UUID v4 (Universally Unique Identifier version 4) is a 128-bit random identifier formatted as 32 hexadecimal characters in groups of 8-4-4-4-12, separated by hyphens. The version nibble is always 4 and the variant nibble is 8, 9, a, or b.

Is my data uploaded to a server?

No. UUID generation and validation happen entirely in your browser using the Web Crypto API (crypto.randomUUID()). Nothing leaves your device.

What is the probability of a UUID collision?

Practically zero. UUIDs v4 have 122 random bits, giving roughly 5.3 × 10^36 possible values. Even generating one billion UUIDs per second for a century, the collision probability is negligible.

What format options are available?

Standard (8-4-4-4-12 with hyphens, lowercase), no-hyphens (32 hex chars), and uppercase variants of both. All formats represent the same identifier.

Can I generate multiple UUIDs at once?

Yes. Use the bulk generator to produce 1 to 50 UUIDs in a single click. Copy all of them to the clipboard at once with the "Copy all" button.

UUID Generator — Free Online UUID v4 Generator & Validator

What is a UUID?

A UUID (Universally Unique Identifier) is a 128-bit number used to uniquely identify information without a central authority. The standard format is 32 hexadecimal digits in five groups separated by hyphens: xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx. This tool generates UUID v4, which uses random or pseudo-random numbers.

How to Use

Choose a count (1, 5, 10, 20, or 50) and click Generate
Select format options: remove hyphens, or switch to uppercase
Click Copy all to copy every UUID to your clipboard at once
Use the Validator field below to check whether any UUID is valid

All generation and validation happens locally in your browser — nothing is sent to a server.

UUID v4 Format

A UUID v4 looks like this:

550e8400-e29b-41d4-a716-446655440000
│        │    │    │    │
│        │    │    │    └── Node (48 bits)
│        │    │    └─────── Clock seq + variant (16 bits, first nibble = 8/9/a/b)
│        │    └──────────── Time hi + version (16 bits, first nibble = 4)
│        └───────────────── Time mid (16 bits)
└────────────────────────── Time low (32 bits)

In v4, both the “time” fields and “node” field are random. Only the version nibble (4) and the variant nibble (8, 9, a, or b) are fixed.

Format Options

Option	Example
Standard	`550e8400-e29b-41d4-a716-446655440000`
No hyphens	`550e8400e29b41d4a716446655440000`
Uppercase	`550E8400-E29B-41D4-A716-446655440000`
Uppercase + no hyphens	`550E8400E29B41D4A716446655440000`

All four representations carry the same unique identity — choose based on your system’s requirements.

Common Use Cases

Database primary keys: UUIDs avoid auto-increment collisions in distributed systems
API resource identifiers: safe to expose in URLs without revealing record counts
Idempotency keys: uniquely identify a request to avoid duplicate processing
File naming: collision-free names for uploaded files or generated assets
Session tokens: short-lived random tokens for authentication flows

UUID Collision Probability

UUID v4 has 122 random bits (the other 6 are version/variant). The probability of generating a duplicate UUID even after producing 1 billion UUIDs per second for 100 years is less than 50%. For practical purposes, treat UUIDs as globally unique.

Privacy

This tool uses the browser’s built-in crypto.randomUUID() API, which is cryptographically secure and requires no network calls. Your UUIDs are generated on your device and never leave it.

UUID vs ULID vs NanoID

	UUID v4	ULID	NanoID
Sortable	No	Yes (time-based)	No
URL-safe	With encoding	Yes	Yes
Standardized	RFC 4122	Community	Community
Length	36 chars	26 chars	21 chars (default)

UUID v4 is the safest default for database PKs and inter-system identifiers. Choose ULID if you need lexicographic sort order. Choose NanoID for shorter, URL-safe identifiers.

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