HubSpot doesn’t support custom elements, so you will have to use our compatibility mode version of the embed code in place of the normal embed code.
Use the compatibility mode embed snippet below, and swap out the spiffy URL for the checkout you are embedding.
<div class="spiffy-checkout__container" data-url="https://example.spiffy.co/checkout/my-checkout"></div>
This compatibility mode snippet replaces part 2 of the embed code that you access within the editor.
(See normal embed code in the image below)
Learn more about compatibility mode in our developer documentation.