Credit Card Validation Regex (Visa)

Validate Visa credit card numbers starting with 4 and having 13 or 16 digits using regex pattern.

Pattern Breakdown

^4[0-9]{12}(?:[0-9]{3})?$

Components

Character Classes

• 4 - Literal 4 (Visa always starts with 4)
• [0-9] - Any digit 0-9
• {12} - Quantifier: exactly 12 occurrences
• (?:[0-9]{3})? - Optional group: 3 more digits for 16-digit cards

Examples

Valid:

• 4111111111111111 (16 digits)
• 4111111111111 (13 digits)
• 4000000000000 (13 digits)
• 4999999999999999 (16 digits)

Invalid:

• 5111111111111111 (starts with 5, MasterCard)
• 411111111111 (only 12 digits)
• 41111111111111111 (17 digits)
• 4-1111-1111-1111-1111 (contains formatting)
• 4111 1111 1111 1111 (contains spaces)

Implementation

JavaScript

const visaRegex = /^4[0-9]{12}(?:[0-9]{3})?$/;
visaRegex.test('4111111111111111'); // true
visaRegex.test('4111111111111'); // true (13 digits)
visaRegex.test('5111111111111111'); // false (MasterCard)
visaRegex.test('411111111111'); // false (only 12 digits)

// To handle formatted numbers, remove formatting first
const formatted = '4111-1111-1111-1111'.replace(/[-\s]/g, '');
visaRegex.test(formatted); // true

Python

import re
visa_regex = r'^4[0-9]{12}(?:[0-9]{3})?$'
bool(re.match(visa_regex, '4111111111111111'))  # True
bool(re.match(visa_regex, '4111111111111'))  # True (13 digits)
bool(re.match(visa_regex, '5111111111111111'))  # False (MasterCard)

# To handle formatted numbers
formatted = '4111-1111-1111-1111'.replace('-', '').replace(' ', '')
bool(re.match(visa_regex, formatted))  # True

Go

visaRegex := regexp.MustCompile(`^4[0-9]{12}(?:[0-9]{3})?$`)
visaRegex.MatchString("4111111111111111") // true
visaRegex.MatchString("4111111111111") // true (13 digits)
visaRegex.MatchString("5111111111111111") // false (MasterCard)

Limitations

1. No Luhn algorithm: Doesn't validate using Luhn checksum algorithm
2. No formatting: Doesn't accept formatted numbers (spaces, dashes)
3. Format only: Validates format, not actual card validity
4. No expiration/CVV: Doesn't validate expiration date or CVV
5. Security: Never store full card numbers, only last 4 digits

When to Use

• Initial format validation
• Quick card type detection
• Client-side validation (first pass)
• When you need to identify Visa cards

For production, consider:

• Implementing Luhn algorithm for checksum validation
• Supporting formatted input (remove spaces/dashes)
• Using payment processing libraries (Stripe, PayPal, etc.)
• Never storing full card numbers
• Server-side validation (never trust client-side only)
• PCI DSS compliance requirements