gclid

The gclid (Google Click Identifier) is a unique ID that Google Ads automatically appends to the landing page URL whenever someone clicks an ad – for example ?gclid=EAIaIQobChMI…. Using this ID, Google can later trace which click led to which conversion: keyword, ad, campaign and time.

How the gclid works

1. A user clicks your Google ad.
2. Google adds the gclid to the URL (auto-tagging must be enabled).
3. The Google Ads tag or another tracking tool stores the gclid on your website.
4. When a conversion happens, the gclid is reported to Google together with the event – via a browser tag or server side.

Unlike UTM parameters, the gclid isn't human-readable. Only Google can match it to a click.

Example

A real estate agent runs Google Ads campaigns for seller leads. A lead requests a valuation, and six weeks later the listing agreement is signed. If the gclid was stored with the lead, the deal can be reported back to Google with a value of, say, $9,000 in commission. Google then knows which keyword brought in real business, not just inquiries.

gclid for lead generation

For offline conversions, the gclid is the key: only if it ends up with the lead in your CRM can a later deal be tied back to the original click. Google only accepts these imported conversions for a limited time after the click – the faster you report the deal, the better.

LeadMetrics captures the gclid automatically on the visit, stores it in the session and links it to the lead (lead tracking). Leads, deals and payments are then sent to Google Ads with the gclid via the Conversion API.

Common mistakes

• Auto-tagging off: No auto-tagging, no gclid.
• Redirects that drop parameters: Redirects or cookie banner reloads cut off the gclid.
• Not passing the gclid to the CRM: The deal can't be attributed to a click later.
• Mixing it up with the fbclid: The fbclid is Meta's counterpart and only works there.