Generate UUID v4 identifiers. Single or bulk generation, validate UUIDs, copy with one click. All processing happens in your browser.
Click Generate to create a UUIDPaste a string to check if it is a valid UUID v4
UUID (Universally Unique Identifier) v4 uses random numbers and provides 122 bits of randomness. Ideal for unique IDs, correlation IDs, and non-guessable tokens.
Need API Development?A UUID (Universally Unique Identifier) is a 128-bit identifier represented as 32 hexadecimal characters, often with hyphens: 8-4-4-4-12. UUID v4 uses random numbers, providing 122 bits of randomness and making collisions astronomically unlikely in practice.
UUIDs are used for primary keys in databases, correlation IDs in distributed systems, session tokens, file identifiers, and non-guessable URLs. They can be generated offline without coordination, unlike sequential IDs.
The version digit (4) and variant bits are fixed. The rest is random. Hyphens are optional; both 550e8400-e29b-41d4-a716-446655440000 and550e8400e29b41d4a716446655440000 are valid representations.
a-f) and uppercase (A-F) hex characters.The UUID specification defines several versions, each with a different generation strategy. Version 1 uses the current timestamp and the machine's MAC address, making it sortable but potentially leaking hardware identity. Version 4 (generated by this tool) relies entirely on random numbers, providing strong uniqueness without revealing any system information. Version 5 creates deterministic UUIDs by hashing a namespace and name with SHA-1, useful when you need the same input to always produce the same UUID.
Auto-incrementing integers are simple and storage-efficient but expose record counts, create merge conflicts in distributed systems, and require a central authority. UUIDs can be generated independently on any node without coordination, making them ideal for microservices, offline-first apps, and systems that merge data from multiple sources. The trade-off is larger storage size (16 bytes vs 4-8 bytes) and less cache-friendly index patterns in some databases.
Theoretically yes, but the probability is vanishingly small. With 122 random bits, you would need to generate approximately 2.71 quintillion UUIDs to have a 50% chance of a single collision. In practice, UUID v4 collisions do not happen.
UUID v4 values are random and non-sequential, so they do not reveal record counts or creation order. However, UUIDs alone should not be treated as an access control mechanism—always pair them with proper authentication and authorization.
Storing as a 16-byte binary field (e.g., BINARY(16) in MySQL or uuid type in PostgreSQL) is more storage-efficient and faster for indexing. If your ORM or application layer works more easily with strings, the overhead of a 36-character VARCHAR is usually acceptable for moderate-scale systems.