Set up SourceTag with Klaviyo

Klaviyo captures UTM parameters from URLs automatically. But SourceTag adds more: channel categorisation, smart fields, click IDs, visit counts, and first click / last click attribution. Here’s how to get that data into Klaviyo.

What you need

• SourceTag installed on your site
• A Klaviyo account

Option 1: Use a third-party form (recommended)

If your site uses a form builder like Gravity Forms, WPForms, HubSpot Forms, or Typeform, you can connect it to Klaviyo via Zapier or Make. SourceTag populates hidden fields in these forms, and the data flows through to Klaviyo as custom properties.

1. Set up SourceTag hidden fields on your form (see your form builder setup guide)
2. Connect the form to Klaviyo via Zapier or Make
3. In the Zap/scenario, map each SourceTag field to a Klaviyo profile property

Core fields (map these)

SourceTag field	Klaviyo property name	Description
st_fc_channel	st_fc_channel	First click channel
st_fc_detail_1	st_fc_detail_1	First click smart field 1
st_fc_detail_2	st_fc_detail_2	First click smart field 2
st_fc_detail_3	st_fc_detail_3	First click smart field 3
st_fc_detail_4	st_fc_detail_4	First click smart field 4
st_lc_channel	st_lc_channel	Last click channel
st_lc_detail_1	st_lc_detail_1	Last click smart field 1
st_lc_detail_2	st_lc_detail_2	Last click smart field 2
st_lc_detail_3	st_lc_detail_3	Last click smart field 3
st_lc_detail_4	st_lc_detail_4	Last click smart field 4
st_fc_landing_page	st_fc_landing_page	First click landing page
st_lc_landing_page	st_lc_landing_page	Last click landing page

Optional extended fields

If you’ve enabled extended field groups in your SourceTag dashboard, also map:

SourceTag field	Klaviyo property name	Description
st_fc_click_id	st_fc_click_id	First click ID (gclid, fbclid, etc.)
st_lc_click_id	st_lc_click_id	Last click ID
st_visits	st_visits	Visit count
st_days_to_convert	st_days_to_convert	Days to conversion
st_device	st_device	Device type

See Captured Fields for the full list of available fields.

Option 2: Use the SourceTag JavaScript API

If you use Klaviyo’s own signup forms (popups, embedded forms), SourceTag can’t populate hidden fields in them directly because Klaviyo forms don’t support dynamic hidden field values.

Instead, use SourceTag’s JavaScript API to read the attribution data and pass it to Klaviyo via their JavaScript API:

// After Klaviyo form submission
var st = window.__sourcetag;
if (st) {
  var fc = st.getFC();
  var lc = st.getLC();
  var meta = st.getMeta();
  if (fc && window._learnq) {
    window._learnq.push(['identify', {
      'st_fc_channel': fc.channel,
      'st_fc_detail_1': fc.d1,
      'st_fc_detail_2': fc.d2,
      'st_fc_detail_3': fc.d3,
      'st_fc_detail_4': fc.d4,
      'st_fc_landing_page': fc.lp,
      'st_lc_channel': lc ? lc.channel : fc.channel,
      'st_lc_detail_1': lc ? lc.d1 : fc.d1,
      'st_lc_detail_2': lc ? lc.d2 : fc.d2,
      'st_lc_detail_3': lc ? lc.d3 : fc.d3,
      'st_lc_detail_4': lc ? lc.d4 : fc.d4,
      'st_lc_landing_page': lc ? lc.lp : fc.lp,
      'st_visits': meta ? meta.visits : null,
      'st_days_to_convert': meta ? meta.dtc : null,
      'st_device': meta ? meta.device : null
    }]);
  }
}

This updates the Klaviyo profile with attribution data after the form is submitted.

Option 3: Klaviyo’s built-in UTM tracking

Klaviyo automatically captures UTM parameters from the URL when someone submits a Klaviyo form. This gives you utm_source, utm_medium, and utm_campaign on the profile. However, it does not give you channel categorisation, smart fields, click IDs, or first click / last click attribution. If basic UTM tracking is enough, you may not need SourceTag for Klaviyo forms specifically.

Test

1. Visit your site with UTM parameters: ?utm_source=test&utm_medium=cpc&utm_campaign=klaviyo-test
2. Submit a form
3. In Klaviyo, find the profile and check the custom properties

Tips

• Option 1 (third-party form via Zapier) is the most reliable approach
• Klaviyo property names are case-sensitive
• You can segment subscribers by st_fc_channel to see which channels drive signups