Regex for UUID — Pattern Explained with Examples

In this tutorial, you'll learn about Regex for UUID. We cover key concepts, practical examples, and best practices to help you understand and apply this topic effectively.

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

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