UUID/GUID Generator
Generate universally unique identifiers (UUIDs) instantly with our free online tool. Supports UUID v4 (random) and v1 (timestamp-based), bulk generation up to 1000 UUIDs, and custom formatting options including uppercase/lowercase, with/without hyphens, and braces. Perfect for developers, database testing, and any application requiring unique identifiers.
Other Generators
💡 Tip: UUID v4 uses random numbers and is most commonly used. UUID v1 uses timestamps and node information, making it sortable by creation time. Both are guaranteed to be unique!
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Choose UUID Version
Select between UUID v4 (random, most common) or UUID v1 (timestamp-based, sortable by creation time). v4 is recommended for most use cases.Customize Format
Choose your preferred format: uppercase or lowercase, with or without hyphens, and optionally wrap in braces {}. Format updates apply to all generated UUIDs.Select Quantity
Choose how many UUIDs to generate at once: 1, 5, 10, 50, 100, 500, or 1000. Bulk generation is perfect for database seeding and testing.Generate UUIDs
Click the Generate button to create your UUIDs instantly. Each UUID is guaranteed to be unique and follows the standard UUID format.Copy and Use
Copy individual UUIDs or copy all at once (separated by line breaks). Use them in your code, databases, APIs, or any application requiring unique identifiers.
Tips & Tricks
When to Use UUID v4
UUID v4 is the most common type, using random numbers. Use v4 for user IDs, session tokens, API keys, or any scenario where you need unique identifiers without time information. It's the industry standard for most applications.
When to Use UUID v1
UUID v1 includes timestamp information, making UUIDs sortable by creation time. Use v1 for event logging, time-series data, or when you need to track creation order. Note that v1 includes MAC address info (simulated here).
Database Primary Keys
UUIDs make excellent primary keys in distributed databases. They're globally unique, eliminating collision risks when merging data from multiple sources. Use lowercase without braces for most SQL databases.
API Development
Use UUIDs for API request IDs, transaction IDs, and resource identifiers. They're URL-safe (without braces), difficult to guess (enhancing security), and prevent enumeration attacks unlike sequential integers.
Format for Different Languages
JavaScript/Python: lowercase with hyphens. C#/.NET: uppercase with braces {}. Java: lowercase with hyphens. SQL: lowercase without braces. Choose the format that matches your programming language conventions.
Bulk Generation for Testing
Generate 100-1000 UUIDs at once for database seeding, load testing, or creating mock data. Copy all and paste into your seed files, test scripts, or data generation tools.
Collision Probability
UUID v4 collision probability is astronomically low: you'd need to generate 1 billion UUIDs per second for 85 years to have a 50% chance of collision. For practical purposes, UUIDs are always unique.
Storage Considerations
Store UUIDs as binary (16 bytes) in databases for efficiency, not as strings (36-38 characters). Most databases support native UUID types: PostgreSQL has UUID, MySQL has BINARY(16), SQL Server has UNIQUEIDENTIFIER.
Frequently Asked Questions
What is a UUID?
UUID (Universally Unique Identifier) is a 128-bit number used to uniquely identify information in computer systems. Also called GUID (Globally Unique Identifier) in Microsoft systems. UUIDs are standardized by RFC 4122 and OSF (Open Software Foundation).
What's the difference between UUID v1 and v4?
UUID v1 is timestamp-based, using the current time and MAC address (or random node). UUIDs are sortable by creation time. UUID v4 is completely random using cryptographically strong random numbers. v4 is more common and recommended for most use cases due to privacy (no MAC address) and better randomness.
Are UUIDs truly unique?
Yes, for all practical purposes. The probability of generating a duplicate UUID v4 is 1 in 2^122 (5.3 x 10^36). You could generate 1 billion UUIDs per second for 85 years before reaching a 50% chance of collision. No central authority is needed to ensure uniqueness.
Can I use UUIDs as database primary keys?
Yes! UUIDs are excellent for primary keys in distributed systems where multiple databases need to generate IDs independently without coordination. However, they use more storage than integers (16 bytes vs 4-8 bytes) and may be slower for indexing. Trade-offs depend on your use case.
What format should I use for my programming language?
JavaScript/TypeScript/Python: lowercase with hyphens (e.g., '550e8400-e29b-41d4-a716-446655440000'). C#/.NET: uppercase with braces (e.g., '{550E8400-E29B-41D4-A716-446655440000}'). Java: lowercase with hyphens. Choose the format that matches your language conventions.
How do I use bulk-generated UUIDs?
Click 'Copy All' to copy all UUIDs separated by line breaks. Paste into your code, CSV files, database seed files, or test data generators. Each UUID is on its own line, making it easy to import into arrays, databases, or spreadsheets.
Are these UUIDs cryptographically secure?
Our UUID v4 generator uses JavaScript's Math.random(), which is suitable for generating unique identifiers but not cryptographically secure. For security-critical applications (tokens, secrets), use a cryptographically secure UUID library in your backend like Python's uuid module or Node.js crypto.randomUUID().
Can I generate UUIDs offline?
Yes! Once this page loads, all UUID generation happens in your browser using JavaScript. No internet connection is required. Your generated UUIDs are never sent to our servers - everything is processed locally on your device.
What does the hyphen format mean?
Standard UUID format has 5 groups separated by hyphens: 8-4-4-4-12 hex characters (e.g., '550e8400-e29b-41d4-a716-446655440000'). Without hyphens, it's 32 continuous hex characters. Most systems expect hyphens, but some APIs or databases prefer the compact format without hyphens.
How do UUID versions work?
UUID has 5 versions (v1-v5). v1 uses timestamp+MAC address. v2 is DCE Security (rarely used). v3 uses MD5 hashing. v4 uses random numbers (most common). v5 uses SHA-1 hashing. This generator supports v1 and v4, covering 95%+ of use cases.