What is a UUID and why is it used?

A UUID (Universally Unique Identifier) is a 128-bit number used to uniquely identify information in computer systems. It is standardized by RFC 4122 and provides a way to generate identifiers that are unique across space and time without requiring a central registration authority. UUIDs are commonly used as database primary keys, API resource identifiers, session tokens, and in distributed systems where unique identification is critical.

What is the difference between UUID v4 and UUID v1?

UUID v1 is time-based: it uses the current timestamp, clock sequence, and a node ID (usually the MAC address) to generate unique identifiers. UUID v4 is randomly generated using random or pseudo-random numbers. UUID v4 is the most commonly used version because it does not expose the time or machine information, making it more privacy-friendly. v1 is useful when you need UUIDs that can be chronologically sorted or when you need to identify the generating machine.

What are UUID v3 and v5, and how are they different?

UUID v3 and v5 are both name-based UUIDs: they generate deterministic UUIDs by hashing a namespace identifier and a name string. UUID v3 uses MD5 hashing (128-bit), while UUID v5 uses SHA-1 hashing (160-bit, truncated to 128 bits). SHA-1 is generally preferred over MD5 for security reasons. The key property of name-based UUIDs is that the same namespace + name combination always produces the same UUID, making them ideal for generating consistent identifiers from known data.

Are the generated UUIDs truly unique?

UUIDs are designed to be unique across space and time. The probability of a collision is extremely low — for UUID v4 (random), there are approximately 5.3 x 10^36 possible values. To put this in perspective, you would need to generate about 1 billion UUIDs per second for 85 years to have a 50% chance of a single collision. For practical purposes, UUIDs can be considered unique for most applications.

Is my data safe when using this UUID generator?

Yes, absolutely. All UUID generation is performed locally in your browser using the industry-standard uuid library. No data, including any names or namespaces you enter, is transmitted to any server. The tool works entirely client-side and also functions offline after the initial page load. Your privacy and security are fully protected.

UUID Generator Online - Generate UUID v1, v3, v4, v5 & NIL UUIDs Instantly

A UUID Generator is a tool that creates Universally Unique Identifiers (UUIDs) — 128-bit values used to uniquely identify information in computer systems. UUIDs are standardized by the RFC 4122 specification and are widely used in databases, distributed systems, API development, and software applications to ensure unique identification without a central coordinating authority. Our free online UUID generator supports all major UUID versions — v1 (time-based), v3 (MD5 hash), v4 (random), v5 (SHA-1 hash), and the NIL UUID. Whether you need a single identifier or batch generation of multiple UUIDs, this tool provides instant, reliable results entirely within your browser.

Key Features

Multi-Version Support

Generate UUID v1 (time-based), v3 (MD5 hash), v4 (random), v5 (SHA-1 hash), and NIL UUID

Batch Generation

Generate 1 to 50 UUIDs simultaneously with a single click

v3/v5 Name & Namespace

Create deterministic UUIDs using namespace presets (DNS, URL, OID, X.500) or custom UUID namespaces with name input

Custom Namespace

Input any valid UUID as a custom namespace with real-time validation

One-Click Copy

Copy all generated UUIDs to clipboard instantly

Instant Refresh

Generate new UUID sets with a single click

Client-Side Processing

All computation happens in your browser — zero data upload

No Data Upload

Everything runs in your browser; nothing is sent to a server

Practical Use Cases

Database Primary Keys

Generate unique identifiers for database records across distributed systems

API Development

Create unique resource identifiers for RESTful APIs and microservices

Session & Token Management

Generate session IDs, CSRF tokens, and correlation IDs

Software Development

Use as unique identifiers in application code, logs, and event tracking

Distributed Systems

Ensure conflict-free identifiers across multiple nodes without central coordination

Testing & QA

Quickly generate test data with unique identifiers for load testing and integration testing

How to Use the UUID Generator

Select a Version
Choose from NIL, v1 (time-based), v3 (MD5 hash), v4 (random), or v5 (SHA-1 hash)
Set Quantity
Use the slider to choose how many UUIDs to generate (1 to 50)
Configure v3/v5 (optional)
For v3 and v5 versions, select a namespace preset (DNS, URL, OID, X.500) or enter a custom namespace UUID, then provide a name string
Copy Results
Click the Copy button to copy all generated UUIDs to your clipboard, or click Refresh to generate a new set

💡 Pro Tip: All processing is done locally in your browser. Your data never leaves your device.

Frequently Asked Questions About UUIDs

What is a UUID and why is it used?: A UUID (Universally Unique Identifier) is a 128-bit number used to uniquely identify information in computer systems. It is standardized by RFC 4122 and provides a way to generate identifiers that are unique across space and time without requiring a central registration authority. UUIDs are commonly used as database primary keys, API resource identifiers, session tokens, and in distributed systems where unique identification is critical.
What is the difference between UUID v4 and UUID v1?: UUID v1 is time-based: it uses the current timestamp, clock sequence, and a node ID (usually the MAC address) to generate unique identifiers. UUID v4 is randomly generated using random or pseudo-random numbers. UUID v4 is the most commonly used version because it does not expose the time or machine information, making it more privacy-friendly. v1 is useful when you need UUIDs that can be chronologically sorted or when you need to identify the generating machine.
What are UUID v3 and v5, and how are they different?: UUID v3 and v5 are both name-based UUIDs: they generate deterministic UUIDs by hashing a namespace identifier and a name string. UUID v3 uses MD5 hashing (128-bit), while UUID v5 uses SHA-1 hashing (160-bit, truncated to 128 bits). SHA-1 is generally preferred over MD5 for security reasons. The key property of name-based UUIDs is that the same namespace + name combination always produces the same UUID, making them ideal for generating consistent identifiers from known data.
Are the generated UUIDs truly unique?: UUIDs are designed to be unique across space and time. The probability of a collision is extremely low — for UUID v4 (random), there are approximately 5.3 x 10^36 possible values. To put this in perspective, you would need to generate about 1 billion UUIDs per second for 85 years to have a 50% chance of a single collision. For practical purposes, UUIDs can be considered unique for most applications.
Is my data safe when using this UUID generator?: Yes, absolutely. All UUID generation is performed locally in your browser using the industry-standard uuid library. No data, including any names or namespaces you enter, is transmitted to any server. The tool works entirely client-side and also functions offline after the initial page load. Your privacy and security are fully protected.

What is a UUID Generator?