Regex to Validate UUIDs

This regex validates Universally Unique Identifiers (UUIDs) in their standard string representation. Here is the token-by-token breakdown:

^ — Anchors the match at the start of the string.

[0-9a-f]{8} — Matches the first group of exactly eight hexadecimal digits. UUIDs use lowercase hex digits (though the i flag makes this case-insensitive).

• — Matches a literal hyphen separator between groups.

[0-9a-f]{4} — Matches the second group of exactly four hex digits.

• — Another hyphen separator.

[1-7] — Matches the version digit. This is the first digit of the third group and indicates the UUID version. Valid versions are 1 through 7, covering time-based (v1), DCE security (v2), MD5 hash (v3), random (v4), SHA-1 hash (v5), sortable time-based (v6), and Unix epoch time-based (v7).

[0-9a-f]{3} — Matches the remaining three hex digits of the third group.

• — Another hyphen separator.

[89ab] — Matches the variant digit. The first digit of the fourth group indicates the UUID variant. Values 8, 9, a, or b indicate the standard RFC 4122 variant.

[0-9a-f]{3} — Matches the remaining three hex digits of the fourth group.

• — Another hyphen separator.

[0-9a-f]{12} — Matches the fifth and final group of exactly twelve hex digits.

$ — Anchors the match at the end.

The i flag makes matching case-insensitive, accepting both uppercase and lowercase hex digits. This pattern is essential for validating UUIDs in APIs, databases, and distributed systems.