What is gclid?

Who adds it

Google Ads adds it when auto-tagging is on, which Google switches on automatically when an advertiser creates a conversion action. It's appended to the landing page URL of every ad click.

What it means

The visit came from a Google ad. Google Analytics reads the gclid and reports the visit as google / cpc even without UTM tags, and the Google tag stores it in a first-party cookie for conversion tracking.

What to do with it

Make sure redirects pass it through to the final page, or conversions go unrecorded. Google's canonical docs use a ?gclid= URL as the example of a duplicate that should point at the clean URL.

How Vireo shows it

Vireo doesn't store click IDs, in the free plugin or in Pro.

In the free plugin, Vireo drops the query string from page addresses, keeping only a few WordPress ones such as p and page_id, so a tagged URL counts as the same page as the untagged one. The visit is counted under the referrer it arrived with.

See Referrers and sources in the docs.

Sources

For example, if someone clicks on your ad for www.example.com , the final URL will look like www.example.com/?gclid=123xyz.

About auto-tagging - Google Ads Help

unlinked Google Ads campaigns will still appear in reports by default with a source/medium of google/cpc or using available UTM values.

Campaigns and traffic sources - Analytics Help

You might prefer people to reach your green dress product page through https://www.example.com/dresses/green/green-dress.html rather than https://example.com/dresses/cocktail?gclid=ABCD.

How to Specify a Canonical with rel="canonical" and Other Methods - Google Search Central