Webflow
Webflow's native form fields don't expose a default value, so the clean install is an Embed element with prewritten hidden inputs — the same pattern as the Custom HTML guide, dropped inside your Form Block.
Add the tag to your site
In Project Settings → Custom Code, paste the loader into Head Code, then publish.
<script src="https://attr.boggsmtk.com/v1/tag.js?k=YOUR_LICENSE_KEY"></script>
Swap YOUR_LICENSE_KEYfor the client's key from the dashboard.
Put it in the <head> directly, not in Google Tag Manager. When GTM is blocked — an ad blocker, a privacy browser, a consent banner the visitor never accepts — nothing inside the container fires, and a tag that lives in GTM never loads. That lead arrives with empty attribution fields. Loaded straight from the <head>, the tag runs whether or not GTM does. A GTM Custom HTML tag on all pages still works if the <head> is genuinely off-limits, but treat it as the fallback, and expect to lose the leads whose browser blocks the container.
Add an Embed Code to your form
In the Designer, drop an Embed element inside your Form Block (Add panel → Embed).
Paste your hidden inputs into it following the Custom HTML install guide — it has the complete copy-paste field set. Webflow submits every input inside the Form Block, so each one becomes a field on the Submissions page and a row in your lead notification emails.
Publish
Publish the site. The tag populates the fields on page load and again at submit, so attribution rides along with the lead.
value (each cell has a copy button); naming details are in the Custom HTML guide.