Meta Click ID (fbc) Implementation & Verification Guide

This guide ensures the Facebook Click ID is captured from the URL, stored in a 1st-party cookie, and passed to both the Meta Pixel and Conversions API (CAPI) using Google Tag Manager.

Part 1: Implementation Steps

1. Capture the ID (Web Container)

• Variable: Create a URL variable named {{URL - fbclid}} with Query Key fbclid.

• Cookie Setter Tag: Create a Custom HTML Tag with the script below. Set the trigger to All Pages (Container Loaded).

<script>
  (function() {
    var urlParams = new URLSearchParams(window.location.search);
    var fbclid = urlParams.get('fbclid');
    if (fbclid) {
      var timestamp = new Date().getTime();
      var fbcValue = 'fb.1.' + timestamp + '.' + fbclid;
      var date = new Date();
      date.setTime(date.getTime() + (90 * 24 * 60 * 60 * 1000)); // 90 Days
      document.cookie = "_fbc=" + fbcValue + "; expires=" + date.toUTCString() + "; path=/; domain=." + location.hostname.replace(/^www\./, "");
    }
  })();
</script>

2. Configure the Data Bridge

• 1st-Party Cookie Variable: Create {{Cookie - fbc}} for cookie name _fbc. In settings, check “Convert undefined to…” and leave it blank.

• Google Tag (GA4): Set the trigger to All Pages (Container Loaded). In Configuration Parameters, add:

  • Field: x-fb-ck-fbc | Value: {{Cookie - fbc}}

3. Map to Server (Server Container)

• Event Data Variable: Create {{ED - x-fb-ck-fbc}} with Key Path x-fb-ck-fbc.

• Meta CAPI Tag: Map the Click ID field to {{ED - x-fb-ck-fbc}}.

Part 2: How to Check if it Works

1. Browser Level (The Cookie)

• Visit your site with ?fbclid=TEST_ID in the URL.

• Open Inspect > Application > Cookies.

• Verify _fbc exists with the format: fb.1.[timestamp].TEST_ID.

2. GTM Level (The Data Flow)

• Web Preview: Click the Google Tag. Under Configuration Parameters, confirm x-fb-ck-fbc has a value (not “undefined”).

• Server Preview: Click the incoming /collect request. In the Event Data tab, confirm x-fb-ck-fbc is present with the correct string.

• CAPI Tag: Under the Tags tab in Server Preview, click the Meta CAPI tag. Check the outgoing payload for the “fbc” or “Click ID” field.

3. Meta Level (The Processing)

• In Meta Events Manager, go to Test Events.

• Navigate your site. Confirm “Server” events appear.

• Click an event and verify the fbc parameter is listed under event details.