Mastercard Number Regex for Go

What this pattern does

This page provides a well-structured, multi-part regular expression for matching mastercard number, ported and verified for Go. 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 Go project — whether you're validating in a Gin handler, a gRPC service, or a command-line tool.

Go Implementation

// Mastercard Number
// ReDoS-safe | RegexVault — Finance > Card Numbers

package validation

import "regexp"

var mastercardNumberRe = regexp.MustCompile(`^(?:5[1-5][0-9]{14}|2(?:2[2-9][1-9]|[3-6][0-9]{2}|7[01][0-9]|720)[0-9]{12})$`)

func ValidateMastercardNumber(s string) bool {
    return mastercardNumberRe.MatchString(s)
}

// Example
// fmt.Println(ValidateMastercardNumber("5500005555555559")) // 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 Go developers because Go's RE2 engine is inherently safe from catastrophic backtracking, but this pattern has been additionally verified for correctness. 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

Mastercard expanded their BIN range in 2017 to include 2221-2720. The 51-55 range is the original BIN prefix. Always strip separators before matching.