What is a UUID v4 and Why is it Cryptographically Secure?
A Universally Unique Identifier (UUID), also known as a Globally Unique Identifier (GUID), is a 128-bit identifier standardized by RFC 4122. Version 4 UUIDs are generated using cryptographically strong pseudo-random numbers, producing identifiers in the canonical 36-character hexadecimal format 8-4-4-4-12 (such as 9b1deb4d-3b7d-4bad-9bdd-2b0d7b3dcb6d).
With 122 random bits, the probability of generating a duplicate UUID v4 is so infinitesimally small that collisions are practically impossible across distributed databases, API keys, and microservices. This bulk generator uses the browser's native Web Crypto API for secure, high-entropy tokens.
How to Use This UUID Generator (3-Step Quick Guide)
Choose Quantity & Options
Select how many UUIDs you need (1 to 100) and choose uppercase/lowercase, hyphens, or braces.
Generate Secure Tokens
Click Generate to create fresh identifiers using your system's hardware-backed random entropy.
Copy Single or Bulk List
Copy individual tokens with one click or export the full batch for database seeds and test fixtures.
UUID Versions Comparison
Overview of RFC 4122 UUID specifications and their primary use cases.
| Version | Generation Basis | Collision Probability | Primary Use Case |
|---|---|---|---|
| Version 1 | MAC address + Timestamp | Very low (reveals MAC address) | Legacy distributed databases |
| Version 4 | Cryptographic pseudo-random numbers | Infinitesimally small (~1 in 10^36) | Primary keys, API tokens, session IDs |
| Version 5 | SHA-1 hash of namespace + name | Deterministic (same input = same UUID) | Deriving consistent IDs from URLs/names |
| Version 7 | Unix timestamp + random entropy | Zero collision with chronological sorting | Time-ordered database primary keys & B-trees |
Frequently Asked Questions
Can two UUID v4 values ever collide?
While theoretically non-zero, generating a collision would require generating billions of UUIDs per second for hundreds of years. In practical software engineering, they are guaranteed unique.
Are these UUIDs cryptographically secure?
Yes. UniTools uses the browser's native `crypto.randomUUID()` API, which draws entropy directly from the operating system CSPRNG.
What is the difference between a UUID and a GUID?
GUID (Globally Unique Identifier) is Microsoft's terminology for a UUID; both conform to RFC 4122 and are functionally identical.
Why do UUIDs contain hyphens?
Hyphens segment the 128-bit value into five hexadecimal groups (8-4-4-4-12) representing time-low, time-mid, time-high-and-version, clock-seq, and node.