FIELD GUIDE · HUBSPOT & GOOGLE ADS

Why HubSpot Receives UTMs but Drops Google Ads GCLID

A common paid search bug: HubSpot contact records show utm_source=google, yet the Google Click ID (gclid) field is blank.

1. Where GCLID Gets Dropped

Canonical 301 Trailing-Slash Redirects: Server rules rewrite /demo to /demo/, keeping whitelisted utm_* parameters while stripping gclid.
Cookiebot / OneTrust Timing Race: HubSpot checks for _gcl_aw before Google Conversion Linker runs after consent acceptance.
Missing Hidden Field: The form lacks an explicit <input type="hidden" name="gclid"> inside cross-origin embeds.

2. Raw Protocol HAR Inspection Example

GET /demo?gclid=zst_test_84b12&utm_source=google&utm_medium=cpc HTTP/2
Host: example.com

HTTP/2 301 Moved Permanently
Location: https://example.com/demo/?utm_source=google&utm_medium=cpc
# 'gclid' was stripped on the 301 redirect

3. How to Fix It

# Nginx redirect rule preserving all query parameters including gclid
# In a port 80 HTTP-only server block; never in the HTTPS block.
return 301 https://$host$request_uri;

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