What is a UUID v4 and what is the probability of a duplicate collision?

A UUID v4 is a 128-bit identifier with 122 bits of random entropy (3.4 × 10³⁸ possible combinations). The probability of generating a duplicate UUID v4 is so infinitesimally small (roughly 1 in a billion billion) that collisions are practically impossible in software development.

How does a UUID contrast with a Microsoft GUID?

UUID (Universally Unique Identifier) is the standard IETF term, while GUID (Globally Unique Identifier) is Microsoft's terminology for the exact same 128-bit RFC 4122 specification.

What does the 8-4-4-4-12 hexadecimal structure represent?

The 36-character string (e.g. `123e4567-e89b-12d3-a456-426614174000`) encodes 32 hexadecimal digits separated by 4 hyphens, with specific positions reserved for version (e.g. `4`) and variant.

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UUID / GUID Generator & Inspection Studio

Generate cryptographically secure Universal Unique Identifiers (UUID / GUID) with our UUID Generator & Inspector! Powered by standard `crypto.getRandomValues()` entropy, our tool generates bulk UUID v4 (random), UUID v1 (time-based), uppercase/lowercase strings, braces, hyphens, and custom batch exports for database keys.

✨ NLP PROMPT ENGINEType your generation or validation query in plain English (e.g. "Create 15 v1 UUIDs")

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Or try prompts:

32-Digit Hex Engine (RFC 4122 Compliant)

V4Random High Entropy

V1Date-time / MAC

V5SHA-1 Deterministic

V3MD5 Deterministic

Bulk ID Generation Counter

Formatting Toggles

UPPERHyphens{}

Output Syntax

🎯 Result

8925db6c-274e-4068-b4da-a66cb56a6d65

📖 UUID Version Guide: When to use which?

v1Time-based

Logic: Date-time and MAC address

Primary Use: Time-ordered sequences

v2DCE Security

Logic: Date-time and POSIX UID/GID

Primary Use: Legacy system security

v3Deterministic

Logic: Namespace and name (MD5)

Primary Use: Repeatable IDs (Fast)

v4Randomness

Logic: Random high-entropy number

Primary Use: Default / General IDs

v5Deterministic

Logic: Namespace and name (SHA-1)

Primary Use: Repeatable IDs (Secure)

📊 Deterministic Namespace References (V3 & V5 Combinations)

Version	Namespace Type	Name Input String	Deterministic UUID Output (Copyable)
V3	DNS	example.com	9073926b-929f-31c2-abc9-fad77ae3e8eb
V5	DNS	example.com	cfbff0d1-9375-5685-968c-48ce8b15ae17
V3	DNS	nextools-tool	cd4802b9-3f6a-322c-8884-f12e205892c4
V5	DNS	nextools-tool	ec90bdfe-6389-5dfc-b36e-377b1f3205a2
V3	URL	example.com	a0473a67-27a1-3c05-a2d1-5c134639347f
V5	URL	example.com	a5cf6e8e-4cfa-5f31-a804-6de6d1245e26
V3	URL	nextools-tool	c019e5df-ac11-3e99-82c1-96cf6fddebde
V5	URL	nextools-tool	97508cb3-dbf4-5991-9ca8-79c6712134f6
V3	OID	example.com	109f8204-164d-33ef-871d-d92c373e8c66
V5	OID	example.com	eb6106fd-8a37-5395-b3f7-7cb93195fdba
V3	OID	nextools-tool	a60de2fb-44e0-3ee5-986f-6acff1d867c7
V5	OID	nextools-tool	3fc4c444-4034-5d19-b215-eb0ea2207374
V3	X500	example.com	11c2f001-e3a4-3ad0-90f7-88ac418c36b8
V5	X500	example.com	f014ed3c-177a-541e-a840-fc330670f8e8
V3	X500	nextools-tool	284af703-9be2-3cb1-b522-e3bf57517a49

🛠️ UUID Version 4 vs. Version 1: Architecture & Collisions

Universally Unique Identifiers (UUIDs), standardized under RFC 4122 and ISO/IEC 9834-8, are 128-bit identifiers designed to provide guaranteed uniqueness across distributed systems without central coordination authorities.

UUID Version 4 (Random / Pseudo-Random)

Version 4 relies on 122 bits of unpredictable cryptographic entropy (with 6 bits reserved for version and variant metadata). It avoids leaking machine MAC addresses or timestamp information, making it the industry standard for database primary keys, session tokens, and microservices.

UUID Version 1 (Time-Based + MAC)

Version 1 encodes a 60-bit timestamp (measured in 100-nanosecond intervals since the Gregorian calendar reform) combined with the physical network card MAC address. While sequential, it exposes machine identity and creation time.

⚡ Generating RFC 4122 UUIDs Across Programming Stacks

Language	Native Method / Package	Command
JavaScript / Node	Web Crypto / crypto module	`crypto.randomUUID()`
Python	Standard library `uuid`	`import uuid; uuid.uuid4()`
Go	`github.com/google/uuid`	`uuid.New().String()`
Bash / cURL	Linux `uuidgen` / procfs	`uuidgen -r`

❓ Frequently Asked Questions — UUID Generator

What is the probability of a UUID v4 collision?

With 2¹²² (≈ 5.3 × 10³⁶) possible values, you would need to generate 1 billion UUIDs every second for approximately 100 years before having a 50% probability of a single collision.

Why does NexTools use Web Crypto instead of Math.random()?

Standard Math.random() uses linear PRNG algorithms that are predictable and exhibit state cycles. NexTools strictly employs window.crypto.getRandomValues, drawing entropy directly from the OS kernel CSPRNG.

Are generated UUIDs transmitted over the network?

No. Generation occurs 100% in your local browser memory. You can disconnect your network and batch generate 500 UUIDs completely offline.

Can I generate Nil (empty) or namespace UUIDs?

Yes. The studio supports Nil UUIDs (all zeros), UUID v1 (timestamp), UUID v3 (MD5 namespace), and UUID v5 (SHA-1 namespace) for deterministic hashing.