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UUID Generator

Generate one or many cryptographically-random UUIDs (v4) in seconds.

  • uuid
  • guid
  • identifier
  • random

About UUID Generator

A UUID (Universally Unique Identifier, sometimes called a GUID in Microsoft-land) is a 128-bit value formatted as five groups of hex digits separated by hyphens, like 550e8400-e29b-41d4-a716-446655440000. The v4 variant is the one people usually mean: 122 of the 128 bits are random, which gives such an astronomical address space that collisions are practically impossible in any realistic workload.

That's why UUIDs are the default choice for primary keys, request IDs, file names, and anywhere else you need an identifier that can be generated independently on multiple machines without coordination and still be expected to be unique forever.

How to use

Pick how many UUIDs you need (up to 500) and choose a format: standard lowercase, UPPERCASE, no hyphens (32-character hex), or wrapped in {braces} for C#/.NET-style GUIDs.

Click "Generate" to produce a fresh batch — each click creates new values; nothing is stored. Copy individual UUIDs with the button on their row, or use "Copy all" to grab the whole list at once, one per line. UUIDs use crypto.randomUUID() under the hood, which is RFC 4122 v4 backed by the browser's cryptographic random source.

Frequently asked questions

  • How likely are two UUIDs to collide?

    Astronomically unlikely. A v4 UUID has 122 random bits, so there are 2¹²² ≈ 5.3 × 10³⁶ possible values. You'd need to generate around 2.7 × 10¹⁸ UUIDs before the probability of any collision reaches 50% — more than a billion per second for a hundred years. For all practical purposes, treat collisions as impossible.

  • What's the difference between UUID v4 and other versions?

    v4 is fully random (the most common general-purpose choice). v1 includes a timestamp and MAC address — useful but can leak the generating machine's identity. v3 and v5 are deterministic hashes of a name plus namespace, so the same input always gives the same UUID. v7 is a newer time-ordered variant designed for database index locality. This generator produces v4.

  • Is a UUID the same as a GUID?

    Yes — GUID ("Globally Unique Identifier") is Microsoft's name for the same thing, and the formats are interchangeable. The {braces} format option in this generator is the convention some .NET and Visual Studio APIs use; the other formats are universal.

  • Can I use UUIDs as primary keys in a database?

    Yes, very commonly. UUIDs let multiple services generate IDs independently without coordinating, which is impossible with auto-incrementing integers. The trade-off is index size and locality: UUID indexes are larger and less cache-friendly than 8-byte integers. v7 (time-ordered) UUIDs mitigate this; v4 (random) UUIDs are slower for inserts at very high write rates but fine for typical applications.

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