JSON Web Token (JWT) Regex for Python

What this pattern does

This page provides a well-structured, multi-part regular expression for matching json web token (jwt), 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

# JSON Web Token (JWT)
# ReDoS-safe | RegexVault — Web & Network > Misc

import re

json_web_token_jwt_pattern = re.compile(r'^[A-Za-z0-9\-_]+\.[A-Za-z0-9\-_]+\.[A-Za-z0-9\-_]*$')

def validate_json_web_token_jwt(value: str) -> bool:
    return bool(json_web_token_jwt_pattern.fullmatch(value))

# Example
print(validate_json_web_token_jwt("eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJzdWIiOiIxMjM0NTY3ODkwIiwibmFtZSI6IkpvaG4gRG9lIiwiaWF0IjoxNTE2MjM5MDIyfQ.SflKxwRJSMeKKF2QT4fwpMeJf36POk6yJV_adQssw5c"))  # True

Test Cases

When to use this pattern

This pattern is drawn from the Web & Network > Misc 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 signature section may be empty for unsigned tokens (alg: none). NEVER use alg: none in production — always validate algorithm. This regex validates structure only, not cryptographic validity.