IPv6 in URL Bracket Notation Regex for Python

What this pattern does

This page provides a well-structured, multi-part regular expression for matching ipv6 in url bracket notation, 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 in URL Bracket Notation
# ReDoS-safe | RegexVault — Web & Network > IPv6

import re

ipv6_in_url_bracket_notation_pattern = re.compile(r'^\[(?:[0-9a-fA-F]{0,4}:){2,7}[0-9a-fA-F]{0,4}\]$')

def validate_ipv6_in_url_bracket_notation(value: str) -> bool:
    return bool(ipv6_in_url_bracket_notation_pattern.fullmatch(value))

# Example
print(validate_ipv6_in_url_bracket_notation("[2001:db8::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

IPv6 addresses in URLs must be in square brackets per RFC 2732. This pattern uses a simplified compressed IPv6 match — it accepts the major forms but may allow some technically invalid compressed sequences. For strict validation, pair with full IPv6 validation (net-ipv6-02) after stripping the brackets.