UUID Generator

FREEUtilities

TOOLUUID Generator

00000000-0000-4000-8000-000000000000

Count:

v4 (random)

100% freeNo signupRuns in your browser

About UUID Generator

Universally Unique Identifiers (UUIDs) are 128-bit labels standardized in RFC 4122 that allow distributed systems to create identifiers without a central coordinator. UUID v4 draws all 122 non-fixed bits from a cryptographically secure random source, making each identifier statistically unique across space and time with no coordination between generators.

How It Works

The generator calls the Web Crypto API's crypto.getRandomValues() to fill a 16-byte typed array with cryptographically secure random data. Specific bits are then set to fixed values per the RFC 4122 v4 spec: bits 12–15 of the seventh byte are set to 0100 (version 4), and bits 6–7 of the ninth byte are set to 10 (variant 1).

The 16 bytes are then formatted into the canonical 8-4-4-4-12 hyphenated hexadecimal string (e.g., f47ac10b-58cc-4372-a567-0e02b2c3d479). This formatting is purely cosmetic — the actual uniqueness lives in the underlying 122 random bits.

For bulk generation, the same process runs in a tight loop. All UUIDs are generated synchronously in the browser — no network call is made, and the results exist only in your current page session.

Who Is This For

A Node.js developer generating primary keys for a PostgreSQL table of user records where auto-increment IDs would leak user count to API consumers.

A mobile app engineer creating client-side correlation IDs for API requests so log entries across microservices can be traced without a server round-trip.

A QA engineer generating 50 UUIDs at once to seed a test database with realistic-looking non-sequential record identifiers.

A product manager creating unique campaign tracking codes for 10 email variants without needing to query a database for the next available ID.

Scope note: UUID v4 is not sortable by creation time — if chronological ordering matters, use UUID v7 or ULID instead. Bulk generation above a few thousand UUIDs in a single session may fill the page memory; reload to reset. The generated UUIDs are not persisted — closing or refreshing the page clears all history.

How to Use

Click "Generate" to create a new UUID

Set the count (1-100) for bulk generation

Click any UUID to copy it to clipboard

Use "Copy All" to grab all generated UUIDs at once

Frequently Asked Questions

UUID v4 (random). These are generated using crypto.getRandomValues() for cryptographic randomness.

UUID v4 has 122 random bits, giving 5.3 x 10^36 possible values. The probability of collision is astronomically low — effectively zero for practical purposes.

UUID v1 is generated from the current timestamp plus the MAC address of the machine, making it time-ordered but potentially revealing about the host. UUID v4 is fully random and reveals nothing about the generating system — making it the preferred choice for most applications.

Yes, but be aware that random UUID v4 values cause index fragmentation in B-tree indexes over time. For high-write databases, consider UUID v7 (time-ordered) or ULID as alternatives. For most applications, UUID v4 as a primary key works perfectly well.

Statistically negligible. To have even a 50% chance of a collision, you would need to generate 2.71 quintillion UUIDs. At a rate of one billion UUIDs per second, that would take about 85 years.

UUID v4 is canonically lowercase with hyphens (e.g., 550e8400-e29b-41d4-a716-446655440000). Both uppercase and lowercase representations are valid per RFC 4122; most systems treat them as case-insensitive.