UUID / GUID Generator
Generate collision-free RFC 4122 Version 4 UUIDs instantly, in bulk, with export options.
Random UUID / GUID Generator: RFC 4122 Version 4 Online Creator & Developer Reference
In modern software engineering, cloud computing, distributed microservices, RESTful APIs, and relational/NoSQL databases, assigning collision-resistant unique keys without central synchronization is critical. Our Random UUID / GUID Generator creates standard 128-bit RFC 4122 Version 4 UUIDs powered by hardware-level cryptographically secure pseudo-random number generators (CSPRNG via crypto.randomUUID() and crypto.getRandomValues()).
Generate single UUIDs on demand or batch export up to 100+ unique identifiers in bulk. Choose from lowercase, UPPERCASE (Windows GUID style), standard 8-4-4-4-12 hyphenated strings, compact 32-character continuous hex without hyphens, curly braces ({...}), and quoted strings for direct array insertion. Press Spacebar for instant generation with zero server telemetry.
CSPRNG Hardware Entropy
Directly utilizes Web Crypto APIs for 122 bits of true entropy, ensuring mathematical collision immunity.
Bulk Batch Generation
Generate 1 to 100+ UUIDs simultaneously for database seed scripts, SQL mock migrations, and test fixtures.
Multi-Format Output
Toggle standard 8-4-4-4-12 hyphens, uppercase/lowercase, Windows GUID braces {GUID}, or clean continuous hex.
100% Client-Side Privacy
Zero network requests, zero telemetry, and zero logging. Your generated identifiers stay strictly inside your browser.
🔬Anatomy of an RFC 4122 Version 4 UUID String
A canonical UUID is represented as 32 hexadecimal digits displayed in 5 groups separated by hyphens (total 36 characters including hyphens):
32 bits of random entropy (time_low field in v1)
16 bits of random entropy (time_mid field)
Starts with 4 (UUID Version 4) + 12 random bits
Starts with 8, 9, a, or b (RFC 4122 variant) + 14 random bits
48 bits of random entropy (node identifier field)
📑UUID Version Comparison & Architectural Specifications
| Version | Generation Mechanism | Primary Use Case | Security & Privacy Properties |
|---|---|---|---|
| UUID v4 (Random) | 122 random bits + 6 version/variant bits | Default for DB keys, API tokens, session IDs | Zero data leakage, maximum entropy |
| UUID v1 (Timestamp) | 60-bit timestamp + MAC network address | Time-ordered legacy distributed nodes | Leaking MAC address & exact creation timestamp |
| UUID v5 (Named SHA-1) | Namespace UUID + string hash (SHA-1) | Deterministic ID generation from URLs / names | Deterministic (same input always produces same UUID) |
| UUID v7 (Time-Ordered) | Unix millisecond timestamp + random bits | B-tree database indexing (PostgreSQL, MySQL) | High locality, chronological index sorting |
💻How to Generate UUID v4 in Modern Programming Languages
const id = crypto.randomUUID();import uuid; id = str(uuid.uuid4())Guid id = Guid.NewGuid();import "github.com/google/uuid"; id := uuid.New().String()SELECT gen_random_uuid();use uuid::Uuid; let id = Uuid::new_v4();❓Frequently Asked Questions
What is the exact mathematical probability of a UUID v4 collision?▾
With 122 bits of pure cryptographic entropy, there are 2^122 (approximately 5.3 × 10^36 or 5.3 undecillion) possible UUID v4 combinations. To have a 50% probability of finding a single duplicate collision, you would need to generate approximately 2.71 quintillion (2.71 × 10^18) UUIDs. Generating 1 billion UUIDs per second for 85 consecutive years yields less than a one-in-a-billion collision chance.
What is the difference between a UUID and a Microsoft GUID?▾
UUID (Universally Unique Identifier) and GUID (Globally Unique Identifier) refer to the exact same 128-bit RFC 4122 / ITU-T standard. Microsoft originally coined "GUID" in COM/ActiveX and commonly writes GUIDs in uppercase with curly braces (e.g. {D3B07384-D113-40B3-8C7C-482A688B1B36}), whereas Unix and open-source ecosystems prefer lowercase "UUID".
What do the 4 and the variant digit signify in the 8-4-4-4-12 structure?▾
In any valid UUID string xxxxxxxx-xxxx-Mxxx-Nxxx-xxxxxxxxxxxx, the M position (the 13th hex character) denotes the UUID version (for v4, it is always 4). The N position (the 17th hex character) encodes the RFC 4122 variant bits (in binary 10xx, corresponding to hex characters 8, 9, a, or b).
Can I use UUID v4 as database primary keys in PostgreSQL, MySQL, and SQLite?▾
Yes! UUID v4 is widely used for primary keys because it allows independent client-side or distributed ID generation without lock contention on centralized auto-increment counters. In high-write workloads where B-Tree index fragmentation is a concern, modern applications also pair UUID v4 with UUID v7 for sequential temporal clustering.
What is a Nil UUID and when is it used?▾
A Nil (null) UUID is a reserved special-case 128-bit identifier where all bits are set to 0 (00000000-0000-0000-0000-000000000000). In software APIs and database foreign keys, it is standardly used as a placeholder to denote an unassigned, empty, or default entity reference.
Are generated UUIDs safe to use in public URLs?▾
Yes. Because UUID v4 contains no personal identifiable information (unlike UUID v1 which leaked MAC addresses and timestamps) and cannot be enumerated sequentially like integer IDs (e.g. /user/101 → /user/102), it protects web applications against Insecure Direct Object Reference (IDOR) scraping attacks.
How does the Spacebar shortcut work in this generator?▾
Pressing the Spacebar key generates a new UUID or batch immediately. You can click on the main UUID display box or the copy button to transfer the value straight to your operating system clipboard.
Is this online UUID generator completely private and safe?▾
Yes, 100%. All UUID generation runs completely client-side in your local browser using the Web Cryptography API. Zero data is transmitted over the internet or saved to server logs, ensuring complete compliance for enterprise and security-sensitive workflows.