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UUID Generator (v4)

Generate random version 4 UUIDs instantly — one or up to 50 at a time — using your browser's cryptographically secure random number generator.

Last updated

How to use the UUID Generator

  1. Get a UUID instantly

    A new UUID is generated as soon as the page opens. Click it to copy.

  2. Generate more

    Click Generate, or press Ctrl + Enter (Cmd + Enter on Mac), to create new UUIDs.

  3. Choose how many

    Select 1, 5, 10, 25 or 50 to generate UUIDs in bulk.

  4. Pick a format

    Toggle uppercase, hyphens and braces, then copy one, copy all or download them.

Features

  • A fresh UUID generated as soon as the page opens
  • Generate 1, 5, 10, 25 or 50 UUIDs at once
  • Format options: uppercase, with or without hyphens, and wrapped in braces
  • Click a UUID to copy it, copy all of them at once, or download them as a .txt file
  • Keyboard shortcuts: Ctrl/Cmd + Enter generates new UUIDs, Ctrl/Cmd + S downloads them
  • Uses crypto.randomUUID(), the browser's cryptographically secure generator

Are the UUIDs generated on a server?

No. UUIDs are generated in your browser with crypto.randomUUID(), which draws on your operating system's cryptographically secure random source. They're never sent to or logged by a server.

Read the DevNest privacy policy

Examples

  • Standard format

    Lowercase with hyphens — the format recommended by the UUID standard.

    Options

    Uppercase: off · Hyphens: on · Braces: off

    UUID

    f47ac10b-58cc-4372-a567-0e02b2c3d479

  • Microsoft GUID style

    Uppercase and wrapped in braces, as often shown by Microsoft tools.

    Options

    Uppercase: on · Hyphens: on · Braces: on

    UUID

    {F47AC10B-58CC-4372-A567-0E02B2C3D479}

  • Compact (no hyphens)

    32 hexadecimal characters, handy for file names or systems that don't accept hyphens.

    Options

    Uppercase: off · Hyphens: off · Braces: off

    UUID

    f47ac10b58cc4372a5670e02b2c3d479

Understanding UUIDs

What is a UUID?

A UUID (Universally Unique Identifier) is a 128-bit identifier, standardized in RFC 9562, written as 32 hexadecimal digits in five groups (8-4-4-4-12). UUIDs let independent systems create identifiers without coordinating with each other, with a negligible chance of two ever being the same. GUID is Microsoft's name for the same thing.

What is UUID v4?

Version 4 UUIDs are generated from random numbers: 122 of the 128 bits are random, and the remaining 6 bits record the version and variant. Unlike version 1 (based on a timestamp and hardware address) or version 7 (time-ordered), a v4 UUID reveals nothing about when or where it was created.

UUID v4 structure

xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx
f47ac10b-58cc-4372-a567-0e02b2c3d479

The first digit of the third group is always 4 — the version. The first digit of the fourth group (y) is always 8, 9, a or b — the variant. Every other digit is random.

When should you use UUIDs?

  • Database keys for records created in several places, or offline, before they reach a central database
  • Public identifiers in URLs and APIs, where sequential IDs would reveal how many records exist or let people guess other IDs
  • Request IDs, correlation IDs and idempotency keys for APIs and logs
  • Unique file names, test fixtures and seed data

If database index performance matters, consider time-ordered UUID v7 for primary keys, because random v4 values are inserted in random order. DevNest generates v4 UUIDs.

UUID vs auto-increment ID

AspectUUID v4Auto-increment ID
Generated byAny system, independentlyThe database, one at a time
Size128 bits (36 characters as text)Usually 32 or 64 bits
GuessableNo — randomYes — sequential
Reveals record countNoYes
Index localityPoor (random order)Excellent (sequential)

Frequently asked questions

How do I generate multiple UUIDs at once?

Choose 5, 10, 25 or 50 under How many. The list updates immediately, and you can copy all of them or download them as a text file, one per line.

What is the difference between a UUID and a GUID?

They are the same thing. GUID (Globally Unique Identifier) is the name Microsoft uses. Microsoft tools often show GUIDs in uppercase and wrapped in braces, which you can enable with the Uppercase and Braces options.

Should UUIDs be uppercase or lowercase?

The standard recommends lowercase output and says UUIDs should be compared case-insensitively. Use uppercase only if a system you're working with expects it.

Can two generated UUIDs ever be the same?

In theory yes, but the chance is astronomically small: you would need to generate about a billion UUIDs per second for about 86 years to reach a 50% chance of a single duplicate.

Should I use a UUID as a password or secret token?

No. UUIDs are designed to be unique identifiers, not secrets. Use a dedicated secure token or password generator for anything that grants access.