Tracking and measurement
Click ID (gclid, fbclid, ttclid)
A unique identifier added to a landing page URL when someone clicks an ad (Google, Meta, TikTok). Capturing it is how a later purchase can be tied back to the click.
A click ID is a unique identifier that an ad platform appends to the landing page URL when someone clicks an ad: gclid for Google, fbclid for Meta, ttclid for TikTok. If the store captures and stores it with the visitor and later with the order, a purchase can be sent back to the platform tied to the exact click that led to it.
Click IDs are what make server-side conversion reporting precise. A server event that carries the stored click ID is matched directly, without relying on cookies that may have expired or been blocked. Losing the click ID between landing and checkout, for example through a redirect, a domain change or a consent tool that strips parameters, is a common and invisible source of missing conversions.
When an assistant compares ad platform conversions with store orders, a large gap for one channel often traces back to click ID capture on that channel. The assistant can surface the gap; confirming the cause means checking the landing page URLs, the storage of the parameter and what the server sends.