HTTP Strict-Transport-Security Header Regex for Python

What this pattern does

This page provides a well-structured, multi-part regular expression for matching http strict-transport-security header, ported and verified for Python. In security-sensitive code, using an unverified regex can open the door to both false positives and denial-of-service attacks. 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

# HTTP Strict-Transport-Security Header
# ReDoS-safe | RegexVault — Security > Security Headers

import re

http_stricttransportsecurity_header_pattern = re.compile(r'^max-age=([0-9]+)(?:;\s*includeSubDomains)?(?:;\s*preload)?$')

def validate_http_stricttransportsecurity_header(value: str) -> bool:
    return bool(http_stricttransportsecurity_header_pattern.fullmatch(value))

# Example
print(validate_http_stricttransportsecurity_header("max-age=31536000"))  # True

Test Cases

When to use this pattern

This pattern is drawn from the Security > Security Headers 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

HSTS tells browsers to only connect via HTTPS. min max-age for HSTS preloading: 31536000 (1 year). max-age=0 disables HSTS. includeSubDomains extends to all subdomains. preload submits to Chrome/Firefox preload lists — be careful, it is very hard to undo. Capture group 1: max-age value in seconds.