Free tool · runs in your browser
UUID Generator
Create random version 4 UUIDs for database keys, request IDs, test fixtures or filenames. Choose how many you need and copy the list.
What version 4 guarantees
A UUID v4 is 128 bits, of which 122 are random; six bits are fixed to mark the version and variant. The result is formatted as five groups of hexadecimal digits. It is not sequential and carries no timestamp, so it reveals nothing about when or where it was created.
Collisions are possible in theory but negligible in practice: you would need on the order of 261 values before a collision becomes likely. For ordinary application IDs, randomness is not the weak point.
v4 versus time-ordered IDs
Random UUIDs make indexes less cache-friendly when used as primary keys, because inserts land at random positions in a B-tree. Time-ordered identifiers such as UUID v7 or ULID keep the uniqueness of a UUID while sorting roughly by creation time, which can improve database write locality.
Pick v4 when order does not matter or unpredictability is useful. Pick a time-ordered scheme when the ID is a high-volume database key.
An identifier is not a secret
UUID v4 is random, but it is designed to be shared in URLs, logs and APIs. It is not an authentication token and should not replace a secret. If an ID grants access to a resource, enforce authorization separately.
Frequently asked questions
Are the generated UUIDs unique?
Uniqueness is probabilistic, not guaranteed. With 122 random bits, the chance of a collision in normal application volumes is astronomically small.
Are they cryptographically random?
Yes. The tool uses crypto.randomUUID when available and otherwise fills 16 bytes with crypto.getRandomValues, then sets the v4 version and variant bits.
Can I use a UUID as a database primary key?
Yes, but random keys can fragment indexes at high insert rates. Consider UUID v7 or ULID if write locality matters.
Do you store the generated values?
No. Generation happens locally and the page keeps nothing after you leave.
How many can I generate at once?
Up to 50 per click. Run it again for more; each click produces new random values.