Credit Card Regex Go Validator

What is Credit Card Regex?

In Go, credit card regex is a pattern-based method used to quickly check if a card number follows the format rules of known card issuers like Visa, MasterCard, and American Express.

It’s a first line of defense in web forms and payment integrations to ensure users input the correct type of card before deeper backend verification.

You can validate:

• Visa (starts with 4)

• MasterCard (starts with 51–55 or 2221–2720)

• American Express (starts with 34 or 37)

Credit Card Regex Patterns (with Samples)

These patterns validate length, structure, and prefix rules based on the issuer.

// Visa
^4[0-9]{12}(?:[0-9]{3})?$
// Matches: 4111111111111 or 4111111111111111

// MasterCard
^(5[1-5][0-9]{14}|2[2-7][0-9]{14})$
// Matches: 5555555555554444, 2223000048400011

// Amex
^3[47][0-9]{13}$
// Matches: 371449635398431

How to Validate Credit Card Numbers in Go

Here’s a Go example to validate a Visa card using regex:

package main

import (
    "fmt"
    "regexp"
)

func isValidVisa(card string) bool {
    visaRegex := regexp.MustCompile(`^4[0-9]{12}(?:[0-9]{3})?$`)
    return visaRegex.MatchString(card)
}

func main() {
    testCard := "4111111111111111"
    fmt.Printf("Is '%s' a valid Visa card? %t\n", testCard, isValidVisa(testCard))
}

Want to support multiple card types?

You can define a map of regexes for each issuer and switch based on the prefix.

Common Use Cases

• Checkout Pages: Prevent incorrect card number entries before API submission.

• Form Validation: Highlight invalid input early for better UX.

• Banking Apps: Quick verification during KYC or card linking.

• Data Cleansing: Validate card fields in customer or transaction datasets.

  
  

Pro Tips

• Use regex for format validation only. Use Luhn’s algorithm for checksum validation.

• Strip spaces and hyphens from user input before applying regex.

• Pre-compile your regex in Go using MustCompile() for performance.

• Mask card numbers after validation when displaying to users.

• Keep issuer-specific regexes separate for better maintainability.

Combine with These Tools

Maximize test coverage and input validation by using:

• API Key Generator – For generating secure access to payment systems

• Email Regex Go Validator – Validate customer email during checkout

• Phone Number Regex Go Validator – Ensure correct contact info

• UUID Regex Go Validator – Tag each card entry with a unique transaction ID

• Password Regex Go Validator – Validate secure login credentials