Click ID (fbclid / gclid)
Also known as: fbclid, gclid, Click Identifier
A click ID is a unique code (like fbclid or gclid) that ad platforms append to your URL so a visit can be traced back to the exact ad click.
What it actually means
When someone clicks a Meta ad, the destination URL arrives with an fbclid parameter; a Google ad appends a gclid. These click IDs are unique fingerprints for that single click, and they matter more every year as cookies erode. Captured and stored on your site, a click ID can be sent back with a conversion — through the Conversions API or an offline upload — letting the platform match the sale to the ad with far more accuracy than browser tracking alone. Sites that ignore click IDs quietly misattribute paid visitors as direct traffic; sites that capture them keep attribution intact even when the pixel is blocked.
If your analytics says most customers came from 'Direct' but you're running ads, dropped click IDs are the usual culprit — capturing them is how a plumber's ad gets credit for the job booked three days later.
Related terms
UTM parameters are tags added to a URL that tell analytics tools where a visitor came from — the source, medium, and campaign that brought them.
Attribution is the process of crediting conversions to the ads, clicks, or impressions that led to them, determining which marketing earned the result.
The Conversions API sends conversion events to Meta directly from your server, supplementing the browser pixel for more complete and reliable tracking.
The Meta Pixel is a snippet of code on your website that tracks visitor actions and sends them back to Meta for measurement and ad optimization.
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