generation
UUID Generator
Generate one or more cryptographically random UUID v4 identifiers instantly.
What is UUID Generator?
A UUID (Universally Unique Identifier) is a 128-bit identifier standardised in RFC 4122 and represented as 32 hexadecimal digits in the pattern xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx. UUID version 4 — the most common variant — fills all bits with cryptographically random data, making collisions statistically impossible: with 1 trillion UUIDs generated per second it would take approximately 85 years before a 50% chance of a single collision occurs. UUIDs are used as primary keys in databases, correlation IDs in distributed logs, session tokens, file names, API resource identifiers, and idempotency keys in payment systems. Because they are generated client-side without a central registry, distributed systems can create UUIDs in parallel without coordination. The compact format (no hyphens) saves 4 characters and is commonly used in URLs and file names.
How to use UUID Generator
- Choose how many UUIDs you need: Set the count to 1 for a single identifier or up to 100 for a bulk batch — useful when pre-generating IDs for a database seed script or test fixture.
- Choose a format: Hyphenated format (xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx) is the RFC 4122 standard and is accepted by most databases and ORMs. Compact format (no hyphens, 32 hex chars) is smaller and safe for URLs, file names, and systems that require alphanumeric-only keys.
- Copy and use: Click Copy to put all generated UUIDs on your clipboard — one per line for multi-UUID batches. To validate an existing UUID, paste it into the 'validate' field and the tool reports whether it matches the UUID format and which version it is.
Frequently asked questions
- Are UUID v4 values truly random and safe to use as primary keys?
- Yes. UUID v4 uses a cryptographically secure random number generator (Node.js crypto.randomUUID(), which calls the OS CSPRNG). Two independently generated v4 UUIDs colliding is astronomically unlikely — roughly a 1 in 5.3×10³⁶ chance per pair. They are safe as primary keys in databases, session tokens, and correlation IDs.
- What is the difference between UUID v1, v4, and v7?
- v1 encodes the MAC address and timestamp — sortable but exposes hardware identity. v4 is fully random — the most privacy-safe and widely supported. v7 (RFC 9562, 2024) encodes a millisecond-precision timestamp in the high bits so UUIDs sort chronologically, which improves database index locality. This tool generates v4. For v7, use a dedicated library like 'uuid' on npm.
- Can I use a UUID without the hyphens?
- Yes. Hyphens are part of the canonical textual representation but carry no information — the 128-bit value is identical. The compact format (32 hex chars, no hyphens) is common in URLs, file names, and storage systems that require alphanumeric-only identifiers. Most UUID parsers accept both formats.
- How does UUID v4 compare to ULID or NanoID?
- UUID v4 is the most widely supported format — accepted by PostgreSQL, MySQL, MongoDB, and virtually every ORM. ULID encodes a millisecond timestamp in the first 48 bits, making it lexicographically sortable (useful for database index locality), and uses Crockford's Base32 encoding for a shorter string. NanoID is smaller (21 chars by default) and URL-safe, but is not a UUID and requires a library. Use UUID v4 for maximum compatibility, ULID or UUID v7 when insertion-order sortability matters.
- Are UUIDs case-sensitive?
- UUID values are hexadecimal and case-insensitive — '550e8400-E29B-41D4-A716-446655440000' and '550e8400-e29b-41d4-a716-446655440000' represent the same value. RFC 4122 recommends lowercase output, which is what most libraries and databases produce. When comparing UUIDs, always normalize to the same case.
- Can two independently generated UUID v4s ever collide?
- In practice, no. UUID v4 has 122 random bits (the other 6 bits are fixed for version and variant). The probability of any two UUIDs colliding is approximately 1 in 5.3 × 10³⁶. If you generated 1 billion UUIDs per second for 100 years, the probability of even a single collision would be astronomically small. Collisions happen in practice only when a broken random number generator produces repeated output.