Generate random UUID v4 identifiers instantly in your browser. Supports bulk generation, uppercase format, and no-hyphen options — free with no signup.
UUID Generator is a free online tool that creates universally unique identifiers (UUIDs) in multiple versions. UUID v4 uses cryptographically secure random numbers, v1 is timestamp-based, v7 is a modern sortable timestamp format, and ULID provides a compact sortable alternative. Each UUID is a 128-bit value virtually guaranteed to be unique across all systems without requiring central coordination. This tool supports batch generation of up to 100 IDs at once, with options for uppercase formatting, custom separators, and prefix strings.
Use the UUID Generator whenever you need unique identifiers for database records, API resources, session tokens, or distributed system components. UUIDs are especially valuable when you cannot rely on a centralized auto-increment counter — for example, in microservice architectures, offline-first applications, or systems where multiple nodes must independently generate IDs that will never collide. They're also useful for creating temporary filenames, correlation IDs for request tracing, and unique keys for client-side state management.
Software engineers and architects frequently use UUID Generator to create primary keys for database tables in distributed systems, generate unique resource identifiers for REST and GraphQL APIs, produce correlation IDs for tracing requests across microservices, assign unique session or transaction identifiers, create test data with realistic unique IDs during development and QA, and generate idempotency keys for safe API retries. UUIDs are also commonly used as filenames for uploaded assets, as partition keys in NoSQL databases, and as unique identifiers in event-driven architectures and message queues.
Essential terms and definitions related to UUID Generator.
A 128-bit identifier formatted as 32 hexadecimal digits in the pattern 8-4-4-4-12 (e.g., 550e8400-e29b-41d4-a716-446655440000). UUIDs are designed to be globally unique without requiring a central authority. They are widely used as database primary keys, session IDs, and distributed system identifiers.
Microsoft's term for UUID. GUIDs and UUIDs are functionally identical — both are 128-bit identifiers following the same RFC 4122 specification. The term GUID is predominantly used in Microsoft technologies (.NET, SQL Server, COM), while UUID is the platform-neutral term used everywhere else.
Cryptographically Secure Pseudo-Random Number Generator — an algorithm that produces random numbers suitable for security-sensitive operations. Unlike Math.random() which uses a predictable PRNG, CSPRNG (accessed via crypto.getRandomValues in browsers) sources entropy from the operating system and produces output that is computationally infeasible to predict.
Yes. The generator uses the Web Crypto API (crypto.getRandomValues), which provides cryptographically secure random numbers. The probability of generating a duplicate UUID v4 is astronomically low — approximately 1 in 5.3 x 10^36.
UUID v1 is based on the timestamp and MAC address of the generating machine, while UUID v4 is entirely random. This tool generates UUID v4, which is the most commonly used version because it does not leak any information about the generating system.
Yes. The tool offers an option to generate UUIDs without hyphens, producing a 32-character hexadecimal string. This format is useful when UUIDs are used as database keys or in systems that do not accept hyphens.
The bulk generation feature lets you generate multiple UUIDs at once. Since everything runs in your browser, you can generate hundreds of UUIDs instantly without any server requests or rate limits.
Common errors developers encounter and how to resolve them.
UUID v4 collision probability: Risk of duplicate IDs UUID v4 contains 122 bits of random data and can produce a total of 5.3 × 10^36 unique values. To experience a collision, you would need to generate 1 billion UUIDs per second for 100 years — this probability is practically zero. However, if Math.random() is used instead of crypto.getRandomValues(), the PRNG (Pseudo-Random Number Generator) weakness dramatically increases the collision risk. This tool uses CSPRNG (Cryptographically Secure PRNG) to ensure true randomness.
UUID format error: Database says "invalid input syntax for type uuid" The UUID format follows an 8-4-4-4-12 hexadecimal character structure (e.g., 550e8400-e29b-41d4-a716-446655440000). PostgreSQL, MySQL, and other databases strictly adhere to this format. If you are using hyphen-free UUIDs, check whether your database accepts that format. PostgreSQL's uuid type only accepts the hyphenated format. This tool can generate UUIDs in both formats.
UUID sorting issue: Poor database index performance Since UUID v4 is completely random, it can cause page splits and fragmentation in B-tree index structures, which degrades INSERT performance. For high-traffic systems, consider UUID v7 (time-ordered) or ULID (Universally Unique Lexicographically Sortable Identifier) as alternatives — these provide time-based ordering and improve index performance. For standard UUID v4 needs, this tool provides fast and reliable generation.