Glossary
Click ID
A unique value an ad platform adds to the landing page URL on each click, such as Google's gclid or Meta's fbclid, so a later conversion can be matched to it.
Also called: click identifier, ad click ID
When someone clicks an ad, the platform adds a parameter to the destination URL. Google uses gclid, Meta
uses fbclid, and other networks use their own names. The value is the click ID: a random token that the
platform can look up later.
The click ID must travel from the ad click to your site, into your database, and back to the platform with the conversion. When it makes the whole trip, the platform matches the conversion to one specific click. This is deterministic attribution: a match on a stored value, with no estimate of who the visitor was.
Where it breaks. These steps lose the click ID most often:
- a redirect that drops query parameters
- a form with no hidden field to carry it
- a checkout on another domain that does not receive it
- a visitor who returns days later through organic search, on a visit that has no click ID
Why it lasts. The click ID travels in the URL, not in browser storage. Cookie limits do not shorten its life, so it often survives where cookie-based methods fail.
Other click IDs. Tracking and partner platforms create their own IDs, such as impact.com’s im_ref or
Everflow’s transaction ID. These identify a visit in the tracker, and an ad platform cannot match on them.
Two kinds of click ID explains the difference.
How to test it. Click your own ad and complete a conversion. Then check that the click ID is present at each step: the landing page URL, the form or checkout, your database, and the conversion you send back to the platform.
Do not confuse with
Close enough to get mixed up, different enough that the mix-up costs something.
- Cookie window How long a tracking cookie stays valid after a browser stores it. When the cookie expires, a returning visitor can no longer be linked to the earlier click.
- Identity resolution Linking separate records, such as a click, a session, an order and an email, to one person. Errors in this step carry into every report built on top of it.
- UTM parameters Tags added to a URL, such as utm_source and utm_campaign, that tell your analytics where a visit came from. Ad platforms do not use them to match conversions.