UUID Generator: Complete Guide to Creating & Validating Universally Unique Identifiers
Universally Unique Identifiers (UUIDs) are 128-bit numbers used to uniquely identify information in computer systems without central coordination. Our free UUID generator provides instant UUID generation with support for UUID v1 (timestamp-based), UUID v4 (random), and UUID v5 (namespace-based), multiple UUID generation, uppercase/lowercase formatting, with/without hyphens, UUID validation, and GUID format support. Whether you're developing databases, building APIs, creating distributed systems, or generating unique identifiers for records, this tool delivers cryptographically strong UUIDs entirely in your browser.
What is a UUID?
A UUID (Universally Unique Identifier) is a 128-bit label used for information in computer systems. UUIDs are standardized by the Open Software Foundation (OSF) as part of the Distributed Computing Environment (DCE). The formal definition is in RFC 4122. A UUID is displayed as 32 hexadecimal digits in five groups separated by hyphens: 8-4-4-4-12, for example: 550e8400-e29b-41d4-a716-446655440000. UUIDs are designed to be unique across space and time without requiring a central registration authority.
Why Use UUIDs?
1. Database Primary Keys
Developers use UUIDs as primary keys in databases instead of auto-incrementing integers. UUIDs allow distributed systems to generate keys independently without coordination, prevent ID collision when merging databases, hide the number of records from competitors (auto-increment reveals count), and enable offline record creation before syncing to servers. They're essential for distributed databases, microservices, and multi-tenant applications.
2. API and Web Development
Web developers use UUIDs for session IDs, API keys, request tracking, temporary file names, and resource identifiers. UUIDs in URLs prevent enumeration attacks (guessing sequential IDs), make URLs unpredictable for security, and work well in RESTful API design. They're commonly used in authentication tokens, OAuth2 implementations, and distributed tracing systems.
3. Distributed Systems and Microservices
Distributed systems generate UUIDs for message IDs, transaction IDs, correlation IDs for logging, event IDs in event-driven architectures, and node identifiers. UUIDs allow each service to generate identifiers independently without centralized coordination, which is critical for scalability, fault tolerance, and avoiding single points of failure.
4. File and Resource Management
Systems use UUIDs for file names (preventing overwrites), temporary file identifiers, cloud storage object keys, cache keys, and job queue identifiers. UUIDs ensure no naming conflicts when multiple users or processes create files simultaneously, making them ideal for cloud storage, content delivery networks, and distributed file systems.
For working with other unique identifiers, check our hash generator tool.
UUID Versions Explained
UUID v1 (Timestamp-based)
UUID v1 generates identifiers based on the current timestamp and the MAC address of the computer generating the UUID. The timestamp ensures uniqueness over time, and the MAC address ensures uniqueness across machines. Version 1 UUIDs can reveal when and where they were generated, which can be a security concern. They're useful when you need chronologically sortable UUIDs or when timestamp information is valuable for debugging. Example: 550e8400-e29b-41d4-a716-446655440000
UUID v4 (Random)
UUID v4 is the most commonly used version. It generates completely random UUIDs using cryptographically strong random number generators. Version 4 UUIDs have 122 bits of randomness (6 bits are used for version and variant), providing extremely low collision probability (1 in 2^122). They're ideal for most applications because they're unpredictable, don't reveal information about generation time or location, and are simple to generate. Example: 7c9e6679-7425-40de-944b-e07fc1f90ae7
UUID v5 (Namespace-based with SHA-1)
UUID v5 generates deterministic UUIDs based on a namespace identifier and a name. It uses SHA-1 hashing to convert the namespace + name into a UUID. Given the same namespace and name, v5 always produces the same UUID, making it perfect for generating consistent identifiers from existing data like domain names, URLs, or object identifiers. Predefined namespaces include DNS (for domain names) and URL (for web addresses). Example: generate UUID v5 for namespace DNS and name "example.com" always produces the same UUID.
Key Features of Our UUID Generator
1. Multiple UUID Versions
Generate the exact UUID type you need:
- UUID v1: Timestamp-based identifiers with MAC address
- UUID v4: Purely random UUIDs (most common)
- UUID v5: Namespace-based deterministic UUIDs using SHA-1
2. Bulk Generation
Generate multiple UUIDs at once - up to 100 in the free version. Perfect for seeding databases, creating test data, generating batch identifiers, or populating development environments. Premium users can generate up to 1000 UUIDs at once for enterprise-scale needs.
