I’ve been trying to get this working using all sorts of guides and bits of code, but no success yet.

I’m using Acerill forms, which has a hidden field, that needs Javascript to pull in the data:
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I’ve tried everything on the first couple pages of Google. Even the Measure School https://measureschool.com/capture-utm-parameters-in-form-fields/ guide, which still didn’t work as I can’t find the element class name for the hidden field uisng inspect.

This is the page with the test form: https://neonfilter.com/pages/new-site-test-page if anybody can help me I’d be incredibly thankful!!

Cheers
Kerri