Disclosure

Transparency about links, funding, scope, and your data — per FTC guidance.

urldiffer is free. Some outbound links — for example to security testing tools, hardened URL libraries, or learning resources — may be affiliate links: if you sign up through them we may earn a commission at no extra cost to you. Paid links are marked rel="sponsored nofollow".

We only link to things we'd actually use, and a commission never changes what the tool reports. Every result follows the published methodology.

Scope & not a safety guarantee. urldiffer is an educational, deterministic parsing tool. It computes two exact parsers (WHATWG and RFC 3986) and explicitly-defined naive checks for the input you give it; it does not run other languages’ libraries, does not fetch the URL, and a green result is not a proof that your application is safe. For production decisions, test against the real libraries in your stack and use a hardened, allowlist-by-resolved-IP approach.

Your privacy: this is a static, client-side tool. The URL you paste is processed in your browser and is never uploaded or fetched — there is no backend and nothing is logged.