SOP: Deduplication method — cookie vs fingerprint vs IP+UA

SOP: Deduplication method — cookie vs fingerprint vs IP+UA

Step 1 — Define what 'duplicate' means for this offer. Same user twice? Same device? The advertiser's definition decides yours.
Step 2 — Match method to traffic.
☐ Cookie-based → cleanest, but fails on in-app browsers, incognito, iOS ITP. Use for desktop web.
☐ IP + User-Agent hash → survives cookie loss, but collides on shared NAT (offices, mobile carriers). Use for mobile pop.
☐ Full fingerprint (canvas, fonts, screen) → most durable, heaviest, and legally sensitive in EU. Use only where consented.
Step 3 — Set the window. 24h is standard; match it to the advertiser's own attribution window or you'll fight over duplicates.
Step 4 — Log the method per click so disputes are auditable.

Tradeoff: stronger dedup cuts fraud but raises false positives on shared IPs.

Re-validate dedup collision rate monthly against a known-clean segment.