URL Parser

How It Works

The WHATWG URL standard splits a URL into eight components: scheme, username, password, host, port, path, query, fragment. This tool uses JavaScript’s built-in URL class, which implements that standard — the fields below use its property names (protocol, pathname, hash, …), add the derived origin and hostname, and break the query string out into a separate parameter table.

WHATWG vs RFC 3986

It helps to know the two main specs:

• RFC 3986 — older, stricter. The IETF’s generic URI syntax.
• WHATWG URL Living Standard — modern, what browsers use. More forgiving.

Some URLs parse differently between the two specs. For example: should http://example.com get a trailing /? (WHATWG: yes, RFC 3986: not required).

This tool uses the WHATWG version — the interpretation modern browsers use.

Common sources of bugs

• URLSearchParams always returns values as strings. Reading ?count=5 means you have to do Number(searchParams.get('count')).
• Repeated parameters: for ?tag=a&tag=b, searchParams.get('tag') returns only the first value. searchParams.getAll('tag') returns both.
• Percent encoding: %20 is a space, while + means a space only in the query string. In the pathname, + is a raw character.
• IDN (internationalized domains): parsing münir.com normalizes it to xn--mnir-0ra.com (punycode).

Pathname trailing slash

Do /users and /users/ represent the same resource? In practice:

• REST APIs usually don’t distinguish them.
• Static file servers may distinguish them (/users redirects to /users/, which serves the index).
• For SEO, pick one canonical form and redirect from the other.

Privacy

The URL you paste is processed entirely in your browser.