UUID Generator
Generate RFC 4122 v4 UUIDs in bulk
About this tool
The ToolNinja UUID Generator is a free online UUID and GUID generator. Generate cryptographically random UUID v4 identifiers instantly — individually or in bulk up to 100 at a time. UUIDs (Universally Unique Identifiers) are 128-bit identifiers used as primary keys in databases, unique file names, session tokens, correlation IDs in distributed systems, and anywhere a guaranteed-unique identifier is needed. UUID v4 uses random generation making it ideal for privacy-sensitive use cases where sequential IDs would reveal information about your data volume or timing. Generate a single UUID for quick use, or bulk generate up to 100 UUIDs for seeding test databases, creating fixture data, or batch processing. Copy individually or copy all at once. Each UUID follows the standard 8-4-4-4-12 format (xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx). 100% browser-based using the Web Crypto API for true cryptographic randomness. No login, no server calls required.
When to use it
- →Primary keys for database records in distributed or multi-writer systems
- →Correlation IDs for tracing requests across microservices and logs
- →File names for user-uploaded assets to prevent naming collisions
- →Idempotency keys for payment APIs and write-once operations
Tips
- ◆The format is 8-4-4-4-12 hex digits: xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx. The 4 indicates version 4, and the y is one of 8, 9, a, or b.
- ◆For database primary keys, UUIDs have higher storage overhead than auto-increment integers but work safely in distributed systems without a central coordinator.
Frequently asked questions
Can two generated UUIDs ever be the same?
Theoretically yes, but practically no. The probability of a collision between two random v4 UUIDs is 1 in 2^122 (about 5x10^36). To have a 50% chance of a collision, you'd need to generate 2.7x10^18 UUIDs — far beyond any realistic system.
What's the difference between UUID v1, v4, and v7?
V1 is time-based and includes the machine's MAC address — deterministic but leaks information. V4 is fully random — the most widely used version. V7 is a newer standard that's time-ordered (sortable) while remaining random enough to be collision-safe — better for database index performance.
Should I use UUID or auto-increment integers for database IDs?
Auto-increment integers are simpler and more storage-efficient. UUIDs are better when you need IDs generated client-side before writing to the database, when merging records from multiple sources, or when you don't want sequential IDs that expose record counts.
Is GUID the same as UUID?
Yes. GUID (Globally Unique Identifier) is Microsoft's term for the same concept. A GUID and a UUID v4 are interchangeable in most contexts, though GUIDs are sometimes written without hyphens and may use uppercase hex digits.