What is a UUID?
A UUID (Universally Unique Identifier) is a 128-bit number expressed as 32 hexadecimal digits in 8-4-4-4-12 format, like 550e8400-e29b-41d4-a716-446655440000. They are designed to be unique without coordination — you can generate one on any machine at any time and it will almost certainly never collide with one generated anywhere else. Version 4 UUIDs use 122 bits of cryptographically secure random data, giving roughly 5.3 undecillion (5.3 x 10^36) possible values.
How to use this tool
- 1 Choose how many UUIDs to generate using the Count dropdown — from 1 up to 50.
- 2 Pick a format: Standard (lowercase with hyphens), Uppercase, No hyphens, or GUID braces notation.
- 3 Click Generate to produce a fresh batch, or change Count/Format to auto-regenerate instantly.
- 4 Click the copy icon next to any UUID to copy just that one, or Copy all to grab the entire list as newline-separated text.
Frequently asked questions
Are these UUIDs truly unique?
Version 4 UUIDs have 122 bits of cryptographic randomness generated by crypto.randomUUID(), which uses the operating system's CSPRNG. The probability of a collision between any two v4 UUIDs is astronomically small — roughly 1 in 5.3 undecillion. For practical purposes, treat them as globally unique.
What is the difference between a UUID and a GUID?
Virtually nothing. GUID (Globally Unique Identifier) is Microsoft's name for the same concept. GUIDs are often written in uppercase with curly braces: {550E8400-E29B-41D4-A716-446655440000}. Use the GUID format option to get that notation.
What is UUID v4 vs v7?
v4 is fully random — it has no embedded timestamp. v7 (a newer RFC) encodes a millisecond-precision Unix timestamp in the first 48 bits, making UUIDs sortable by creation time. v7 is preferable as a database primary key because it produces B-tree-friendly monotonically increasing values; v4 causes random page splits.
Is my data sent to a server?
No. All UUIDs are generated using crypto.randomUUID() in your browser. Nothing is transmitted.
Can I use these in a database as a primary key?
Yes, but consider the format. Standard string UUIDs work in any VARCHAR column. For PostgreSQL, use the native UUID type. For MySQL/MariaDB, store as BINARY(16) for better index performance. If insert order matters for performance, prefer v7 UUIDs (sortable) over v4 (random).