Credit Card Validation Regex (Discover)

Validate Discover credit card numbers starting with 6011 or 65 and having 16 digits using regex pattern.

Pattern Breakdown

^6(?:011|5[0-9]{2})[0-9]{12}$

Components

Detailed Breakdown

• 6 - Literal 6 (Discover starts with 6)
• (?:011|5[0-9]{2}) - Prefix alternation:
  • 011 - For cards starting with 6011
  • 5[0-9]{2} - For cards starting with 65xx (6500-6599)
• [0-9]{12} - Remaining 12 digits

Examples

Valid:

• 6011111111111111 (starts with 6011)
• 6500000000000000 (starts with 6500)
• 6555555555555555 (starts with 6555)
• 6599999999999999 (starts with 6599)

Invalid:

• 4111111111111111 (starts with 4, Visa)
• 601111111111111 (only 15 digits)
• 60111111111111111 (17 digits)
• 6400000000000000 (starts with 64, not Discover)
• 6-0111-1111-1111-1111 (contains formatting)

Implementation

JavaScript

const discoverRegex = /^6(?:011|5[0-9]{2})[0-9]{12}$/;
discoverRegex.test('6011111111111111'); // true
discoverRegex.test('6500000000000000'); // true
discoverRegex.test('4111111111111111'); // false (Visa)
discoverRegex.test('601111111111111'); // false (only 15 digits)

// To handle formatted numbers, remove formatting first
const formatted = '6011-1111-1111-1111'.replace(/[-\s]/g, '');
discoverRegex.test(formatted); // true

Python

import re
discover_regex = r'^6(?:011|5[0-9]{2})[0-9]{12}$'
bool(re.match(discover_regex, '6011111111111111'))  # True
bool(re.match(discover_regex, '6500000000000000'))  # True
bool(re.match(discover_regex, '4111111111111111'))  # False (Visa)

# To handle formatted numbers
formatted = '6011-1111-1111-1111'.replace('-', '').replace(' ', '')
bool(re.match(discover_regex, formatted))  # True

Go

discoverRegex := regexp.MustCompile(`^6(?:011|5[0-9]{2})[0-9]{12}$`)
discoverRegex.MatchString("6011111111111111") // true
discoverRegex.MatchString("6500000000000000") // true
discoverRegex.MatchString("4111111111111111") // false (Visa)

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
6. Limited prefixes: Discover also issues cards with other prefixes (622126-622925, 644-649, etc.) not covered

When to Use

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

For production, consider:

• Implementing Luhn algorithm for checksum validation
• Supporting additional Discover prefixes (622126-622925, 644-649, etc.)
• 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