URL Toolkit is a lightweight JavaScript library that implements RFC 1808 to resolve a relative URL against a base URL, producing an absolute URL. It also provides utilities for parsing URLs, normalizing paths, and rebuilding URLs from components, and can be used both in Node / npm projects and directly in browsers. It’s aimed at developers who need precise, spec‑compliant URL handling (e.g., media streaming libraries like HLS.js) rather than the broader behavior of the native `URL()` constructor.