Data
Generate version 4 UUIDs for use as unique identifiers in databases, APIs, files, or any system that needs universally unique values. Choose how many you need and how they should be formatted.
Generated output
Set options and click Generate to create UUIDs.
Version 4 UUIDs are generated using crypto.randomUUID(), which is available natively in modern browsers. The format follows RFC 4122: 32 hexadecimal digits displayed in five groups separated by hyphens (xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx). The "4" in the third group identifies the UUID version; the "8", "9", "a", or "b" in the fourth group identifies the variant.
You're adding a user record to a distributed database and need a stable identifier that requires no coordination between nodes. Generate a single standard v4 UUID like "f7a3c1d8-4e92-4b0f-a6d7-3e91c82f0b15" and use it as the primary key.
Answers to common questions about this generator and how it works.
UUID stands for Universally Unique Identifier. It is a 128-bit label used to identify information in computer systems. UUIDs are standardised by RFC 4122 and are widely used in databases, APIs, and distributed systems to identify records without a central registry.
Extremely unique. A v4 UUID has 122 bits of randomness, giving 5.3 x 10^36 possible values. The probability of generating two identical UUIDs, even across billions of systems generating thousands per second, is effectively zero in any practical scenario.
It depends. UUIDs are great for distributed systems where you need IDs without a central counter. The trade-off is larger storage size (16 bytes vs. 8 for a BIGINT) and potential index fragmentation with random v4 UUIDs. Sequential UUID variants (v7) help with this, though this generator currently produces v4 only.
Standard format is "xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx" — 36 characters including 4 hyphens. No-dash format removes the hyphens, giving a 32-character hex string. Both represent the same 128-bit value. Some systems prefer no-dash for compactness.
In theory, yes — they are random values. In practice, the probability is astronomically small. For a 50% chance of any collision, you would need to generate approximately 2.7 quadrillion UUIDs. You are safe to treat all generated UUIDs as unique.
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