UUID/GUID Generator

Generate universally unique identifiers (UUIDs/GUIDs) in multiple versions. All generated locally in your browser using the crypto.getRandomValues() API.

How It Works

A UUID (Universally Unique Identifier), also known as a GUID (Globally Unique Identifier), is a 128-bit identifier standardized by RFC 9562. UUIDs are formatted as 32 hexadecimal characters separated by hyphens: xxxxxxxx-xxxx-Mxxx-Nxxx-xxxxxxxxxxxx, where M indicates the version and N indicates the variant.

UUID Versions

• Version 1 (Timestamp): Encodes the current timestamp (100-nanosecond intervals since October 15, 1582) along with a clock sequence and node identifier. Reveals creation time.
• Version 3 (MD5): Deterministic. Generated by hashing a namespace UUID and a name with MD5. Same inputs always produce the same UUID.
• Version 4 (Random): The most widely used. Contains 122 bits of cryptographically secure random data. Best for general purpose.
• Version 5 (SHA-1): Like v3 but uses SHA-1 instead of MD5. Preferred over v3 for new applications.
• Version 6 (Reordered Time): Like v1 but with the timestamp fields reordered so UUIDs sort chronologically. A bridge between v1 and v7.
• Version 7 (Sortable): Uses a Unix timestamp in milliseconds followed by random bits. UUIDs sort chronologically, making them ideal for database primary keys.

Common Use Cases

• Database primary keys: Use v7 for sortable keys, v4 for general purpose
• API identifiers: Expose UUIDs instead of sequential IDs to prevent enumeration
• Distributed systems: Generate unique IDs across multiple nodes without coordination
• Deterministic IDs: Use v3 or v5 when you need the same UUID for the same input every time
• Correlation IDs: Trace requests across microservices

UUID vs Other Identifiers

• UUID vs Auto-increment: UUIDs work across distributed systems without a central authority, but are larger (16 bytes vs 4-8 bytes).
• UUID vs ULID: ULIDs are lexicographically sortable like UUIDv7 but use Crockford's Base32 for a more compact representation.
• UUID vs Snowflake ID: Snowflake IDs (used by Twitter/Discord) are 64-bit, sortable, and include a machine ID, but require central configuration.