Examples

Worked examples — each page is one real problem, the awkward way to solve it without URLPattern, and the URLPattern-shaped replacement. Every snippet has been verified against the test suite.

Web routing

• Route a multi-tenant API by subdomain
• Add subdomain routing to aiohttp
• Add subdomain routing to FastAPI
• Validate inbound webhooks by URL shape

Security

• Avoid regex hostname-allowlist credential leaks

AI / model serving

• Match the KServe /v2/models inference path
• Pick an LLM backend by model name
• Replace MCP resource URI templates
• Translate google.api.http to URLPattern

Text + data pipelines

• Classify GitHub URLs in markdown
• Extract YouTube video IDs from any URL form
• Match Slack callback IDs with structured data

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Every example follows the same shape:

1. The problem — what someone is actually trying to do, with a real public reference (issue link, blog post, framework doc).
2. The awkward way — typical Python today: urlparse + if host == … ladders, hand-rolled regex, or framework-specific config gymnastics.
3. With URLPattern — one declarative pattern, structured match result.
4. What you get for free — which URLPattern feature carried the weight (cross-component matching, optional segments, named groups with regex, compare_component(), custom-scheme support, …).