SHA-256 Hash Regex for Python

What this pattern does

This page provides a lightweight, single-purpose regular expression for matching sha-256 hash, 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

# SHA-256 Hash
# ReDoS-safe | RegexVault — Security > Password Formats

import re

sha256_hash_pattern = re.compile(r'^[a-f0-9]{64}$')

def validate_sha256_hash(value: str) -> bool:
    return bool(sha256_hash_pattern.fullmatch(value))

# Example
print(validate_sha256_hash("e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855"))  # True

Test Cases

When to use this pattern

This pattern is drawn from the Security > Password Formats 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

SHA-256 is part of the SHA-2 family, still cryptographically secure. Used for certificates, code signing, TLS, and file integrity. For password hashing, always use SHA-256 within a proper password hashing function (PBKDF2, Argon2) — raw SHA-256 alone is not suitable for passwords.