Definition
GCLID stands for Google Click Identifier. When auto-tagging is enabled in a Google Ads account, every ad click arrives at your site with a gclid=... query parameter in the URL. The value is an opaque string that uniquely identifies that click inside Google's systems. Stored and passed back to Google later via the offline conversions API, the GCLID tells Google which ad click produced a sale - even if the purchase happened weeks later on a phone call.
Without GCLID capture, Google Ads can only attribute conversions that happen on the website itself during the same session. With GCLID capture, you can upload phone sales, contract signatures, or trial-to-paid upgrades and have Google properly credit the originating click in your ROAS reporting. This is the backbone of every serious B2B Google Ads program.
How SheetLinkWP relates to GCLID
SheetLink Forms reads gclid, fbclid, and msclkid from the page URL at form submission time and writes them to dedicated columns in your Google Sheet. From there, you can upload offline conversions to Google Ads, Meta, or Microsoft Advertising using their standard offline-conversion CSV workflows, closing the loop between ad spend and downstream revenue. See the UTM tracking use case for a full walkthrough.