UUID/GUID Generator
Generate universally unique identifiers for your applications and systems.
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How to Use the UUID/GUID Generator
A UUID (Universally Unique Identifier), also known as a GUID (Globally Unique Identifier), is a 128-bit number used to identify information in computer systems. This tool provides a simple and fast way to generate UUIDs according to standard specifications.
Simply click the "Generate New UUID" button to create a new identifier. You can then easily copy it to your clipboard for use in databases, software development, or any other application requiring unique IDs.
- Version 4 (Random): Generated from purely random or pseudo-random numbers. This is the most common type of UUID used.
- Version 1 (Timestamp): Generated from a timestamp and a node ID (usually the MAC address). This version can be useful for time-series data but may expose information about when and where it was created.
Complete Guide to UUID/GUID
What is a UUID/GUID?
A UUID (Universally Unique Identifier) or GUID (Globally Unique Identifier) is a 128-bit number used to uniquely identify information in computer systems. The probability of a randomly generated UUID being duplicated is so small that it's considered negligible.
The standard format of a UUID consists of 32 hexadecimal characters, divided into 5 groups separated by hyphens: 8-4-4-4-12. For example: 550e8400-e29b-41d4-a716-446655440000.
UUIDs are defined by RFC 4122 and are used in many contexts: databases, distributed systems, session identifiers, and much more.
Different UUID versions
UUID Version 1: Based on timestamp and MAC address. Useful for chronological sorting but can reveal information about the machine and creation time. Guarantees uniqueness but at the cost of privacy.
UUID Version 4: Generated completely randomly (122 bits of randomness). This is the most commonly used version as it reveals no information about its origin. The collision risk is approximately 1 in 2^122.
UUID Version 5 and 3: Generated from a namespace and name via SHA-1 (v5) or MD5 (v3). Useful when you need to deterministically generate the same UUID from the same inputs.
Common use cases
Database primary keys: UUIDs allow generating unique identifiers without central coordination, ideal for distributed databases or offline applications that sync later.
Session identifiers and tokens: UUID v4s are perfect for session tokens as they're unpredictable and reveal no information about the user or system.
File systems and storage: Many systems use UUIDs to uniquely identify disk partitions, volumes, and files.
UUID vs auto-incremented identifiers
Auto-incremented identifiers (1, 2, 3...) are simple but have drawbacks: they reveal the number of records, allow guessing adjacent IDs, and cause problems in distributed systems.
UUIDs solve these problems: they reveal nothing about the data, are impossible to guess, and can be generated independently on multiple servers without collision risk.
However, UUIDs are larger (16 bytes vs 4-8 for an integer) and less performant for indexing. The choice depends on your application's specific needs.
Security and privacy
UUID v1s contain the MAC address and timestamp, which can be a privacy concern. An attacker can determine when and on which machine a UUID was created.
UUID v4s are cryptographically random and reveal no information. They're recommended for any security-sensitive use like authentication tokens.
While UUIDs are unique, they're not secret by default. Never use them as the only security mechanism without additional validation.
Performance and storage
A UUID takes 16 bytes in binary format or 36 characters in text format (with hyphens). That's 4 times more than a 32-bit integer.
In databases, UUIDs can affect indexing performance because they're random and don't allow sequential insertion. Some databases offer optimized UUID types.
For very high-performance applications, consider alternatives like UUID v1 (sortable) or hybrid formats like ULID (Universally Unique Lexicographically Sortable Identifier).
Implementation best practices
Always use your language's standard libraries rather than implementing your own generator. Built-in generators use cryptographically secure entropy sources.
Store UUIDs in binary format (16 bytes) rather than text (36 characters) to save space and improve performance.
If you expose UUIDs in URLs, ensure they're not the only access control mechanism. Always validate permissions server-side.
Alternatives to UUID
ULID (Universally Unique Lexicographically Sortable Identifier): Combines a timestamp and randomness, allowing chronological sorting while remaining unique.
Snowflake ID (Twitter): 64-bit format with timestamp, machine ID, and sequence. More compact but requires coordination.
NanoID: Shorter and customizable alternative to UUIDs, using a custom alphabet to reduce length while maintaining uniqueness.