HTML5 introduced several APIs that allow web developers to create more powerful and interactive web applications. Here are the most used HTML5 APIs

Geolocation API
Enables web applications to access the user's geographical location.

Local Storage
localStorage keeps data stored persistently across browser sessions, maintaining it indefinitely unless intentionally cleared by the user or the application.

Canvas API
•  Allows for dynamic, scriptable rendering of 2D shapes and bitmap images.  
•  It's commonly used for creating games, data visualizations, and other graphical applications.

Web Audio API
Manipulates audio in web apps

WebSockets
Enables real-time communication such as chat applications and online gaming

WebRTC
Facilitates browser-based real-time peer-to-peer communication between browsers

Web Workers
Runs scripts in background threads.  
This allows for concurrent processing and helps prevent UI freezes.