What is a GCLID?
The Google Click Identifier is a parameter, gclid=, that Google Ads appends to your landing page URL on every click when auto tagging is on. The Google tag reads it, stores it in a first party cookie, and uses it to link a later conversion to the exact click, keyword, ad and campaign that produced it.
Why it matters
The GCLID is how Google Ads and GA4 talk to each other. It is also how offline conversions find their way home: store the GCLID in the CRM next to the lead, and when the deal closes weeks later, upload it and the sale is credited to the click. Without it, a signed contract is invisible to the campaign that earned it.
What to check
- Auto tagging is on: in the account settings, otherwise no GCLID is ever generated.
- Redirects keep the parameter: a landing page redirect that strips the query string kills tracking silently.
- A hidden form field stores it: so every lead arrives in the CRM with its click attached.
- Enhanced Conversions for leads as backup: when the GCLID is missing, the lead's email can still close the loop.
The honest view
A redirect that drops the gclid is one of the most common and least visible tracking failures there is. Nothing breaks on screen; the campaign just stops being credited. It happens far more often than anyone admits, and it is found by testing the landing URL, not by reading a dashboard.
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