How to Generate UUIDs
A UUID is a 128-bit identifier that any system can generate independently with a vanishing chance of collision — no central registry, no coordination. This generator gives you the two versions that matter today. Version 4 is fully random and reveals nothing about its origin, making it the safe default for public identifiers. Version 7 embeds a millisecond timestamp at the front so identifiers sort chronologically, which keeps database indexes compact and inserts sequential — increasingly the preferred choice for primary keys. The NIL option produces the all-zero UUID when you need an explicit empty value. Choose how many you want, up to a hundred at a time, and adjust the formatting to match your system: uppercase hex, wrapped in braces, or with the hyphens stripped. All randomness comes from your browser's cryptographically secure generator rather than a predictable pseudo-random source, and nothing is transmitted anywhere. Copy one, copy them all, or download the batch as a text file.
Pick a version
Choose v4 for randomness, v7 for time-sortable, or NIL for a placeholder.
Set count & format
Generate up to 100 and toggle uppercase, braces or no hyphens.
Copy or download
Take one UUID, copy the whole list, or save it as a .txt file.
UUID Structure
The canonical format
Thirty-two hexadecimal digits in five hyphen-separated groups of 8-4-4-4-12, for example 3f2b1c4d-5e6f-4a7b-8c9d-0e1f2a3b4c5d. That's 36 characters including the hyphens.
Version & variant bits
The first character of the third group is the version — 4 or 7 here — and the first character of the fourth group encodes the variant. Those fixed bits are why a v4 UUID has 122 random bits rather than 128.
Common Use Cases
Database primary keys
Use v7 so new rows insert sequentially and indexes stay compact.
API resource IDs
Give each record a globally unique, non-guessable identifier.
Distributed systems
Let multiple services create IDs independently without collisions.
Test fixtures
Generate a batch of realistic identifiers for seed data.
File & object names
Name uploads uniquely without coordination.
Correlation IDs
Trace a request across services with a single unique token.
Idempotency keys
Give each operation a unique key so retries stay safe.
Session identifiers
Create unpredictable tokens for sessions and jobs.
Tips & Best Practices
Use v7 for primary keys
Time-ordered UUIDs keep index inserts sequential, avoiding the fragmentation random v4 causes.
Use v4 when time must stay private
v7 embeds a creation timestamp, so prefer v4 if that would leak useful information.
Store as binary if you can
A UUID is 16 bytes; storing it as a 36-character string wastes space in large tables.
Keep the format consistent
Pick one convention — lowercase with hyphens is standard — and use it everywhere.
Don't use UUIDs as secrets
They're unique, not secret. v4 is unpredictable, but treat real secrets as secrets.
NIL means empty, not missing
The all-zero UUID is an explicit placeholder; use null if a value is genuinely absent.
Troubleshooting
My v7 UUIDs look similar
That's expected — they share a timestamp prefix, which is exactly what makes them sortable. The tail is still random.
My system rejects the format
Some systems want uppercase, braces or no hyphens. Toggle the formatting options to match.
Are duplicates possible?
Practically no. With 122 random bits, you would need to generate billions per second for many years before a collision became likely.
The list didn't change
Press Generate for a fresh batch — changing formatting options only re-renders the existing UUIDs.
Frequently Asked Questions
How do I generate a UUID for free?
Pick a version and how many you need, and the UUIDs appear instantly. Copy or download them — free, no signup.
What is a UUID?
A 128-bit universally unique identifier, written as 32 hex digits in five hyphen-separated groups, that any system can generate independently.
What's the difference between v4 and v7?
v4 is fully random and reveals nothing; v7 starts with a timestamp so identifiers sort chronologically.
Which version should I use?
v7 for database primary keys where sort order helps; v4 when you don't want creation time embedded.
Are these UUIDs secure?
They use your browser's cryptographically secure random generator, so v4 values are unpredictable.
Can UUIDs collide?
In practice, no. With 122 bits of randomness the odds are negligible even at enormous scale.
How many can I generate at once?
Up to 100 in a single batch, which you can copy together or download as a text file.
What is the NIL UUID?
The all-zero UUID, used as an explicit placeholder when you need a valid but empty identifier.
Can I get uppercase UUIDs?
Yes. Toggle uppercase; you can also add braces or strip the hyphens to match your system.
Why do my v7 UUIDs share a prefix?
They encode the same millisecond timestamp. That shared prefix is what makes them sortable.
Are UUIDs sent to a server?
No. Everything is generated in your browser, so no identifier ever leaves your device.
Can I download the list?
Yes. Save the batch as a .txt file with one UUID per line, or copy them all at once.
Should I store UUIDs as text?
If your database supports a native UUID or binary type, use it — 16 bytes beats a 36-character string.
Are UUIDs suitable as secrets?
They're unique rather than secret. v4 is unpredictable, but use purpose-built tokens for real secrets.
What about UUID v1?
v1 embeds a MAC address and can leak hardware information. v7 gives you time ordering without that drawback.
Does it work offline?
Once the page has loaded it runs entirely in your browser, so it keeps working without a connection.
Does it work on phones?
Yes, in any modern browser on Windows, Mac, Android or iPhone with nothing to install.
Is this tool really free?
Completely free, forever — no account, no ads and no premium wall.
100% free · No signup · Generated in your browser · Never sent
Last updated: August 2026 · FlipMyFormat UUID Generator
Written and maintained by the FlipMyFormat team · Runs entirely in your browser