UUID Generator

Generate UUID v4 identifiers online. Bulk generate up to 25 UUIDs with options for uppercase, lowercase, and with or without hyphens.

Count:

Case:

Hyphens:

Generated UUID

46283f5f-69a6-4851-8be6-04213a66897a

Validate UUID

UUID to Validate

UUID v4 Format

xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx

4 = version number (always 4 for UUID v4)

y = variant (8, 9, a, or b)

x = random hex digit (0-9, a-f)

About UUIDs

A UUID (Universally Unique Identifier) is a 128-bit identifier that is practically unique across all systems without requiring a central authority. UUID v4 is generated using cryptographically secure random numbers.

UUID v4 has 122 random bits, giving approximately 5.3 x 10^36 possible values. The probability of generating a duplicate is astronomically small -- you would need to generate about 2.71 quintillion UUIDs to have a 50% chance of a collision.

UUIDs are commonly used as database primary keys, API request identifiers, session tokens, and anywhere globally unique IDs are needed. This tool uses the native crypto.randomUUID() API, which provides cryptographically secure random generation in your browser.

How to Use This UUID Generator

This tool generates cryptographically random UUID v4 identifiers directly in your browser. No data is sent to any server, and each UUID is generated using the Web Crypto API for high-quality randomness.

Generate a UUID — click the generate button to create a new random UUID v4. Each click produces a fresh, unique identifier.
Configure format options — toggle between uppercase and lowercase output, and choose whether to include hyphens in the UUID string.
Bulk generate — need multiple UUIDs at once? Use the bulk generation feature to create up to hundreds of UUIDs in a single click.
Copy the result — click the copy button to copy the generated UUID (or all bulk UUIDs) to your clipboard for use in your code, database, or configuration.

UUIDs generated here are compliant with RFC 4122 version 4. They contain 122 bits of randomness, with 6 bits reserved for the version and variant fields that identify them as v4 UUIDs.

Common Use Cases

Database primary keys — Use UUIDs as primary keys in PostgreSQL, MySQL, or MongoDB to generate unique IDs without auto-increment coordination across distributed systems.
Distributed systems — Generate globally unique identifiers across microservices, serverless functions, and edge workers without a central ID authority.
API request tracking — Assign a UUID to each API request as a correlation ID for tracing requests through logs, queues, and services.
Session identifiers — Create cryptographically random session IDs for user authentication, shopping carts, and temporary state management.
File and resource naming — Generate unique filenames for uploads, temporary files, and cloud storage objects to avoid naming conflicts.

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Frequently Asked Questions

What is a UUID?

A UUID (Universally Unique Identifier) is a 128-bit identifier that is practically unique across all systems without requiring a central authority. UUIDs are formatted as 32 hexadecimal digits displayed in five groups separated by hyphens, such as 550e8400-e29b-41d4-a716-446655440000.

What is the difference between UUID v4 and UUID v1?

UUID v4 is generated using random or pseudo-random numbers, making it the most commonly used version for general purposes. UUID v1 is based on the current timestamp and the MAC address of the generating machine, which can expose hardware information. UUID v4 is preferred when privacy and simplicity matter.

What is the probability of a UUID collision?

UUID v4 uses 122 random bits, giving approximately 5.3 x 10^36 possible values. The probability of generating a duplicate is astronomically low. You would need to generate about 2.71 quintillion UUIDs to have a 50% chance of a single collision, making collisions practically impossible.

How long is a UUID?

A UUID is 128 bits (16 bytes). In its standard string representation with hyphens, it is 36 characters long (32 hexadecimal digits plus 4 hyphens). Without hyphens, it is 32 characters long.

What is the difference between UUID and GUID?

UUID and GUID (Globally Unique Identifier) are effectively the same thing. GUID is the term used by Microsoft, while UUID is the standard term defined in RFC 4122. Both refer to the same 128-bit identifier format and are interchangeable.

Should I use UUIDs as database primary keys?

UUIDs work well as primary keys in distributed systems where you need to generate IDs without coordinating with a central database. However, random UUIDs can cause index fragmentation in B-tree indexes. Consider UUID v7 (time-ordered) or ULID for better database performance while keeping global uniqueness.

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