What is a MAC Address Regex?

A MAC (Media Access Control) address is a unique identifier assigned to a device’s network interface. It typically looks like 01:23:45:67:89:AB or 01-23-45-67-89-AB, composed of six pairs of hexadecimal digits. This address is assigned to network interface controllers—such as WiFi adapters, Ethernet cards, and similar hardware—serving as a fingerprint that distinguishes each device on a local network.

To validate MAC addresses using regex, we use a pattern that ensures the correct grouping, delimiter, and character format.

MAC Address Regex Pattern (Python)

 ^([0-9A-Fa-f]{2}[:-]){5}([0-9A-Fa-f]{2})

This pattern validates:

• 6 hexadecimal pairs separated by either colons (:) or hyphens (-)

• Both uppercase and lowercase letters (A-F, a-f)

• Strict format with no extra characters

How to Validate MAC Address in Python

Here’s how you can use the re module in Python to validate MAC addresses:

import re

def is_valid_mac(mac):
    pattern = re.compile(r'^([0-9A-Fa-f]{2}[:-]){5}([0-9A-Fa-f]{2})$')
    return bool(pattern.match(mac))

# Example usage
macs = ["01:23:45:67:89:AB", "01-23-45-67-89-AB", "0123.4567.89AB"]
for mac in macs:
    print(f"{mac} => {is_valid_mac(mac)}")

Extracting a MAC Address from a String

To pull a MAC address from a larger chunk of text, you can use Python's re module with a suitable regular expression. Here’s how you might do it:

import re

def extract_mac_address(s):
    pattern = r'(?:[0-9A-Fa-f]{2}[:-]){5}[0-9A-Fa-f]{2}'
    return re.findall(pattern, s)

# Example usage
log_entry = "Unknown error in node 00:00:5e:00:53:af. Terminating."
found_macs = extract_mac_address(log_entry)
print(found_macs)  # Output: ['00:00:5e:00:53:af']

This approach will scan the text and return any MAC addresses it finds, making it useful when you need to extract such information from logs or unstructured messages.

Examples

Valid

• AA:BB:CC:DD:EE:FF

• aa-bb-cc-dd-ee-ff

  
  

Invalid

• AA:BB:CC:DD:EE

• AABB.CCDD.EEFF

• GG:HH:II:JJ:KK:LL

Use Cases

• IoT and Embedded Systems: Validate MAC addresses during device provisioning.

• Network Security: Filter and whitelist specific MAC formats in firewalls.

• Form Validation: Ensure valid MAC input in Python-based admin tools or APIs.

• Batch File Processing: Use alongside the Python Regex Tester for cleaning large datasets with device records.

Pro Tips

• Flexible Delimiters: If your input could contain both : and -, keep the current pattern. For one specific format only, remove the alternate.

• Case Insensitivity: This pattern works for both uppercase and lowercase letters. No need for .lower() conversions.

• Additional Check: Pair with the IP Address Regex Python Validator to fully verify network device entries.

• Avoid Typos: Add a pre-validation step to strip extra whitespace using .strip() in Python before applying the regex.