fqdn

Validates fully-qualified domain names against RFC 1123, so that they are acceptable to modern bowsers

fqdn Copyleft license MPL 2.0 AGING ★ 37 v1.5.1 released 2021-03-11

Install

fqdn on PyPI

pip

pip install fqdn

uv

uv add fqdn

poetry

poetry add fqdn

Package facts

License	MPL 2.0 (copyleft)
Python support	supports the current Python release (>=2.7, !=3.0, !=3.1, !=3.2, !=3.3, !=3.4, <4)
Install friction	low — pure-Python wheel
Runtime dependencies	1 — cached-property
Maintenance	aging — 1,981 days since the last release
Last repo commit	2025-03-05
First released	2017-06-06
Popularity	one of the top 1,000 most-downloaded packages on PyPI (30-day window, as of 2026-08-13)
Known vulnerabilities	none known (OSV.dev, checked 2026-08-13)

Evidence: fqdn-1.5.1-py3-none-any.whl

Keywords: fqdn, domain, hostname, RFC3686, dns

Development Status :: 5 - Production/StableEnvironment :: Web EnvironmentIntended Audience :: DevelopersIntended Audience :: System AdministratorsLicense :: OSI Approved :: Mozilla Public License 2.0 (MPL 2.0)Operating System :: OS IndependentProgramming Language :: Python :: 2.7Programming Language :: Python :: 3.5Programming Language :: Python :: 3.6Programming Language :: Python :: 3.7Programming Language :: Python :: 3.8Programming Language :: Python :: 3.9Programming Language :: Python :: Implementation :: CPythonProgramming Language :: Python :: Implementation :: PyPyTopic :: InternetTopic :: Internet :: Name Service (DNS)Topic :: System :: Systems AdministrationTopic :: Utilities

About fqdn

from the package's own PyPI description — quoted content, verbatim

.. ............................................................................. .. AMAZING REFERENCES .. ............................................................................. .. |Python Versions| image:: https://img.shields.io/pypi/pyversions/fqdn.svg :target: https://pypi.org/project/fqdn/

.. |Build Status| image:: https://github.com/ypcrts/fqdn/actions/workflows/unit-tests.yml/badge.svg :target: https://github.com/ypcrts/fqdn/actions/workflows/unit-tests.yml

.. |Coverage Status| image:: https://codecov.io/gh/ypcrts/fqdn/branch/develop/graph/badge.svg?token=cavArywW2X :target: https://codecov.io/gh/ypcrts/fqdn

.. |Latest PyPI Version| image:: https://img.shields.io/pypi/v/fqdn.svg :target: https://pypi.python.org/pypi/fqdn

.. |Downloads| image:: https://pepy.tech/badge/fqdn :target: https://pepy.tech/project/fqdn

.. |Monthly Downloads| image:: https://pepy.tech/badge/fqdn/month :target: https://pepy.tech/project/fqdn/month

.. |License Status| image:: https://app.fossa.com/api/projects/git%2Bgithub.com%2Fypcrts%2Ffqdn.svg?type=shield :target: https://app.fossa.com/projects/git%2Bgithub.com%2Fypcrts%2Ffqdn?ref=badge_shield

.. |License Status...

Read as markdown · JSON record · Source repository · Homepage

AI interpretation — verify before relying

AI-generated interpretation of the package facts above; every digit, version, license, or vulnerability id it cites is grounded in the facts already shown on this page

Validates fully-qualified domain names (FQDNs) against RFC 1123 and related IETF specifications, with configurable strictness to allow relaxed hostname formats like those without periods or with underscores.

Low friction: pure Python wheel with a single lightweight runtime dependency (cached-property). Last release was 2021-03-11, now 1981 days old; repo remains active with recent commits (2025-03-05) and is not archived, suggesting maintenance despite aging status.

MPL 2.0 is a copyleft license requiring derivative works to disclose source and license under the same terms. If you modify fqdn itself, you must publish those changes under MPL 2.0; using it unmodified as a dependency typically poses no distribution burden.

Usage

pip install fqdn
from fqdn import FQDN
domain = FQDN('bbc.co.uk')
print(domain.is_valid)  # True
print(domain.absolute)  # 'bbc.co.uk.'

Verdict: A stable, low-friction FQDN validator with no known vulnerabilities and broad Python support (2.7, 3.5+). Aging maintenance (last release 2021) is offset by recent repo activity and production-grade status. MPL 2.0 copyleft applies only if you modify the package itself. Suitable for RFC-conformant hostname validation in DNS, email, and web contexts.

Needs verification

Whether the 1981-day gap since last release reflects intentional stability or reduced active maintenance.
Performance characteristics or benchmarks for large-scale validation workloads.
Compatibility of cached-property dependency across all declared Python versions (2.7–3.9+).

fqdn validationdomain name validatorrfc 1123 hostname checkdns hostname validationfully qualified domain name parserinternet hostname validatordomain name rfc compliance