20/06/2026
Every HubSpot form submission on your site is invisible to GA4, Meta Pixel, and Google Ads.
The fix is a Custom HTML Event Listener tag in GTM.
It listens for HubSpot's own callbacks onFormSubmit and onFormSubmitted and pushes them into the GTM dataLayer as custom events.
Once in the dataLayer, GTM can fire any tag off it GA4 lead event, Meta Pixel Lead, Google Ads conversion.
It also captures the hs-form-guid so you know exactly which form generated each lead.
No plugin. No HubSpot integration. Just clean JavaScript bridging HubSpot into GTM.