3. Flexible Formatting
Customize UUID format to match your requirements:
- Uppercase/Lowercase: Choose between lowercase (550e8400...) or uppercase (550E8400...)
- With/Without Hyphens: Standard format (550e8400-e29b-41d4-a716-446655440000) or compact (550e8400e29b41d4a716446655440000)
4. UUID Validation
Validate existing UUIDs to ensure they're properly formatted and identify which version they are. The validator checks format compliance, detects UUID version (v1, v4, v5, etc.), verifies variant bits, and accepts both hyphenated and non-hyphenated formats. This helps verify UUIDs from external sources, debug UUID-related issues, and ensure data quality.
5. Namespace Support (UUID v5)
Use predefined namespaces (DNS for domain names, URL for web addresses) or custom namespaces (Premium) for UUID v5 generation. Enter a name value to generate deterministic UUIDs that remain consistent for the same input. Perfect for converting existing identifiers (domain names, URLs, email addresses) into UUIDs.
6. GUID Format Support
GUIDs (Globally Unique Identifiers) are Microsoft's implementation of UUIDs and use the exact same format. Our generator creates UUIDs that are fully compatible with GUID requirements in .NET, Windows development, and Microsoft systems. The terms are often used interchangeably.
How to Use the UUID Generator
- Select UUID Version: Choose v1 (timestamp), v4 (random), or v5 (namespace)
- Configure v5 Options (if applicable):
- Select namespace (DNS, URL, or Custom with Premium)
- Enter name value (e.g., domain name or URL)
- Set Count: Specify how many UUIDs to generate (1-100 free, up to 1000 with Premium)
- Choose Format: Enable/disable uppercase and hyphens
- Generate UUIDs: Click "Generate UUIDs" to create identifiers
- Copy or Download: Copy individual UUIDs, copy all, or download as a text file
- Validate UUIDs (optional): Enter any UUID in the validator to check format and version
Common Use Cases
Database Primary Keys
Use UUID v4 as primary keys in PostgreSQL, MySQL, MongoDB, and other databases. UUIDs prevent ID collision in distributed databases, allow offline record creation before syncing, hide record counts from competitors, and enable easy database merging. They're essential for multi-tenant SaaS applications, microservices architectures, and distributed systems where multiple services create records independently.
RESTful API Development
Use UUIDs in REST API URLs (e.g., /api/users/550e8400-e29b-41d4-a716-446655440000) to prevent enumeration attacks, make resource IDs unpredictable, avoid exposing business metrics through sequential IDs, and create stateless, cacheable APIs. UUIDs work perfectly with HTTP methods (GET, POST, PUT, DELETE) and follow RESTful best practices.
Session and Token Management
Generate session IDs, authentication tokens, password reset tokens, email verification tokens, and API keys using UUID v4. The randomness ensures tokens are unpredictable and secure. UUIDs are commonly used in OAuth2 flows, JWT token identifiers, and session management systems for web applications.
Distributed Tracing and Logging
Use UUIDs for correlation IDs, request IDs, trace IDs in distributed systems, transaction IDs, and log entry identifiers. This allows tracking requests across multiple services, correlating logs from different systems, debugging distributed transactions, and implementing observability tools like Jaeger, Zipkin, or AWS X-Ray.
File and Asset Management
Generate unique file names for uploads, temporary files, cache keys, CDN asset identifiers, and cloud storage object keys. UUIDs prevent file name conflicts when multiple users upload files simultaneously, enable safe parallel processing, and work well with cloud services like AWS S3, Google Cloud Storage, and Azure Blob Storage.
UUID Format and Structure
Standard Format
The canonical UUID format is: xxxxxxxx-xxxx-Mxxx-Nxxx-xxxxxxxxxxxx, where x is a hexadecimal digit (0-9, a-f), M is the UUID version (1, 4, 5, etc.), and N is the variant (8, 9, a, or b in RFC 4122). Example: 550e8400-e29b-41d4-a716-446655440000. This breaks down as: 8 hex digits - 4 hex digits - 4 hex digits - 4 hex digits - 12 hex digits.
Version and Variant Bits
The 13th hex digit (M position) indicates the UUID version: 1 for v1, 4 for v4, 5 for v5, etc. The 17th hex digit (N position) indicates the variant: values 8, 9, a, or b indicate RFC 4122 compliance. These bits ensure UUIDs can be identified and parsed correctly across different systems and implementations.
