Regex to Match MAC Addresses

This regex matches MAC (Media Access Control) addresses in their standard notation. Here is the token-by-token breakdown:

( — Opens a capturing group for the first five pairs of hex digits, each followed by a separator.

[0-9a-fA-F]{2} — A character class matching exactly two hexadecimal digits. It includes digits 0-9, lowercase a-f, and uppercase A-F. Each pair represents one byte of the six-byte MAC address.

[:-] — A character class matching either a colon or a hyphen. MAC addresses are commonly written with either separator style: AA:BB:CC:DD:EE:FF or AA-BB-CC-DD-EE-FF. This class accepts both formats.

){5} — Closes the capturing group and repeats it exactly five times. This matches the first five byte-pairs, each with a trailing separator.

[0-9a-fA-F]{2} — Matches the sixth and final byte-pair of two hexadecimal digits, without a trailing separator.

The g flag enables global matching to find all MAC addresses in the text, and the i flag makes the hex letters case-insensitive. Note that this pattern allows mixed separators (e.g., AA:BB-CC:DD-EE:FF), which is technically non-standard. If strict consistency is needed, you would use two separate patterns or a backreference. This pattern covers the most common MAC address formats used in networking tools, DHCP configurations, and device identification.