A UUID (Universally Unique Identifier) is a 128-bit identifier that is guaranteed to be unique across space and time. UUIDs are commonly used as database primary keys, API identifiers, session tokens, and distributed system identifiers.

What is the difference between UUID v4 and v1?

UUID v4 is randomly generated, making it the most common choice for general-purpose unique IDs. UUID v1 is time-based and includes the MAC address of the generating machine. UUID v5 is name-based using SHA-1 hashing of a namespace and a name.

Are UUIDs guaranteed to be unique?

For all practical purposes, yes. The probability of generating two identical UUID v4 values is approximately 1 in 5.3 x 10^36 — effectively zero. You would need to generate 1 billion UUIDs per second for 85 years to have a 50% chance of one collision.

UUID v5 is a name-based UUID that uses SHA-1 hashing. Given the same namespace and name, it always produces the same UUID — making it deterministic and reproducible. It is useful for generating consistent IDs for the same resource across systems.

Can I generate UUIDs without dashes?

Yes. This tool lets you toggle between standard format (with dashes), compact format (without dashes), braces format, and URN format. You can also choose uppercase or lowercase output.

UUID Generator

Generate, validate & format UUIDs — v1, v4, v5, bulk up to 1000, with download

Instant | 100% client-side

UUID Version

Randomly generated using crypto.getRandomValues(). Best for general-purpose unique identifiers.

Simulated time-based UUID using the current timestamp (100-ns intervals since Oct 15, 1582) with a random clock sequence and node.

Deterministic SHA-1 name-based UUID. Same namespace + name always produces the same UUID. Uses crypto.subtle.digest().

Namespace UUID

Name

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Format Options

Output Format

Letter Case

Bulk Generate

Quantity (1–1000)

Set a quantity and click Generate to bulk-create UUIDs

UUID Validator & Parser

UUID Versions

v4 Fully random — most common. Best for general-purpose unique IDs with maximum privacy.
v1 Timestamp + random node. Useful for time-ordering and debugging. Simulated MAC address.
v5 Deterministic SHA-1 name-based. Same namespace + name always yields the same UUID.

Quick Tips

Click the UUID display to copy it instantly
Use v5 to generate deterministic IDs from a name (e.g. domain names, emails)
Use compact format for URL-safe, storage-efficient IDs
Generate up to 1,000 UUIDs at once and download as TXT or CSV
Use the Validator to check format and detect UUID version

UUID Anatomy

xxxxxxxx-xxxx-4xxx-axxx-xxxxxxxxxxxx

xxxxxxxx = time_low (v1) / random
4 = version digit (position 13)
a = variant bits (8, 9, a, or b)
Total: 128 bits / 32 hex chars

100% Private

All UUIDs are generated locally in your browser using the Web Crypto API (crypto.subtle for v5). Nothing is sent to any server.

What Is a UUID?

Understanding Universally Unique Identifiers and why they matter

A UUID (Universally Unique Identifier) is a 128-bit identifier standardized by RFC 9562. UUIDs are designed to be globally unique without requiring a central authority — any system can generate one independently with virtually zero chance of collision.

UUIDs are widely used as database primary keys, API resource identifiers, session tokens, file names, distributed system identifiers, and message queue IDs. The format consists of 32 hexadecimal characters displayed in five groups separated by hyphens: xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx.

A GUID (Globally Unique Identifier) is Microsoft's term for the same concept. The terms UUID and GUID are completely interchangeable — they refer to identical data structures and generation algorithms.

Database Keys

UUIDs are perfect primary keys for distributed databases where auto-increment IDs cause conflicts. They work seamlessly across sharded and replicated systems.

API Resources

Exposing sequential IDs in APIs is a security risk. UUIDs make resource identifiers unpredictable and safe to share in URLs without revealing system internals.

Distributed Systems

In microservices and event-driven architectures, UUIDs allow any service to create unique IDs independently without coordination or central registries.

UUID Version Comparison

Choose the right UUID version for your use case

Feature	v1	v4	v5
Source	Timestamp + Node	Cryptographic random	SHA-1 (namespace+name)
Deterministic	No	No	Yes
Sortable	Partially	No	No
Privacy	Leaks timestamp	Fully private	Name-dependent
Collision risk	Very low	Extremely low	Zero (same input)
Best for	Time-ordered IDs	General purpose	Named/stable IDs

Frequently Asked Questions

Common questions about UUIDs and GUIDs

A UUID (Universally Unique Identifier) is a 128-bit identifier formatted as 32 hexadecimal characters in five groups: xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx. UUIDs are designed to be globally unique without a central authority, making them ideal for distributed systems, databases, and APIs.

UUID v4 is entirely randomly generated — the most common and recommended version for general use. UUID v1 combines a timestamp with a node identifier, encoding when and where it was created. UUID v5 is deterministic: given the same namespace and name it always produces the same output using SHA-1 hashing, making it ideal for consistent resource identifiers.

For all practical purposes, yes. A UUID v4 has 122 random bits, giving 5.3 × 10³⁶ possible values. To reach a 50% collision probability, you would need to generate approximately 2.71 × 10¹⁸ UUIDs — equivalent to generating 1 billion UUIDs per second for 85 years.

GUID (Globally Unique Identifier) is Microsoft's term for UUID. They are functionally identical — a GUID follows the same RFC standard as UUID. The terms are completely interchangeable in all contexts.

Use UUID v5 when you need a stable, repeatable identifier derived from a known name, such as a domain name, email address, or resource path. Because v5 is deterministic, the same input always produces the same UUID across any system or language that implements the spec correctly.

Yes. Use the Format Options panel to switch between standard (with dashes), compact (no dashes), braces (for .NET/Windows), or URN format (urn:uuid:...). You can also toggle between lowercase and UPPERCASE output. All bulk UUIDs respect the same format settings.

After bulk-generating UUIDs, click the TXT or CSV download buttons that appear. TXT downloads one UUID per line; CSV wraps each UUID in a row with an index column — both are UTF-8 encoded for maximum compatibility.