-ID, window confirmed in writing.

Definition of done: a sale 3 weeks later on a different device still credits you.