UUID Generator

Generate random UUID v4 values with format options. 100% client-side.

Generated UUIDs
Click Generate to create UUID(s).

How to Use the UUID Generator

  1. Set the count — enter how many UUIDs you want to generate (1 to 100).
  2. Choose a format — lowercase (default), UPPERCASE, or no dashes.
  3. Click Generate — your UUIDs appear instantly in the output area.
  4. Copy or download — use Copy All to copy all UUIDs to your clipboard, or Download to save as a text file.

What Is a UUID?

A UUID (Universally Unique Identifier), also known as a GUID (Globally Unique Identifier), is a 128-bit identifier that is guaranteed to be unique across space and time. UUIDs are standardized by RFC 4122 and are used extensively in software development to identify resources, database records, distributed system nodes, and more, without requiring a central authority to coordinate ID assignment.

UUID Format

A standard UUID is represented as 32 hexadecimal digits grouped into five sections separated by hyphens, following the pattern 8-4-4-4-12. For example: 550e8400-e29b-41d4-a716-446655440000. The total string length is 36 characters (32 hex digits plus 4 hyphens). The version number is encoded in the 13th character, and the variant is encoded in the 17th character.

UUID Versions

  • Version 1 — based on timestamp and MAC address. Guarantees uniqueness but can leak the host machine's identity.
  • Version 3 — generated by MD5 hashing a namespace identifier and a name. Deterministic: the same inputs always produce the same UUID.
  • Version 4 — randomly generated using a cryptographically secure random number generator. This is the most commonly used version and what this tool generates.
  • Version 5 — similar to v3 but uses SHA-1 instead of MD5. Preferred over v3 for new applications.
  • Version 7 — a newer format (RFC 9562) that combines a Unix timestamp with random data, providing both uniqueness and sortability. Increasingly popular for database primary keys.

Why Use UUID v4?

UUID v4 is the most widely used version because it is simple, fast, and does not require any external state or network information. It uses 122 bits of randomness (6 bits are reserved for version and variant markers), making the probability of collision negligibly small. You would need to generate approximately 2.71 quintillion UUIDs to have a 50% chance of a single duplicate. This makes v4 UUIDs ideal for distributed systems where nodes cannot coordinate ID generation. For other randomness-based tools, check out our Hash Generator and Password Generator.

Common Use Cases

  • Database primary keys — avoid auto-increment conflicts in distributed databases
  • API resource identifiers — use UUIDs in REST API URLs for non-sequential, non-guessable IDs
  • Session tokens — generate unique session identifiers for web applications
  • File naming — create unique filenames for uploads to avoid collisions
  • Message queues — assign unique identifiers to messages in distributed systems
  • Correlation IDs — trace requests across microservices using a shared UUID

UUID in Different Languages

Most programming languages have built-in UUID support: Python's uuid.uuid4(), Java's UUID.randomUUID(), JavaScript's crypto.randomUUID(), C#'s Guid.NewGuid(), Ruby's SecureRandom.uuid, and Go's uuid.New() from the google/uuid package. This tool uses the browser's Web Crypto API for cryptographically secure random generation. If you need time-based identifiers alongside UUIDs, our Timestamp Converter can help with epoch-based ID schemes.

Frequently Asked Questions

A UUID (Universally Unique Identifier) is a 128-bit number used to uniquely identify information in computer systems. UUIDs are formatted as 32 hexadecimal digits displayed in five groups separated by hyphens (e.g., 550e8400-e29b-41d4-a716-446655440000). They are also known as GUIDs (Globally Unique Identifiers) in Microsoft ecosystems.
UUID v4 is a randomly generated UUID. All 128 bits (except 6 bits for the version and variant fields) are filled with random data from a cryptographically secure random number generator. This makes collisions extremely unlikely — the probability of generating two identical v4 UUIDs is approximately 1 in 5.3 x 10^36.
While not mathematically guaranteed to be unique, UUID v4 values are generated from 122 random bits, making collisions astronomically unlikely. You would need to generate about 2.71 quintillion UUIDs to have a 50% chance of a single collision. For all practical purposes, they are unique.
No. UUIDs are generated entirely in your browser using the Web Crypto API (crypto.randomUUID or crypto.getRandomValues). No data is sent to any server. There is no logging and no data collection.
UUID (Universally Unique Identifier) and GUID (Globally Unique Identifier) refer to the same concept. UUID is the term used in the RFC 4122 standard and most programming contexts, while GUID is the term commonly used in Microsoft technologies like .NET, SQL Server, and Windows. They are interchangeable.