Generate unique UUIDs and GUIDs in bulk
Built & maintained by Pappu Venkata Subbi Reddy, founder of Clacify
The UUID Generator creates cryptographically random Version 4 UUIDs (universally unique identifiers) — the 36-character identifiers (like 550e8400-e29b-41d4-a716-446655440000) used throughout software to uniquely label database rows, API resources, session tokens, and distributed-system objects without needing a central authority to hand out IDs. Generate one at a time or up to 100 at once, with an optional uppercase format, and copy individually or all together. Because it uses the Web Crypto API's cryptographically secure random source rather than a weak pseudo-random generator, the UUIDs this tool produces have the same collision-resistance guarantees as UUIDs generated by any production database or backend language's standard library.
Each UUID follows the standard 8-4-4-4-12 hexadecimal format defined by RFC 4122. Every character is drawn from crypto.getRandomValues(), a cryptographically secure pseudo-random number generator, except for two fixed positions: the version nibble (fixed to "4," identifying this as a Version 4/random UUID) and two bits of the variant nibble (fixed per the RFC to identify the UUID variant). With 122 truly random bits, the probability of ever generating the same UUID twice is astronomically small — RFC 4122 itself notes you would need to generate roughly a billion UUIDs per second for about 85 years before the probability of a single collision reached 50%. That is why Version 4 UUIDs are treated as effectively unique without any coordination between the systems generating them.
Auto-incrementing integer IDs (1, 2, 3…) work fine for a single database, but break down the moment you have multiple servers, offline clients, or merging datasets, because two different sources will both hand out "row 47" and collide the instant they're combined. A UUID sidesteps the entire problem: any system, anywhere, with no network connection and no coordination with any other system, can generate a UUID and be confident — not guaranteed, but confident to the point of being a non-issue in practice — that no other system has ever generated or will ever generate the same one. This is why UUIDs are the default primary-key choice in distributed databases, why every major cloud provider's resource IDs are UUIDs, and why offline-first mobile apps use them to create records that will merge safely once the device reconnects.
The UUID standard defines several versions with different generation strategies. Version 1 encodes the generating machine's MAC address and a timestamp — unique, but it leaks information about when and where the ID was created, which is a real privacy concern. Version 3 and Version 5 are deterministic: they hash a namespace and a name (MD5 for v3, SHA-1 for v5), so the same input always produces the same UUID — useful for generating a stable ID from an existing value like an email address, but not for producing an ID that's meant to be unpredictable. Version 4, which this tool generates, uses no input data at all beyond randomness — no timestamp, no machine identifier, no name to hash — which is why it's become the default choice for almost every general-purpose use case: it reveals nothing about its origin and requires nothing but a good random source.
Database primary keys and foreign keys in distributed or sharded systems; API resource identifiers (most REST APIs return a UUID, not a sequential integer, for exactly the reasons above); session and API tokens; idempotency keys, so a client can safely retry a request without the server processing it twice; and test-data seeding, where generating a batch of realistic-looking unique IDs quickly is genuinely useful — which is why this tool supports generating up to 100 at once rather than only one.
A UUID (Universally Unique Identifier) is a 128-bit identifier formatted as 8-4-4-4-12 hexadecimal characters (e.g. 550e8400-e29b-41d4-a716-446655440000). UUIDs are used as primary keys in databases instead of sequential integers to avoid collisions in distributed systems, as request IDs in microservices, and as file names for uploaded assets.
UUID and GUID (Globally Unique Identifier) refer to the same thing — a 128-bit unique identifier. UUID is the formal IETF standard (RFC 4122); GUID is Microsoft's term for the same concept used in Windows and .NET. They are interchangeable and use the same format.