UTM parameters getting lost when someone fills in our embedded form

A lot of form tools (Typeform, Jotform, HubSpot forms) let you pass hidden field values through the embed itself. So instead of trying to read the parent page from inside the iframe, your script takes the stored UTMs and adds them to the embed URL before it loads. Way more reliable than anything clever inside the iframe.

If the form is embedded in an iframe, that's your answer. The form runs on the form tool's own domain, so it never sees the query string on your page's URL. The fix that works for us: grab the UTMs with a small script when the visitor lands, store them in a first-party cookie or localStorage, then write them into hidden fields on the form when it loads. Storing them matters because most people don't convert on the landing page, they click around first and the UTMs are gone from the URL by the time they reach the form. Also check that nothing between the ad and the page is redirecting without keeping the query string. A non-www to www redirect or a trailing slash rule can quietly strip it.