Click ID

When someone clicks an ad, the platform adds a parameter to the destination URL — Google uses gclid, Meta uses fbclid, and every other network has its own name for the same idea. That string is the click ID: an opaque token that means nothing on its own but that the platform can look up later.

Its whole job is to survive. If it makes it from the ad click into your site, then into your database, and finally back to the platform alongside the conversion, you get deterministic attribution — not a guess about who this person probably is, but a direct match on a specific click.

Where it breaks. The click ID is fragile in exactly the places nobody checks. A redirect that strips query parameters loses it. A form that does not carry it into a hidden field loses it. A checkout on a different domain loses it unless you deliberately pass it across. A user who bounces and returns three days later through organic search arrives without one.

Why it matters more every year. As browsers restrict cookies and cross-site tracking, the click ID has become the most durable link between an ad and a sale. It travels in a URL, not in browser storage, which is why it survives conditions that break other methods.

The practical test is unglamorous: click your own ad, complete a conversion, and check whether the click ID is present at every step. Most tracking gaps are found in about ten minutes this way.