IPv6 Link-Local Address Regex for Python

What this pattern does

This page provides a comprehensive, battle-tested regular expression for matching ipv6 link-local address, 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

# IPv6 Link-Local Address
# ReDoS-safe | RegexVault — Web & Network > IPv6

import re

ipv6_linklocal_address_pattern = re.compile(r'^[Ff][Ee][89AaBb][0-9a-fA-F](?::[0-9a-fA-F]{0,4}){0,7}(?:%[a-zA-Z0-9_.-]{1,20})?$')

def validate_ipv6_linklocal_address(value: str) -> bool:
    return bool(ipv6_linklocal_address_pattern.fullmatch(value))

# Example
print(validate_ipv6_linklocal_address("fe80::1"))  # True

Test Cases

When to use this pattern

This pattern is drawn from the Web & Network > IPv6 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

The fe80::/10 block means the first 10 bits are 1111111010, which covers fe80 through febf. The [89AaBb] in position 3 covers the valid second-nibble range for this prefix.