Regex for UUID — Pattern Explained with Examples

UUID (Universally Unique Identifier) validation is essential for systems that use them as primary keys, session tokens, or distributed identifiers. UUIDs follow the 8-4-4-4-12 hex format with specific bits indicating the version and variant. This pattern validates the format and enforces correct version and variant bits.

The Pattern

/^[0-9a-fA-F]{8}-[0-9a-fA-F]{4}-[1-5][0-9a-fA-F]{3}-[89abAB][0-9a-fA-F]{3}-[0-9a-fA-F]{12}$/

Pattern Breakdown

Matches

• 550e8400-e29b-41d4-a716-446655440000 (UUID v4)
• 00000000-0000-0000-0000-000000000000 (nil UUID)
• f47ac10b-58cc-4372-a567-0e02b2c3d479 (UUID v4)
• 6ba7b810-9dad-11d1-80b4-00c04fd430c8 (UUID v1)
• 00112233-4455-6677-8899-aabbccddeeff

Does NOT Match

• 550e8400-e29b-z1d4-a716-446655440000 (invalid hex character z)
• 550e8400e29b41d4a716446655440000 (missing hyphens)
• 550e8400-e29b-41d4-a716-4466554400000 (13 hex digits in last group)
• 550e8400-e29b-41d4-a716 (truncated)
• not-a-uuid (text)

Language Examples

JavaScript

const uuidRegex = /^[0-9a-fA-F]{8}-[0-9a-fA-F]{4}-[1-5][0-9a-fA-F]{3}-[89abAB][0-9a-fA-F]{3}-[0-9a-fA-F]{12}$/;
console.log(uuidRegex.test('550e8400-e29b-41d4-a716-446655440000')); // true
console.log(uuidRegex.test('not-a-uuid'));                            // false

Python

import re
pattern = r'^[0-9a-fA-F]{8}-[0-9a-fA-F]{4}-[1-5][0-9a-fA-F]{3}-[89abAB][0-9a-fA-F]{3}-[0-9a-fA-F]{12}$'
print(bool(re.match(pattern, '550e8400-e29b-41d4-a716-446655440000')))  # True
print(bool(re.match(pattern, 'not-a-uuid')))                             # False

Java

import java.util.regex.Pattern;

public class UuidValidator {
    private static final Pattern UUID_PATTERN =
        Pattern.compile("^[0-9a-fA-F]{8}-[0-9a-fA-F]{4}-[1-5][0-9a-fA-F]{3}-[89abAB][0-9a-fA-F]{3}-[0-9a-fA-F]{12}$");

    public static boolean isValid(String uuid) {
        return UUID_PATTERN.matcher(uuid).matches();
    }
}

Common Pitfalls

• The version digit at position 13 determines UUID version (v1, v2, v3, v4, v5) — this pattern enforces 1-5, rejecting invalid version values like 0 or 6
• The variant bits at position 17 must be in the range 8-b — this pattern enforces RFC 4122 compliant variants
• Some systems include curly braces around UUIDs (e.g. {550e8400-...}) — strip or add optional braces in the pattern if needed
• The nil UUID (00000000-0000-0000-0000-000000000000) is valid and passes this pattern despite having version 0 — version 0 is actually not one of the five RFC versions, so some patterns exclude it

Real-World Use Cases

• API request validation — validate UUID path parameters and request body identifiers in RESTful services
• Database constraint checking — verify primary key formats before insert or batch import operations
• Session token validation — ensure session UUIDs stored in cookies or tokens are well-formed before performing lookups

FAQ

Related Patterns

Regex for Credit Card Numbers Regex for Email