Although some browsers supported geolocation functionality prior to HTML5, it is the standardized API that brings new value.

The OpenAI WebRTC Realtime API enables real-time AI interactions directly within browsers by combining WebRTC and client-side JavaScript execution, eliminating the need for server-side processing.

The browser is a provider that offers web browsing capabilities that the JavaScript program accesses via a programming interface, the browser’s API.

From the Chromium blog: Improving the traditional browser plug-in model will make it possible for plug-ins to be just as fast, stable, and secure as the browser’s HTML and JavaScript engines.

Apple has developed a JavaScript API for its Live Photos, allowing pictures taken with the iOS feature to be shared on the web.