19th of 20 Questions.
What APIs and features are not available inside a Web Worker? (e.g., DOM, window, document)
Workers cannot access DOM, window, document, parent, alert, localStorage, or most UI-related APIs. They can use fetch, XMLHttpRequest, IndexedDB, WebSocket, setTimeout, navigator, location (read-only), crypto, and Worker itself.
Workers run in a separate global scope (DedicatedWorkerGlobalScope). They have no access to UI APIs, preventing race conditions with rendering. Available APIs include network, storage, and timers, making them suitable for background processing.