Visa Card Number Regex for Python

What this pattern does

This page provides a lightweight, single-purpose regular expression for matching visa card number, ported and verified for Python. Financial data validation has zero tolerance for false negatives — a missed invalid entry can corrupt downstream calculations. 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

# Visa Card Number
# ReDoS-safe | RegexVault — Finance > Card Numbers

import re

visa_card_number_pattern = re.compile(r'^4[0-9]{12}(?:[0-9]{3})?$')

def validate_visa_card_number(value: str) -> bool:
    return bool(visa_card_number_pattern.fullmatch(value))

# Example
print(validate_visa_card_number("4111111111111111"))  # True

Test Cases

When to use this pattern

This pattern is drawn from the Finance > Card Numbers 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

Visa uses prefix 4. 13-digit Visa cards are legacy (some still in circulation). 16-digit is standard. Luhn validation required separately. Input should have spaces/hyphens stripped before matching.