gclid

gclid - the Google Click Identifier - is a unique ID that Google Ads appends to your landing page URL whenever someone clicks one of your ads, provided auto-tagging is on (it is by default). The URL arrives looking like ?gclid=EAIaIQ..., and that opaque string identifies the exact click: the campaign, ad group, keyword, device, and everything else Google knows about it.

Its purpose is closing the attribution loop. If you store the gclid when a visitor converts and later report that conversion back to Google Ads alongside the same gclid, Google can attribute the outcome to the precise click that caused it. This is the basis of offline conversion imports: the ad platform learns which clicks produced real revenue, not just form fills, and its bidding optimizes toward the clicks that matter.

The catch is that a gclid is only useful if something saves it. It lives in the landing page URL and vanishes on the next navigation, so sites that want click-level attribution capture it on arrival - typically into a hidden form field or storage - and attach it to whatever the visitor eventually does.

The SheetLink Forms embed does this capture for you. sl.js reads gclid (along with wbraid, gbraid, fbclid, and msclkid, plus the five UTM parameters) from the URL, persists it in localStorage across pages, and attaches it to every submission - no hidden fields to wire up. The gclid lands as a column in your Google Sheet or Excel table next to the lead's answers, ready to export for a Google Ads offline conversion upload.

The step-by-step walkthrough is in the guide on capturing gclid in forms; the rest of the pipeline is on how it works.