GCLID

What Is GCLID?

GCLID stands for Google Click Identifier and is a unique parameter that Google automatically adds to URLs in Google Ads. Every time a user clicks on a Google Ads ad, a GCLID parameter is appended to the landing page URL (e.g., www.example.com/?gclid=ABC123…). This GCLID allows Google and website owners to connect the click on an ad with a subsequent action on the website (conversion). For Google Ads attribution and conversion tracking, GCLID is central — without GCLID, Google cannot know which conversions came from which ad clicks.

The technical process is automatic: Google Ads generates a unique GCLID for each click, and when the user reaches the landing page, the GCLID is transmitted in the URL. When a conversion tracking pixel (e.g., Google Ads Conversion Tracking or Google Tag Manager) fires on the conversion page, it captures the GCLID and sends it along with the conversion information to Google. Google then connects the data and shows the advertiser that this click led to a conversion. The Enhanced Conversions feature also uses GCLID to connect offline conversions or database conversions with ad clicks.

In practice, website owners should ensure their landing pages and conversion tracking implementation correctly pass the GCLID through. If session IDs or other parameters modify the URL, the GCLID could be lost. The GCLID is valid for only one day — after that, the connection between click and conversion weakens. Analytics programs should be able to read the GCLID to connect data between Google Ads and other systems. For multi-touch attribution, it’s important to understand that GCLID only captures the last-click information — a user who first comes organically and then converts via Ads is counted as an Ads conversion.