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UUID Generator (Version 4)

Generate random version 4 UUIDs in your browser, and check whether a pasted UUID is valid.

UUID generator
Choose how many and press Generate.

Result
UUIDs
Paste a UUID above to check it
Check result
Private: Everything runs in this page. Nothing you type is sent anywhere or saved.
Updated 
On this page
  1. How the format is built
  2. Formula
  3. How the uuid generator works
  4. What this tool does not do
  5. Frequently asked questions
  6. References
  7. Related tools
How the format is built
Random bytesUUID
all zero bytes00000000-0000-4000-8000-000000000000
bytes 0 to 1500010203-0405-4607-8809-0a0b0c0d0e0f
all 255 bytesffffffff-ffff-4fff-bfff-ffffffffffff
Formula
xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx where 4 is the version and y is 8, 9, a or b
How the uuid generator works
  1. Step oneChoose how many UUIDs you want and any format options, then press Generate.
  2. Step twoEach UUID is 16 random bytes with the version (4) and variant bits set, written as 8-4-4-4-12 hex digits.
  3. Step threeCopy the list. Paste any UUID into the check box to see its version.
What this tool does not do
  • It makes random version 4 UUIDs only; there are no time-based or name-based ones.
  • A UUID is not a secret: do not use one as a password or an access token.
  • It does not check that an ID is unused in your system.
Frequently asked questions
Can two UUIDs be the same?
With 122 random bits per version 4 UUID, an accidental repeat is not a practical concern.
What does version 4 mean?
The UUID is built from random numbers only, with no clock or machine address inside.
Are the UUIDs kept anywhere?
No. They are made in your browser and not stored or sent.
References