How to Prepare a GCLID Offline Conversion Upload for Google Ads

If your Google Ads account already uses the legacy offline conversion file workflow, the CSV needs to connect each offline event back to the ad click that created the lead. That connection is the Google Click ID (GCLID).

Keep the GCLID in your CRM

The GCLID must survive the full lead journey: landing page, form submission, CRM record, qualification, and sale. If it disappears before the offline event happens, a legacy GCLID-only upload cannot match that event back to the click.

Map the required columns

For the legacy mode, map Google Click ID, Conversion Name, and Conversion Time. The conversion name must match the action configured in Google Ads. Add Conversion Value, Conversion Currency, and Order ID when your source contains them.

Use a conversion timestamp with an explicit timezone so the event is unambiguous. The mapper deliberately leaves timestamps unchanged rather than guessing a timezone.

Remember that this path is legacy

Google recommends Enhanced Conversions for Leads for new offline lead measurement. Enhanced leads can supplement click identifiers with first-party user data and are the direction Google is moving new integrations. Use the GCLID-only mode when you are maintaining an existing file-based offline conversion action, not as a default architecture for a new setup.

The mapper processes one CSV locally up to 200 MB and downloads a new mapped file. Review Google's current upload screen before importing because account-level requirements can change independently of your source CSV.

Prepare a legacy GCLID conversion CSV

See the transformation

Awkward source headers become import-ready columns.

Rename the columns you need while keeping every value under the correct header.

cust_idcustomer_id

given_namefirst_name

mailemail

✓ Values stay with the right column