UUID Generator
Choose how many version 4 UUIDs you need, generate them, and copy the list in one click.
Runs in your browser. Nothing you enter is uploaded.
What it does
A UUID (universally unique identifier) is a 128-bit value written as 32 hex characters in the pattern 8-4-4-4-12. This page produces version 4 UUIDs, which are random, using the browser's crypto.randomUUID function where available. Five are ready when the page loads.
Developers use them as primary keys, idempotency keys, correlation IDs in logs, or IDs in JSON fixtures. Generating a batch of up to 50 here saves opening a terminal or writing a throwaway script, and the list copies as one block ready to paste.
How to use it
- 1
Enter a number from 1 to 50 in How many.
- 2
Leave Version on UUID v4 (random), the only option.
- 3
Click Generate UUIDs.
- 4
Click Copy next to Result to copy every UUID, one per line.
What you get
A list of lowercase version 4 UUIDs, one per line, such as 3f1c9a52-7d4e-4b8a-9c21-5e6f0a7b8c9d. The Copy button copies the whole list.
When to use it
- Seed database rows
- Generate as many UUIDs as rows in your seed file and paste the list into a column.
- Build JSON fixtures
- Grab a batch for the id fields of mock API responses or test data.
- Add idempotency keys
- Copy a fresh UUID to use as a request key when testing payment or webhook APIs by hand.
Tips
- The third group of every v4 UUID starts with 4, and the fourth group starts with 8, 9, a or b. You can use that to spot whether an ID came from a v4 generator.
- Numbers above 50 are capped at 50 and anything below 1 becomes 1.
- Random v4 UUIDs do not sort by creation time, which can slow inserts on some database indexes. If ordering matters, consider a time-ordered ID format in your application code.
- To paste the list into a SQL IN clause or JSON array, run it through Find and Replace to wrap each line in quotes and add commas.
Questions
Can two generated UUID v4 values ever be the same?
In theory yes, but with 122 random bits the chance is so small that it is ignored in practice, even across billions of IDs. Most databases still add a unique constraint as a safety net.
Why can I only choose UUID version 4?
Version 4 is the random variant that suits nearly every ID need and needs no input. Name-based versions (v3, v5) and time-based ones (v1, v7) are not offered here.
Are these UUIDs uppercase or lowercase?
Lowercase, as returned by crypto.randomUUID. UUIDs are case-insensitive by specification, so convert them with the Case Converter if a system expects uppercase.
Is a UUID safe to use as a secret token?
A v4 UUID is hard to guess, but it was designed as an identifier, not a credential. For API keys or reset tokens, use a purpose-built random secret, such as a long password from the Password Generator.