In this live project, I show you the complete Klaviyo Facebook CAPI server-side setup with GTM — both browser + server working together. I start from the browser side first, where I push the Klaviyo form submission data into the dataLayer using a Custom HTML/JavaScript approach. The main goal is to capture the real lead form details (form ID, form title, email, and full name) and then map everything properly inside Google Tag Manager with dataLayer variables. After that, I build the browser-side Facebook Pixel custom event (because this is not a standard event). I pass all the event parameters as object properties, and I also handle the “full name” issue by splitting it into first name and last name using custom JavaScript — this helps to increase event match quality. One important thing I follow is hashing user data (like email and user info), because if you don’t follow hashing, you will see problems later inside Facebook Events Manager diagnostics. Finally, I configure the GTM Server container for Facebook Conversion API and send key signals like fbp/fbc cookies, event_id, event_time, and external_id to improve EMQ and attribution. Then I test the browser + server event match, verify everything in Events Manager, and confirm the events are receiving data perfectly (including deduplication using event_id).