1. JavaScript modules via script tag

    Loading JavaScript module scripts (aka ES6 modules) using `<script type="module">` Includes support for the `nomodule` attribute.

  2. JavaScript modules: dynamic import()

    Loading JavaScript modules dynamically using the import() syntax

  3. CSS Font Loading

    This CSS module defines a scripting interface to font faces in CSS, allowing font faces to be easily created and loaded from script. It also provides methods to track the loading status of an individual font, or of all the fonts on an entire page.

  4. IntersectionObserver

    API that can be used to understand the visibility and position of DOM elements relative to a containing element or to the top-level viewport. The position is delivered asynchronously and is useful for understanding the visibility of elements and implementing pre-loading and deferred loading of DOM content.

  5. Resource Hints: Lazyload

    Gives a hint to the browser to lower the loading priority of a resource. Please note that this is a legacy attribute, see the [`loading`](/loading-lazy-attr) attribute for the new standardized API.

  6. Lazy loading via attribute for images & iframes

    The `loading` attribute on images & iframes gives authors control over when the browser should start loading the resource.

  7. zstd (Zstandard) content-encoding

    Data compression method providing faster page loading while using less CPU power on the server.

  8. applicationcache api: `downloading` event

  9. fontfaceset api: `loadingdone` event

  10. fontfaceset api: `loadingerror` event

  11. fontfaceset api: `loading` event

  12. htmliframeelement api: loading

  13. htmlimageelement api: loading

  14. performancetiming api: domloading

  15. html element: iframe: loading

  16. html element: img: loading

  17. headers http header: supports-loading-mode

  18. headers http header: supports-loading-mode: `credentialed-prerender` directive

  19. headers http header: supports-loading-mode: `fenced-frames` directive