## TL;DR

The Navigator API (`window.navigator` / `navigator`) provides information about the browser and device. Key properties include `userAgent`, `language`, `onLine`, `platform`, `hardwareConcurrency`, and access to various sub-APIs (`geolocation`, `clipboard`, `mediaDevices`).

## Core Explanation

`navigator.userAgent` (becoming less reliable due to freezing), `navigator.language` (user's preferred language), `navigator.onLine` (connectivity status), `navigator.hardwareConcurrency` (logical CPU cores), `navigator.cookieEnabled`, `navigator.platform`. Sub-APIs: `navigator.geolocation`, `navigator.clipboard`, `navigator.mediaDevices`, `navigator.serviceWorker`.

## Further Reading

- [HTML Standard — Navigator](https://html.spec.whatwg.org/multipage/system-state.html#the-navigator-object)