GA4 + GTM Full Funnel Implementation

Context

Tracking pageviews, and nothing else.

A SaaS B2B company had GA4 installed on their marketing site but was effectively flying blind. Pageviews were being tracked. Everything else — form submissions, demo requests, pricing page visits, CTA clicks — was invisible. Marketing decisions were being made without data.

Problem

Leads arriving with no source attribution.

GA4 out of the box tracks pageviews. It tracks nothing else unless you tell it to. The team had no visibility into which traffic sources were generating demo requests, which landing pages were converting, or where users were dropping off in the funnel. HubSpot was active but disconnected from web analytics — leads were arriving in the CRM with no source attribution.

Diagnosis

A GTM container installed, but empty.

• GA4 property active but no custom events configured
• GTM container installed but empty — no tags, no triggers, no variables
• HubSpot form present on multiple pages — no tracking on submission
• UTM parameters not being captured or passed to CRM
• No visibility into pricing page engagement or CTA click behavior

Constraints

What the implementation had to work within.

• No direct access to site codebase — all implementation via GTM
• HubSpot integration required coordination with the client's CRM setup
• Events had to be validated in production — no staging environment

Implementation

Six events, validated before handoff.

GTM container built from scratch — data layer configured, variables defined for consistent event naming across the funnel.

6 conversion events implemented and validated:

• Demo request form submission
• Pricing page visit
• Primary CTA click (above fold)
• Secondary CTA click (footer)
• HubSpot form submission
• Contact page engagement

UTM attribution configured — source, medium, campaign, and content parameters captured on landing and passed through to HubSpot via hidden form fields.

HubSpot integration validated — leads arriving in CRM with full UTM attribution visible on contact record.

All events validated via GA4 DebugView in real time before handoff.

Tradeoffs

DOM triggers, documented as a maintenance cost.

Implementing via GTM without codebase access means relying on CSS selectors and DOM triggers for event detection. These require maintenance if the site's HTML structure changes. This tradeoff was documented and communicated to the client at handoff.

Stack

Before / After

From pageviews-only to full funnel.

Outcome

Full funnel visibility, for the first time.

Marketing team gained full visibility into funnel performance for the first time. Demo requests trackable by source, medium, and campaign. HubSpot leads arrive with complete attribution. Foundation in place for A/B testing and conversion optimization.

Lessons

Installing the script is 5% of the work.

GA4 is not a plug-and-play analytics solution. Installing the script is 5% of the work. The other 95% is defining what matters to the business, building the event taxonomy, and validating that what you're measuring is actually what you think you're measuring.