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UUID v4 Generator

Generate version 4 UUIDs using random numbers. The most common type with 122 random bits.

Configuration

Generated UUIDs

Click 'Generate' to create UUIDs

Generate UUID version 4

Format

UUID v4 uses random numbers:

xxxxxxxx-xxxx-4xxx-[89ab]xxx-xxxxxxxxxxxx

The 4 in the third group indicates version 4. The [89ab] in the fourth group is a variant indicator.

Structure

  • Random bits: 122 bits of cryptographically secure random numbers
  • Version: 4 bits set to 0100 (version 4)
  • Variant: 2 bits set to 10 (RFC 4122 variant)

Worked example

A typical UUID v4:

550e8400-e29b-41d4-a716-446655440000
  • 550e8400-e29b-4 = random (with version 4 indicator)
  • 1d4-a716 = random
  • 446655440000 = random

Note the "4" in the third group showing version 4.

How to use

  1. Click "Generate" to create a new UUID v4
  2. Copy the result
  3. Repeat for multiple UUIDs

Random generation

UUID v4 uses 122 random bits:

  • 32 bits: first group
  • 16 bits: second group
  • 12 bits: third group (plus 4 version bits)
  • 14 bits: fourth group (plus 2 variant bits)
  • 48 bits: fifth group

Advantages

  • Truly random: No predictable pattern
  • Privacy-safe: No information about the generator
  • ** Cryptographically secure**: Hard to guess or reproduce
  • No coordination needed: Each generation is independent

Disadvantages

  • Not sortable: Random order makes chronological sorting impossible
  • No metadata: Cannot determine when or where it was generated
  • Collision risk: Theoretically possible, though extremely unlikely

Collision probability

With 122 random bits, the probability of collision is:

  • 1 in 2^61 after 1 billion UUIDs
  • 1 in 2^31 after 1 trillion UUIDs
  • Effectively zero for practical applications

Common use cases

  • Database primary keys
  • Session IDs
  • API tokens
  • Temporary identifiers
  • Any unique ID requirement

FAQ

Is UUID v4 truly unique? Practically yes. The collision probability is astronomically low.

How many UUIDs can I generate? Effectively unlimited. 2^122 possible values.

Can I predict the next UUID? No, v4 uses cryptographically secure random numbers.

Should I use v4 for security tokens? Yes, v4 is the standard for security tokens and session IDs.

What about sorting? v4 UUIDs cannot be sorted chronologically. Use v1 if you need ordering.

Are all v4 UUIDs valid? Yes, as long as the version and variant bits are set correctly.

Other related tools

SoonUUID / GUID GeneratorGenerate universally unique identifiers (UUIDs/GUIDs). Supports v1, v3, v4, v5, and v7 with bulk generation and formatting options.internalgenerator