GCLID (Google Click Identifier)
GCLID is the unique tracking parameter Google Ads appends to ad click URLs (`?gclid=XYZ`) to identify each individual click. Capturing the GCLID in a hidden form field, persisting it through the lead-to-sale lifecycle in a CRM, and uploading it back to Google as an offline conversion is the most accurate way to tie a closed deal to the originating ad click.
In depth
Round-trip flow: ad click sets GCLID → form capture stores GCLID in CRM lead → sales-stage transition (e.g., 'qualified') triggers conversion upload via Google Ads API or Google Sheets import → Smart Bidding optimizes against the downstream event, not the form-fill.
GCLID expires 90 days after click; offline conversion uploads against expired GCLIDs are silently dropped. Time-sensitive for accounts with long sales cycles.
Auto-tagging must be enabled in Google Ads account settings for GCLID to be appended. Disabled by default in some legacy accounts.
GCLID-based imports are more accurate than Enhanced Conversions (PII-hashed) but require explicit CRM field plumbing. Most accounts run both for maximum match coverage.
Common misconception
GCLID is not the same as a UTM parameter. UTMs are advertiser-defined and human-readable; GCLID is Google-generated and required for offline-conversion attribution. A CRM that captures UTMs but not GCLID cannot perform Smart Bidding offline-conversion uploads.
Source: Google Ads — About auto-tagging and GCLID
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