What is the difference between UUID v4 and UUID v7?

UUID v4 is generated using entirely random values, making it the most commonly used version for general-purpose unique identification. UUID v7 embeds a Unix timestamp in the first 48 bits, making it chronologically sortable and significantly better for database primary keys since it reduces index fragmentation and improves query performance.

Can UUID values ever collide or duplicate?

While theoretically possible, the probability of a UUID v4 collision is astronomically low — approximately 1 in 2^122 (5.3 x 10^36). You would need to generate about 2.71 quintillion UUIDs to have a 50% chance of a single collision. In practice, UUID collisions are considered virtually impossible.

Are generated UUIDs safe to use for security-sensitive purposes?

UUID v4 uses cryptographically secure random number generators (crypto.getRandomValues in browsers), making them suitable for session tokens and similar uses. However, UUID v7 includes a timestamp component, so it reveals when it was created and should not be used where timing information must remain secret.

Why would I choose UUID v7 over v4 for database keys?

UUID v7 is preferred for database primary keys because its timestamp prefix ensures that new IDs are roughly sequential. This dramatically improves B-tree index performance, reduces page splits, and enables natural chronological ordering without needing a separate timestamp column.

What does removing hyphens do and when should I use it?

Removing hyphens produces a compact 32-character hexadecimal string instead of the standard 36-character hyphenated format. This is useful when integrating with systems that do not support hyphens in identifiers, reducing storage requirements, or when using UUIDs in URLs where hyphens might cause issues.

UUID Generator - UUID v4 v7 Bulk Generate | Free Online Tool

Settings

UUID Version

Fully random UUID - most common

Count

Generate up to 100 at once

Uppercase

Remove Hyphens

What is UUID?

UUID (Universally Unique Identifier) is a globally unique 128-bit identifier. Widely used for database primary keys, session IDs, filenames, etc.

UUID v4 (Random)

Fully random generation
Most commonly used
Extremely low collision probability

UUID v7 (Timestamp)

Timestamp + random
Chronologically sortable
Better for DB indexing

UUID Format

xxxxxxxx-xxxx-Mxxx-Nxxx-xxxxxxxxxxxx

M: version (4 or 7), N: variant (8, 9, a, b)

What is a UUID Generator?

A UUID (Universally Unique Identifier) Generator is a tool that creates globally unique 128-bit identifiers following the RFC 9562 standard. UUIDs are essential in distributed systems where unique identification is required without a central coordinating authority. They consist of 32 hexadecimal digits displayed in five groups separated by hyphens (e.g., 550e8400-e29b-41d4-a716-446655440000). With an astronomically low probability of collision, UUIDs are the industry standard for generating unique keys across databases, APIs, and microservices.

Generate UUID v4 (random) and v7 (timestamp-based) identifiers
Bulk generation of up to 100 UUIDs at once
Customizable output with uppercase and hyphen-free options
One-click copy for individual or all generated UUIDs
Fully client-side generation with no data sent to servers
Compliant with RFC 9562 (formerly RFC 4122) specification

How to Use

1
Select UUID Version
Choose between UUID v4 (fully random, most widely used) or UUID v7 (timestamp-based, sortable and optimized for database indexing).
2
Configure Options
Set the number of UUIDs to generate (1-100), toggle uppercase output, or remove hyphens for compact format.
3
Generate UUIDs
Click the Generate button to create your UUIDs instantly. All generation happens in your browser using cryptographically secure random values.
4
Copy Results
Click the copy button next to any individual UUID, or use Copy All to copy the entire list to your clipboard.

Frequently Asked Questions

Tips & Best Practices

Use UUID v7 for database primary keys to get better indexing performance and natural chronological ordering.
Use UUID v4 when you need maximum randomness and do not require sortability, such as for API tokens or session identifiers.
Store UUIDs as native UUID types in your database (e.g., PostgreSQL uuid type) rather than as strings to save storage and improve performance.
When displaying UUIDs to users, keep the hyphenated format for readability; use the compact format only for internal system identifiers.
Never use UUIDs as a substitute for proper authentication or authorization tokens — they are identifiers, not secrets.