What is UUID v4?
UUID version 4 is randomly generated. It uses 122 bits of cryptographic randomness, making the probability of generating the same UUID twice effectively zero (1 in 5.3 × 10³¶).
UUID Generator creates cryptographically random UUID v4 identifiers instantly using your browser's built-in secure random number generator. UUIDs (Universally Unique Identifiers) are 128-bit identifiers used as primary keys in PostgreSQL, MySQL, and MongoDB, as object IDs in React and Angular lists, and as idempotency keys in payment systems. Generate as many as you need — each one is statistically guaranteed to be unique.
UUID v4 uses 122 bits of cryptographic randomness from the browser's built-in crypto.getRandomValues() API. The remaining 6 bits are fixed to identify the UUID version and variant. The resulting 128-bit value is formatted as 32 hexadecimal digits in 5 groups separated by hyphens: 8-4-4-4-12 characters.
UUID version 4 is randomly generated. It uses 122 bits of cryptographic randomness, making the probability of generating the same UUID twice effectively zero (1 in 5.3 × 10³¶).
GUID (Globally Unique Identifier) is Microsoft's implementation of UUID. They are functionally identical — the same 128-bit format with the same guarantee of uniqueness. The terms are interchangeable in most contexts.
Yes. UUID v4 is widely used as a primary key in PostgreSQL, MySQL, and MongoDB. Note that random UUIDs can cause index fragmentation — some databases prefer ULID or UUID v7 for sequential insertion performance.
Yes. The tool uses the browser's crypto.getRandomValues() API, which is a CSPRNG (Cryptographically Secure Pseudo-Random Number Generator). Generated UUIDs are suitable for security-sensitive applications.
No. UUID generation runs entirely in your browser. No data is sent to any server.
Yes, completely free. No account or limits.
Tool workspace
Free UUID generator online — instantly generate UUID v4 random identifiers for databases, APIs, distributed systems, and testing. No login, no signup, runs in browser.
Output
Input
Generate UUID v4
Output
550e8400-e29b-41d4-a716-446655440000