GUID Generator Online

A UUID (Universally Unique Identifier) is a 128-bit identifier formatted as 8-4-4-4-12 hexadecimal groups. It is designed to be globally unique across all systems without central coordination. UUIDs are widely used as database primary keys, request IDs, and file names.

v1 encodes the MAC address and a timestamp — sequential but leaks hardware identity. v4 is completely random (122 random bits) — the most widely used version for its simplicity and privacy. v7 (RFC 9562) uses a millisecond Unix timestamp prefix plus random bits — lexicographically sortable, making it ideal for database primary keys that need both uniqueness and time-ordering.

Yes. GUID (Globally Unique Identifier) is Microsoft's name for UUID (Universally Unique Identifier). Both follow the same RFC 4122 standard and are interchangeable. GUIDs are typically written in uppercase with braces {550E8400-...} while UUIDs are written lowercase without braces, but the underlying format is identical.

Extremely unlikely. With 122 random bits, you would need to generate approximately 2.71 quintillion UUIDs (2.71 × 10¹⁸) before the probability of a collision reaches 50%. In practice, generating a billion UUIDs per second for 85 years would produce that many. UUID collisions are a theoretical concern but not a practical one.

Prefer v7 for new databases. v7's timestamp prefix means rows are inserted in roughly chronological order, which keeps B-tree index pages hot and reduces page splits — a significant performance win for high-write tables. v4's random distribution causes random index page access and higher write amplification. UUID v4 is fine for low-write tables or when you already use it consistently.