UUID generator
Generate random version 4 UUIDs on your device, with batch count, hyphen, uppercase, copy, and download controls.
How it works & useful details
How to use this tool
Choose a count and format, then generate fresh UUIDs. Copy or download the newline-separated output.
Details and limits
Version 4 UUIDs use 122 random bits from Web Crypto; the version and variant bits are set explicitly. Generate 1–100 at a time. Hyphen-free output is a compact representation of the same identifier.
Nothing is generated on page load. UUIDs are identifiers, not a claim of guaranteed uniqueness or authentication credentials.
About this tool
UUID generator creates random version 4 UUIDs on your device, with controls for batch size, hyphenation, and uppercase formatting. It is useful for database keys, correlation IDs, and test data.
Because the values come from your browser’s cryptographic random source, they are suitable for identifiers that must not collide or be guessable. Nothing is sent to a server.
How to use it
- Set how many UUIDs you need.
- Choose whether to keep hyphens and use uppercase.
- Generate the batch.
- Copy a single value or download the list.
Anatomy of a version 4 UUID
a62d96fc-0abf-4852-9d2c-2c8315565a7c
^ ^
| variant (8, 9, a, or b)
version (always 4)A UUID is 128 bits written as 32 hex digits in groups of 8-4-4-4-12. In version 4, six bits are fixed to mark the version and variant, and the other 122 bits are random. The first digit of the third group is always 4, and the first digit of the fourth group is always 8, 9, a, or b.
How unique is unique?
With 122 random bits there are about 5.3 × 10³⁶ possible values. You would need to generate roughly 2.7 × 10¹⁸ UUIDs, a billion per second for 85 years, before the chance of a single duplicate reaches 50%. In practice, collisions come from broken random number generators, not from the math. This tool uses the browser's cryptographic generator.
Random UUIDs make good primary keys when records are created on many machines, as well as idempotency keys, file names, and correlation IDs. They are not ordered. Databases that index them may benefit from time-ordered alternatives like UUID version 7. They are also not secrets: never use a UUID as an access token or password-reset code, even though it is hard to guess.
Frequently asked questions
What kind of UUID is generated?
Version 4 random UUIDs, which contain no timestamp or machine information.
Are UUIDs guaranteed to be unique?
Random v4 UUIDs have 122 random bits, so collisions are astronomically unlikely, but not mathematically impossible.
Can I generate UUIDs without hyphens?
Yes. Hyphenation is a display choice; both forms represent the same 128-bit value.
Are uppercase or hyphen-free UUIDs still valid?
They represent the same 128-bit value. RFC 9562 recommends lowercase with hyphens for output, but most parsers accept either case. Some systems, such as Windows GUID tools, display them in uppercase.