OpenAI API Key Regex for Python

What this pattern does

This page provides a well-structured, multi-part regular expression for matching openai api key, 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

# OpenAI API Key
# ReDoS-safe | RegexVault — Security > API Keys & Tokens

import re

openai_api_key_pattern = re.compile(r'^sk-(?:proj-)?[A-Za-z0-9]{20}T3BlbkFJ[A-Za-z0-9]{20}$|^sk-[A-Za-z0-9_-]{20,128}$')

def validate_openai_api_key(value: str) -> bool:
    return bool(openai_api_key_pattern.fullmatch(value))

# Example
print(validate_openai_api_key("sk-aBcDeFgHiJkLmNoPqRsT3BlbkFJuVwXyZ0123456789AB"))  # True

Test Cases

When to use this pattern

This pattern is drawn from the Security > API Keys & Tokens 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

Older OpenAI keys use the sk-{48chars} format with 'T3BlbkFJ' (base64 for 'OpenAI') as a recognizable substring. Newer project-scoped keys use sk-proj- prefix. Both patterns are included.