Mastercard Number Regex for Python

What this pattern does

This page provides a well-structured, multi-part regular expression for matching mastercard 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

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

import re

mastercard_number_pattern = re.compile(r'^(?: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})$')

def validate_mastercard_number(value: str) -> bool:
    return bool(mastercard_number_pattern.fullmatch(value))

# Example
print(validate_mastercard_number("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 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

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.