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Overview

The 30-second story:

  • yarlpattern is the Python implementation of the WHATWG URLPattern Standard.
  • URLPattern matches every URL component (protocol, hostname, port, path, search, hash) declaratively, with named groups per component.
  • It's the same standard Chromium, Safari, Firefox, Deno, Bun, Node.js, and Cloudflare Workers implement — yarlpattern brings it to Python with 100% conformance to the upstream WPT corpus (469 / 469 cases across 5 suites).

What's in this section

  • What is URLPattern? — origin story (URLPattern began as a service-worker scoping mechanism, not a developer routing toolkit), why the syntax mirrors path-to-regexp rather than the OpenAPI {name} style, what component-wise matching means in practice, and the canonicalize-then-match semantics that surprise everyone porting from substring matching. Ends with three recommended intros to read before any Python.
  • Ecosystem adoption — chronological timeline from 2020 incubation to Baseline Newly Available status in September 2025, plus current snapshot tables for browsers, server runtimes, and frameworks.

Want to skip to the code?

  • Examples — 11 worked examples ("classify GitHub URLs in markdown", "route a multi-tenant API by subdomain", "match the KServe inference path", …) each verified against the test suite.
  • API reference — auto-extracted from the source's docstrings.