Docker Registry URL Regex for Python

What this pattern does

This page provides a well-structured, multi-part regular expression for matching docker registry url, ported and verified for Python. A rigorously tested regex reduces debugging time and protects your application from edge-case failures. The snippet below is ready to drop into your Python project — whether you're validating in a Django view, a FastAPI endpoint, or a standalone data processing script.

Python Implementation

# Docker Registry URL
# ReDoS-safe | RegexVault — Dev & Systems > Docker

import re

docker_registry_url_pattern = re.compile(r'^(?:[a-z0-9][a-z0-9\-]*\.)+[a-z]{2,63}(?::[1-9][0-9]{0,4})?$')

def validate_docker_registry_url(value: str) -> bool:
    return bool(docker_registry_url_pattern.fullmatch(value))

# Example
print(validate_docker_registry_url("docker.io"))  # True

Test Cases

When to use this pattern

This pattern is drawn from the Dev & Systems > Docker category and carries a ReDoS-safe certification. That matters for Python developers because particularly important in Python web servers where CPU-bound regex operations can stall concurrent request handling. RegexVault audits patterns against known backtracking attack vectors, ensuring you have the necessary context before using this regex in a high-stakes production environment.

Common Pitfalls

Technical Notes

Docker registry URLs do not include a scheme in image references. Port 5000 is the default for private registry deployments. 'localhost' is a Docker special case not matched by this pattern.