Canonicalize a URL: WHATWG parsing already lowercases the host, resolves dot-segments and drops default ports; on top of that, query parameters are sorted by default and you can optionally drop the fragment or a trailing slash. Returns the normalized URL and whether it changed.

Parse an absolute URL into its WHATWG components: protocol/scheme, credentials, host/hostname/port, origin, pathname (plus path segments), search (plus a decoded query object) and hash. A string that is not a valid absolute URL is rejected as a clean 400.

Two directions over query strings. action='parse' decodes a query string (with or without a leading '?') into an object, collapsing repeated keys into arrays. action='build' encodes a params object into a query string, expanding array values into repeated keys; set sort=true to order keys alphabetically.

Resolve a relative or absolute reference against a base URL, following RFC 3986 reference resolution (e.g. base 'https://a.com/x/y' + ref '../z' → 'https://a.com/z'). The base must itself be a valid absolute URL, else a clean 400.