1. Create a custom lead field called UTM source (logical name: utmsource).
   
2. Make a new form for leads and add the UTM source field.
   
3. Set that field to hidden in the form settings.
   
4. Open the HTML editor and paste in the provided script.
   
5. Update the script’s field ID to match your form’s field.

Reuse this example to enrich your leads with more UTM parameters, like utm_campaign, utm_medium, utm_term, and utm_content.

<script>
document.addEventListener("d365mkt-afterformload", updateUTMSourceField());

function updateUTMSourceField() {

const formField = document.getElementById("utmsource-1679335998029"); // The field ID is unique in each form, make sure you replace it with the correct value.        

const urlParams = new URLSearchParams(window.location.search);

const utmSource = urlParams.get('utm_source');

formField.value = utmSource;

console.log(utmSource); // for debug only, can be removed

}
</script>