UUID Collision Probability
How Likely Are Collisions?
For UUID v4, with 122 bits of randomness, the probability of collision is astronomically low. To have a 50% chance of collision, you'd need to generate 2.71 quintillion (2.71 × 10^18) UUIDs. For practical purposes, generating 1 billion UUIDs per second for 100 years yields less than 0.00000006% chance of collision. This makes UUID v4 safe for virtually all applications without central coordination.
When to Worry About Collisions
UUID collisions are a theoretical concern, not a practical one for most applications. You should only worry if using a weak random number generator, generating trillions of UUIDs, or deliberately trying to create collisions. Always use cryptographically strong random generators (like crypto.getRandomValues() in browsers or /dev/urandom on Linux) for production systems.
UUIDs vs Other Identifiers
UUIDs vs Auto-Increment IDs
UUIDs Pros: No coordination needed, work in distributed systems, unpredictable, hide record counts, allow offline creation
UUIDs Cons: Larger storage (16 bytes vs 4-8 bytes), not sequential, slower indexing in some databases
Auto-Increment Pros: Smaller, sequential, simpler, better for some database indexes
Auto-Increment Cons: Require central coordination, expose record counts, problematic in distributed systems
UUIDs vs Hashes
Hashes (MD5, SHA-256) are deterministic - same input produces same output. UUIDs (v1, v4) are unique regardless of input. Use hashes for data integrity and checksums. Use UUIDs for unique identifiers. UUID v5 combines both approaches - it's a deterministic UUID based on hashing namespace + name.
Related Tools for Developers
Enhance your development workflow with complementary tools. For generating hashes, use our hash generator. For password generation, try our password generator. For encoding data, check our Base64 encoder.
Why Choose Our UUID Generator?
- 100% Free: Core features available without payment
- Three UUID Versions: v1 (timestamp), v4 (random), v5 (namespace)
- Bulk Generation: Generate up to 100 UUIDs at once (1000 with Premium)
- Flexible Formatting: Uppercase/lowercase and with/without hyphens
- UUID Validation: Verify format and identify version
- Namespace Support: DNS and URL namespaces for UUID v5
- GUID Compatible: Works with Microsoft GUID requirements
- Copy & Download: Copy individual, copy all, or download as file
- Privacy-First: All generation in your browser - no server involved
- Cryptographically Strong: Uses secure random number generation
Frequently Asked Questions
Which UUID version should I use?
For most applications, use UUID v4 (random). It's simple, secure, and unpredictable. Use v1 if you need timestamps or chronological sorting. Use v5 if you need deterministic UUIDs (same input always produces same UUID), such as converting existing identifiers to UUID format.
What's the difference between UUID and GUID?
They're essentially the same thing. UUID is the standardized term (RFC 4122), while GUID is Microsoft's name for the same concept. The format and structure are identical. You can use our generator for both UUID and GUID needs.
Can two UUIDs ever be the same?
Theoretically yes, but the probability is so low it's negligible. For UUID v4, you'd need to generate quintillions of UUIDs to have a meaningful chance of collision. In practice, UUID collisions are not a concern if you use proper random number generators.
Should I use UUIDs with or without hyphens?
With hyphens is the standard format and more readable (550e8400-e29b-41d4-a716-446655440000). Without hyphens is more compact (550e8400e29b41d4a716446655440000). Most systems accept both, but hyphenated is preferred for human readability. Databases like PostgreSQL have native UUID types that handle both.
Are the UUIDs generated securely?
Yes! Our generator uses the browser's crypto.getRandomValues() function, which provides cryptographically strong random numbers suitable for security-sensitive applications. All generation happens locally in your browser - UUIDs are never sent to any server.
Conclusion
Our free UUID generator provides professional-grade unique identifiers with support for UUID v1, v4, and v5, bulk generation, flexible formatting, validation, and namespace support. Whether you're building databases, developing APIs, implementing distributed systems, managing sessions, or creating unique file names, this tool delivers cryptographically strong UUIDs instantly.
With GUID compatibility, uppercase/lowercase options, hyphen control, and browser-based generation for complete privacy, it's the perfect tool for developers, database administrators, and system architects. Start generating UUIDs now and bring unique identification to your applications!