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MAC Address Validation Regex

• CronOS Team
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MAC Address Validation Regex

Validate MAC addresses in standard format with 6 groups of 2 hexadecimal digits separated by colons or hyphens.

Pattern Breakdown

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

Components

ComponentDescriptionMatches
^Start anchorEnsures match from string start
([0-9A-Fa-f]{2}[:-]){5}First 5 groupsExactly 5 groups of 2 hex digits + separator
([0-9A-Fa-f]{2})Final groupLast group of 2 hex digits (no trailing separator)
$End anchorEnsures match to string end

Character Classes

  • [0-9A-Fa-f] - Hexadecimal digits: 0-9, A-F, a-f
  • {2} - Quantifier: exactly 2 occurrences
  • {5} - Quantifier: exactly 5 occurrences
  • [:-] - Separator: colon or hyphen
  • () - Capturing groups for structure

Examples

Valid:

  • 00:1B:44:11:3A:B7
  • 00-1B-44-11-3A-B7
  • 00:1b:44:11:3a:b7 (lowercase)
  • 00:1B:44:11:3A:B7
  • FF:FF:FF:FF:FF:FF (broadcast address)

Invalid:

  • 00:1B:44:11:3A (only 5 groups)
  • 00:1B:44:11:3A:B7:C8 (7 groups)
  • 00:1B:44:11:3A:B (last group incomplete)
  • 00:1B:44:11:3A:GB (invalid hex character)
  • 00 1B 44 11 3A B7 (spaces not supported)
  • 001B44113AB7 (no separators)

Implementation

JavaScript

javascript
const macRegex = /^([0-9A-Fa-f]{2}[:-]){5}([0-9A-Fa-f]{2})$/;
macRegex.test('00:1B:44:11:3A:B7'); // true
macRegex.test('00-1B-44-11-3A-B7'); // true
macRegex.test('00:1B:44:11:3A'); // false (incomplete)
macRegex.test('00:1B:44:11:3A:GB'); // false (invalid hex)

Python

python
import re
mac_regex = r'^([0-9A-Fa-f]{2}[:-]){5}([0-9A-Fa-f]{2})$'
bool(re.match(mac_regex, '00:1B:44:11:3A:B7'))  # True
bool(re.match(mac_regex, '00-1B-44-11-3A-B7'))  # True
bool(re.match(mac_regex, '00:1B:44:11:3A'))  # False (incomplete)

Go

go
macRegex := regexp.MustCompile(`^([0-9A-Fa-f]{2}[:-]){5}([0-9A-Fa-f]{2})$`)
macRegex.MatchString("00:1B:44:11:3A:B7") // true
macRegex.MatchString("00-1B-44-11-3A-B7") // true
macRegex.MatchString("00:1B:44:11:3A") // false (incomplete)

Limitations

  1. Mixed separators: Doesn't prevent mixing colons and hyphens (e.g., 00:1B-44:11-3A:B7)
  2. No space support: Doesn't support space-separated format
  3. No dot notation: Doesn't support Cisco-style dot notation (e.g., 0000.1b44.113a)
  4. Format only: Validates format, not actual MAC address validity
  5. No multicast/broadcast validation: Doesn't check for special MAC addresses

When to Use

  • MAC address format validation
  • Network device configuration
  • Hardware address input forms
  • Network management systems
  • When you need standard MAC format checking

For production, consider:

  • Supporting space-separated format if needed
  • Supporting dot notation for Cisco devices
  • Preventing mixed separators
  • Validating multicast/broadcast addresses if required
  • Normalizing to a single format for storage

Need to generate a regex pattern?

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