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A UUID (Universally Unique Identifier) is a 128-bit identifier formatted as a 32-character hexadecimal string divided into five groups by hyphens — for example: 550e8400-e29b-41d4-a716-446655440000. UUIDs are designed to be globally unique across all systems and databases, making them ideal for identifying records, sessions, transactions, files, and any other entities where uniqueness must be guaranteed without central coordination.

UUID v1 is generated from the current timestamp and the device's MAC address, making it time-ordered but potentially traceable to the generating machine. UUID v4 is generated from random numbers — it has no connection to time or hardware, making it the most commonly used version for general purposes. UUID v5 is generated from a namespace and a name using SHA-1 hashing, always producing the same UUID for the same input — useful for deterministic identifiers.

UUID v4 uses 122 bits of randomness, which means the probability of generating two identical UUIDs is astronomically small — roughly 1 in 5.3 × 10^36. In practical terms, you would need to generate billions of UUIDs per second for trillions of years before a collision becomes statistically likely. For all real-world use cases, UUID v4 values can be treated as unique.

Sequential integer IDs (1, 2, 3...) are simple and fast but have limitations: they reveal information about your data volume, they require a central counter (which causes bottlenecks in distributed systems), and they make it easy for users to guess other IDs. UUIDs are better when you need to generate IDs across multiple servers without coordination, when you want to prevent enumeration of records, or when merging databases from different sources.

Yes. UUIDs are generated using the Web Crypto API, which provides cryptographically secure random numbers. This is the same source of randomness used in professional security applications. The generated UUIDs are suitable for database primary keys, API tokens, session identifiers, and any other production use case.

Yes. The bulk generation feature lets you generate up to 100 UUIDs in a single operation. All generated UUIDs are displayed in a copyable list, making it easy to use them in database seeds, test fixtures, configuration files, or any scenario where you need a batch of unique identifiers at once.

No. All UUID generation happens entirely in your browser using JavaScript and the Web Crypto API. The UUIDs you generate are never sent to any server, never logged, and never stored anywhere outside your current browser session. Once you close the tab, there is no record of any UUID that was generated.

UUID v5 generates a deterministic UUID from a namespace and a name — meaning the same namespace + name combination always produces the exact same UUID. This is useful when you need a stable, repeatable identifier for a known entity — for example, generating a consistent UUID for a URL, an email address, or a product SKU. Unlike v4, v5 is not random; it is a hash-based identifier tied to its input.