How the gclid works
Google defines it simply: "Google Click ID (GCLID) is a URL parameter passed with ad clicks." It carries details about the click, such as the campaign, so Google can tie what happens next back to the ad.
You turn it on with the auto-tagging setting in Google Ads. Google's example of what the landing page URL then looks like is www.example.com/?gclid=123xyz.
Google says the gclid is required for Google Ads website conversion tracking. It also links Google Ads data with Google Analytics, and it is used for offline conversion tracking, where you send Google the leads that turned into jobs.
On iPhones, some clicks use other parameters instead. See what gbraid and wbraid are.
How redirects lose the gclid
Google's auto-tagging page says to make sure the GCLID is passed to the final landing page in order to track conversions. Redirects are where that breaks.
Google's Analytics help says that if your website has redirects, you need to keep the gclid parameter in the redirect. A redirect can also have more than one step, and the gclid can drop at any of them. Common cases on lead pages:
- The ad points at an old URL that now redirects to a new page.
- A rule that forces https, www, or a trailing slash and does not carry the query string over.
- A separate mobile page that the server sends phones to.
Google's fix order: set the ad's destination to the final URL so no redirect happens. If a server rule causes the redirect, change it. If you cannot stop the redirect, set the server to pass query parameters, including the gclid, to the final URL.
How to check yours
Google's test: open Chrome DevTools and the Network tab, then load your final URL with a test parameter like ?gclid=TeSter-123 on the end. Look for 301 or 302 responses, which mean a redirect, and check that the gclid is still on the URL where you land.
For a quicker check, use the gclid checker. Then run a free ClickMend scan on the same final URL. It checks whether a Google Ads conversion tag is on the page, whether it actually loaded, and whether the conversion linker is turned off. The conversion linker is what stores the click details so the conversion can find them later.
Frequently asked questions
How do I turn the gclid on?
Turn on auto-tagging in Google Ads. Google says auto-tagging adds the GCLID parameter to the URL people reach when they click your ad.
My page shows an error when gclid is in the URL. What now?
Google says some sites do not allow arbitrary URL parameters and serve an error page when auto-tagging is on. Have your web developer allow arbitrary URL parameters.
Does every iPhone click carry a gclid?
Not always. Google's iOS 14 update page says it no longer sends the GCLID for iOS 14 traffic from ads on a handful of Google apps, and uses other parameters instead.