Tools
UUID Generator
The UUID generator creates universally unique identifiers in versions 1, 4, and 5 of the UUID specification (RFC 4122). Version 4 is the most common and uses cryptographic randomness. Version 1 embeds a timestamp and MAC address. Version 5 is deterministic and derived from a namespace and name using SHA-1. Bulk generation and formatting options are included.
What is a UUID?
A UUID (Universally Unique Identifier) is a 128-bit label standardized by RFC 4122 and displayed as 32 hexadecimal digits in five groups separated by hyphens (e.g., 550e8400-e29b-41d4-a716-446655440000). UUIDs are designed so that any two independently generated UUIDs are virtually guaranteed to be unique without coordination between systems. They are widely used as primary keys in databases, identifiers in distributed systems, and correlation IDs in logging. The specification defines several versions with different generation methods.
How does it work?
Select the UUID version you need. For v4, the tool generates 122 random bits using the browser's cryptographically secure random number generator and sets the version and variant bits. For v1, it combines the current timestamp with a random node identifier (since real MAC addresses are not accessible from a browser). For v5, you provide a namespace UUID and a name string, and the tool produces a deterministic SHA-1-based UUID. You can generate up to hundreds of UUIDs at once and copy them as a list.
Typical Use Cases
- Generating primary keys for database records in a distributed system
- Creating unique session tokens or correlation IDs for application logging
- Producing deterministic v5 UUIDs for consistent naming of well-known resources
- Generating test fixture IDs for automated integration tests
Step-by-step Guide
- Step 1: Select the UUID version (v1, v4, or v5).
- Step 2: For v5, enter a namespace UUID and a name string.
- Step 3: Set the number of UUIDs to generate.
- Step 4: Click Generate and copy the result.
Example
Input
UUID v4, quantity: 1
Output
f47ac10b-58cc-4372-a567-0e02b2c3d479
Tips & Notes
- Use UUID v4 for general-purpose unique identifiers where randomness is sufficient.
- Use UUID v5 when you need to generate the same UUID deterministically from a given input, such as namespaced resource identifiers.
- Store UUIDs as binary(16) in MySQL for better index performance instead of as a varchar(36).
Frequently Asked Questions
Can two UUID v4 values ever be the same?
Theoretically yes, but the probability is negligible. With 122 bits of randomness, you would need to generate about 2.7 × 10^18 UUIDs to have a 50% chance of a single collision.
What is the NIL UUID?
The NIL UUID is all zeros (00000000-0000-0000-0000-000000000000) and is used as a placeholder or null value where a UUID is required but no identity is intended.
UUID Generator
Generate Universally Unique Identifiers (UUIDs) of versions v1, v4, and v7 with configurable format and batch generation (up to 100 UUIDs).
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