A unique identifier a platform appends to an ad's landing URL when a user clicks (gclid for Google, fbclid for Meta, ttclid for TikTok, msclkid for Microsoft, li_fat_id for LinkedIn). The advertiser stores it and passes it back with the conversion, which is how offline and CRM conversions are matched to the click without cookies.
Related terms
Cite this entry:
Agency Echelon. "Click ID." Agency Echelon Reference, reviewed September 2026. https://agencyechelon.com/reference/glossary/click-id/