UUID Generator
Generate UUID v1 and v4 instantly. Choose the version, how many you need (up to 1000), uppercase, and whether you prefer the version without hyphens.
Settings
Result (0 UUIDs · V4)
How to use: UUID
- 1Pick the version: v4 (random) or v1 (time-based).
- 2Choose how many UUIDs you need (up to 1,000) and the format.
- 3Generate and copy the list, one per line or comma-separated.
What is it for?
- Create unique identifiers for database records.
- Generate test data and fixtures.
- Get IDs for files, sessions or events.
UUIDs: versions and good practice
What a UUID is
A UUID is a 128-bit identifier written as 32 hexadecimal digits in 8-4-4-4-12 groups. It is designed to be generated independently on any machine without coordinating with a central server, and in practice never to repeat.
v1, v4 and v7
Version 4 is random (122 random bits) and is the most widely used. Version 1 combines a timestamp with node data, so it can reveal when and where it was created. Version 7, the newest, starts with a millisecond timestamp and sorts chronologically, which greatly improves database index performance compared to v4.
Can collisions happen?
With UUID v4 you would need to generate about 2.7 quintillion (2.7 × 10^18) identifiers to have a 50 % chance of a single collision. In practice, failures come from badly seeded random generators, not from the size of the space. This tool uses the browser's cryptographic generator (crypto.randomUUID).
Database tips
Store the UUID in a native type (uuid in PostgreSQL, BINARY(16) in MySQL) rather than text: it takes 16 bytes instead of 36 and compares faster. If the table is very large and heavily inserted into, consider UUID v7 or another sortable identifier to avoid index fragmentation.
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Frequently asked questions
What's the difference between v1 and v4?+
v4 uses random values (recommended). v1 includes a timestamp and MAC address, so it's predictable and best avoided for security.