URL Percent-Encoding Validation Regex for Python

What this pattern does

This page provides a well-structured, multi-part regular expression for matching url percent-encoding validation, 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

# URL Percent-Encoding Validation
# ReDoS-safe | RegexVault — Web & Network > URL

import re

url_percentencoding_validation_pattern = re.compile(r'^(?:[a-zA-Z0-9\-._~!$&'()*+,;=:@/?#\[\]]|%[0-9a-fA-F]{2})*$')

def validate_url_percentencoding_validation(value: str) -> bool:
    return bool(url_percentencoding_validation_pattern.fullmatch(value))

# Example
print(validate_url_percentencoding_validation("/path/to%20resource"))  # True

Test Cases

When to use this pattern

This pattern is drawn from the Web & Network > URL 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

This pattern validates encoding structure, not meaning. %2F is technically valid encoding but may have semantic implications (encoded forward slash vs. path separator) that require application-level handling.