Online UUID Generator
Generate random UUIDs (v4) and GUIDs instantly for your applications.
All UUIDs are generated locally in your browser using cryptographically strong random values.
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- UUID v1 (timestamp-based) generation
- UUID v3 and v5 (name-based) with namespaces
- Timestamp decoding from v1 UUIDs
- Bulk generation up to 10,000 UUIDs
- Custom format options (with/without hyphens)
- Export to JSON, CSV, and TXT formats
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About UUID Generator
In modern software development, uniquely identifying entities across distributed systems is a fundamental challenge. UUIDs (Universally Unique Identifiers) solve this problem elegantly by providing 128-bit identifiers that are statistically guaranteed to be unique without requiring central coordination. Our free UUID generator creates RFC 4122 compliant Version 4 UUIDs using cryptographically strong random number generation.
Unlike traditional auto-incrementing database IDs, UUIDs can be generated independently on any device, server, or database and still maintain uniqueness. This makes them perfect for microservices architectures, distributed databases, offline-first applications, and any scenario where you need to create identifiers before synchronizing with a central system. Generate single UUIDs or bulk-create up to 100 at once for batch operations.
Privacy and security are paramount - all UUID generation happens entirely in your browser using the Web Crypto API. Your identifiers never leave your device, and the random values are cryptographically secure, suitable for production use including authentication tokens, session management, and distributed system correlation IDs.
Common Use Cases
Database Primary Keys
Use UUIDs as unique identifiers for database records, ensuring global uniqueness without central coordination.
Distributed Systems
Generate unique identifiers across multiple servers and services without risk of collision or central registry.
API Authentication
Create secure, unpredictable tokens for API keys, session IDs, and authentication credentials.
File Naming
Generate unique filenames for uploads, temporary files, and cache entries to prevent naming conflicts.
Microservices
Track transactions, requests, and events across distributed microservice architectures with unique correlation IDs.
IoT Device IDs
Assign permanent, globally unique identifiers to IoT devices and sensors in large-scale deployments.
Understanding UUID Versions
UUID Version 4 (Random) - Our Implementation
UUID v4 generates identifiers using cryptographically strong random numbers. This is the most common UUID version for general-purpose use. Pros: Completely stateless, no privacy concerns, unpredictable. Cons: Not sortable, slightly larger index size in databases. Best for: API keys, session IDs, general unique identifiers, security tokens.
UUID Version 1 (Time-based)
Generates UUIDs based on timestamp and MAC address. Pros: Sortable by creation time, guaranteed uniqueness within same system. Cons: Exposes hardware MAC address (privacy concern), requires clock synchronization. Best for: Distributed databases where sortability matters, but use with caution in privacy-sensitive applications.
UUID Version 3 & 5 (Name-based)
Creates deterministic UUIDs from namespace and name using hashing (MD5 for v3, SHA-1 for v5). Pros: Same input always generates same UUID, useful for creating reproducible identifiers. Cons: Not random, predictable. Best for: Creating UUIDs from existing identifiers, when you need reproducibility.
Frequently Asked Questions
Technical Specifications
📐 UUID Format Structure
Standard UUID format: xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx
- 36 characters total (32 hexadecimal digits + 4 hyphens)
- Version 4 indicator in position 14 (always '4')
- Variant bits in position 19 (8, 9, A, or B)
- 122 random bits ensuring uniqueness
🔐 Security Characteristics
- Generated using crypto.getRandomValues() (WebCrypto API)
- Cryptographically secure random number source
- Unpredictable - cannot guess future or past UUIDs
- Collision probability: ~1 in 2^122 (effectively zero)
💻 Database Considerations
- Storage: 16 bytes (binary) or 36 bytes (string)
- Indexing: Slightly less efficient than sequential IDs due to randomness
- Recommended: Store as BINARY(16) in MySQL, UUID type in PostgreSQL
- Consider ULID or UUID v7 if you need time-ordered keys
✅ Best Practices
- Use lowercase letters for consistency (though case-insensitive)
- Always include hyphens for standard compliance
- Store in binary format in databases for efficiency
- Don't expose sequential patterns - UUIDs prevent enumeration attacks
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Technical Deconstruction: UUID v4
A Universally Unique Identifier (UUID) is a 128-bit label used for information in computer systems. Karuvii provides an Instant v4 UUID Generator (RFC 4122 compliant), which is the industry standard for random, non-sequential IDs.
Anatomy of v4
xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx
Version 4 UUIDs are easily identifiable. The 13th character (first digit of the third group) is always '4', and the 17th character (first digit of the fourth group) is always '8', '9', 'a', or 'b'.
Collision Probability
The total number of possible v4 UUIDs is 2^122 (approx 5.3 x 10^36). The odds of generating a duplicate are so microscopically small that for all practical database purposes, it is considered zero.
Cryptographic Security (CSPRNG)
Standard random number generators (like Math.random()) are not sufficient for security-critical IDs.
Karuvii uses the Web Crypto API (crypto.getRandomValues()). This accesses the operating system's entropy pool (mouse movements, thermal noise, etc.) to ensure that the generated IDs are truly unpredictable and cryptographically secure.
Why Client-Side Matters?
Privacy is non-negotiable for developers. By generating UUIDs on the client-side:
- Zero Latency: No API calls to wait for.
- Offline Capable: Works without an internet connection.
- Data Sovereignty: The ID is created in your RAM and disappears when you close the tab. No server logs ever record it.
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