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UUID & ULID Generator

Random UUIDs (v4, v7) and ULIDs.

Free tools that run in your browser. Nothing you type, open or create is uploaded to NerdBible or anyone else.


  
Read the time inside a UUID v7 or ULID

  
  
  
The creation time is shown here.




Every ID is made in your browser with the Web Crypto random number generator. UUID v4 uses crypto.randomUUID where available. UUID v7 and ULID put the current time in milliseconds first, so they sort by creation time; IDs made in the same millisecond still sort in the order they were made.



  
How to use it

  
  1. Pick the type: UUID v4, UUID v7, ULID or NanoID.
  2. Set how many you need, up to 1,000, and the format options.
  3. Copy them all or download them as a text file.





  
Questions

  
Which one should I use?
UUID v4 is the safe default when you only need a unique ID. Use UUID v7 or ULID for database keys, because they sort by time and keep indexes compact. NanoID is shorter and URL friendly, good for public IDs in links.
Can two UUIDs ever be the same?
In practice, no. A v4 UUID has 122 random bits; you would need to make billions every second for many years before a repeat became likely.
Does a UUID v7 reveal anything?
It reveals when it was created, to the millisecond, as the reader below shows. If creation times are sensitive, use v4 instead.
What is the difference between a UUID v7 and a ULID?
Both start with a 48 bit timestamp followed by random bits. A UUID v7 is written as 36 hex characters with hyphens and fits UUID columns; a ULID is 26 characters of Crockford Base32, shorter and case insensitive.




      
      

    
About this tool

    
About the UUID generator
Unique IDs let systems create records without asking a central database for the next number. This tool generates four popular kinds, up to 1,000 at a time, to copy or download as a text file.
Which one to use
  • UUID v4: 122 random bits. The safe default when you just need a unique ID.
  • UUID v7: starts with the current time in milliseconds, then random bits, so IDs sort by creation time. Good for database primary keys, because new rows land at the end of the index.
  • ULID: the same time-then-random idea written as 26 characters of Crockford Base32, shorter than a UUID and case insensitive.
  • NanoID: short, URL-friendly random IDs, good for public links.
IDs made in the same millisecond still sort in the order they were made.
Can two ever collide?
In practice, no. You would need to generate billions of v4 UUIDs every second for many years before a repeat became likely.
A privacy note on v7
A UUID v7 or ULID reveals when it was created, to the millisecond, and the reader on the page shows it. Use v4 where creation times are sensitive.
Every ID is generated with your browser's cryptographic random number generator and never sent anywhere.
  

        

    
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