---
id: urlcanon
version: "0.3.1"
license: unclear
license_treatment: permissive
maintenance: abandoned
---

# urlcanon — url canonicalization library for python and java

License: permissive · Maintenance: abandoned · Downloads: 147.6K/mo

## What it is and what it does

urlcanon is a URL parser and normalizer that implements the WHATWG URL standard used by web browsers. It parses URLs while preserving the original input bytes, then applies a canonicalization ruleset to normalize them into a standard form—lowercasing domains, removing default ports, resolving path segments, and collapsing redundant slashes. It also provides SSURT, an alternative serialization format designed for efficient sorting and prefix-matching of URLs.

The library is stable and has been in production use, but the project is no longer actively maintained. It offers a Python API (and a separate Java implementation). The package has no runtime dependencies, making it lightweight to install, but it is distributed only as source code, requiring compilation on install.

Use it for:

- Normalize URLs in web crawlers or archival systems to deduplicate and match equivalent URLs despite surface differences.
- Implement URL-based filtering rules by converting URLs to SSURT format for efficient prefix-matching and sorting.
- Parse and standardize URLs in data pipelines where browser-compatible normalization is required.
- Build URL deduplication logic in search indexers or link analysis tools.
- Validate and canonicalize user-supplied URLs before storage or comparison.

## Worth the install?

AI-flagged interpretation of the facts above — verify before relying.

Parses and normalizes URLs according to WHATWG browser standards, with optional SSURT serialization for sorting and prefix-matching.

No. The package is abandoned (last release 2019-07-02, no commits since 2022-05-22) and classifiers indicate support only through Python 3.7, with no verification of compatibility with later versions. The source-only distribution adds install friction. Unless you are maintaining legacy code already using urlcanon, consider a maintained alternative for new projects.

## Install

pip install urlcanon
uv add urlcanon
poetry add urlcanon

## Installing urlcanon

Before you install: High install friction: the package is distributed as a source tarball with no prebuilt wheels. Maintenance is abandoned—last release was 2019-07-02, last commit 2022-05-22, and no updates in approximately 2600 days. Classifiers list Python 2.7 through 3.7.

License in practice: Licensed under Apache License 2.0 (permissive). You may use, modify, and distribute the software freely provided you include the license notice and disclaimer.

Quickstart:

pip install urlcanon

import urlcanon
parsed_url = urlcanon.parse_url("http://EXAMPLE.com:80/foo/../bar")
urlcanon.whatwg(parsed_url)
print(parsed_url)

Source-only distribution (no wheels); requires a C compiler and build tools. Classifiers indicate Python 2.7–3.7 support; compatibility with later versions is unverified.

Verify before relying:

- Whether the package builds and runs on Python versions after 3.7.
- Whether the package has any undiscovered security issues or breaking changes since its last release in 2019.

## Package facts

- License: not declared (permissive)
- Python support: unspecified
- Install friction: high
- Maintenance: abandoned
- Downloads: 147.6K/month (top 15,000 on PyPI)
- Known vulnerabilities: none known

## Tags

url canonicalization normalization, url parser browser standard, whatwg url parsing, ssurt url serialization, url normalization library, parse url bytes preserved, url prefix matching, url-parsing, abandoned

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