Hi @Geert,
All Builder content is fully server-side serializable to HTML. This means we can pre-render all content to optimized HTML, and remove all blocking scripts or styles. This way we can deliver content as very lightweight HTML and lazily load any additional JS, CSS, etc. for interactive elements which are hydrated after the initial load.
We do this in a modern style similar to Gatsby, Next.js, and Nuxt - and can work within any of those frameworks (and others!) natively as well.
If you wish to add fetchpriority=“high” attribute to a specific image you can use the below JS code
let image = document.querySelector('.class-name-of-image');
image.setAttribute('fetchpriority' , 'high');
You can also check out our Qwik API, which is our new, ultra-performance optimized alternative to our HTML API. It uses Qwik to prerender your content to optimized HTML that requires 0 JS to run (even if it has dynamic content!)