UUID Generator: Create v4 & v7 UUIDs in Bulk

How to use the UUID Generator

1Choose Version 4 for random IDs or Version 7 for IDs that sort by creation time.

2Enter how many you need, from 1 to 1,000.

3Pick a format: uppercase, without hyphens, in braces, or as a quoted list for code and SQL.

4Copy the UUIDs or download them as a .txt file.

5To check an existing UUID, paste it under Check a UUID to see its version, variant and creation time.

What a UUID is

A UUID (universally unique identifier) is a 128-bit number, written as 32 hexadecimal digits in five groups: 919108f7-52d1-4320-9bac-f847db4148a8. Anyone can create one on any device, with no central counter, and still be confident nobody else will ever create the same value. That is why UUIDs label database rows, files, orders, devices and API requests.

The current standard is RFC 9562 (published in 2024), which replaced the older RFC 4122. Two small parts of every standard UUID are fixed:

The version digit is the first digit of the third group. In 4320 it is 4.
The variant digit is the first digit of the fourth group. For standard UUIDs it is 8, 9, a or b, as in 9bac.

Everything else is either random or, for time-based versions, a timestamp.

Version 4 or version 7?

This generator makes the two versions most people need:

	Version 4	Version 7
First 48 bits	Random	Unix time in milliseconds
Random bits	122	74 (random, or a counter within the same millisecond)
Sorts by creation time	No	Yes
Reveals when it was made	No	Yes, to the millisecond
Best for	General IDs, test data, file names	Database keys, logs, events

Version 4 is the safe default. It is almost entirely random, so it reveals nothing about when or where it was made.

Version 7 puts the time first. New IDs sort after older ones, so a database index grows at one end instead of being scattered at random. That keeps inserts fast on large tables, which is why v7 is now the usual choice for primary keys. The generator follows the standard’s advice to keep v7 IDs in order even when many are made in the same millisecond, so a bulk batch is already sorted.

Worked example: the time inside a v7 UUID

Take the example from RFC 9562: 017f22e2-79b0-7cc3-98c4-dc0c0c07398f.

The first 12 hex digits, 017f22e279b0, are the timestamp. In decimal that is 1,645,557,742,000 milliseconds after 1 January 1970.
That moment is 22 February 2022, 19:22:22 UTC.
The 7 that starts the third group is the version, and the 9 that starts the fourth group marks a standard UUID.

Paste it into Check a UUID above and the tool shows the same date. It also reads the time inside version 1 and version 6 UUIDs, which count in 100-nanosecond steps from 15 October 1582, the start of the Gregorian calendar.

How unlikely is a duplicate?

For version 4, duplicates follow the “birthday problem”. With n random UUIDs, the chance that any two match is roughly:

p ≈ n² ÷ 2¹²³

Generate one billion v4 UUIDs and p is about 0.00000000000000000009. You would need around 2.7 quintillion (2.7 × 10¹⁸) before a single duplicate became a coin flip. In practice the real risk is not the maths but a weak random number generator. This tool uses your browser’s cryptographic generator, the same one used for encryption keys.

Formats you will meet

All of these are the same 128-bit value, just written differently:

Format	Example	Where you see it
Standard	`919108f7-52d1-4320-9bac-f847db4148a8`	Most APIs and databases
Uppercase in braces	`{919108F7-52D1-4320-9BAC-F847DB4148A8}`	Windows, .NET and the registry, where it is called a GUID
No hyphens	`919108f752d143209bacf847db4148a8`	Compact storage and file names
URN	`urn:uuid:919108f7-52d1-4320-9bac-f847db4148a8`	XML and some standards

The standard says to write UUIDs in lowercase but to accept uppercase, so comparisons should ignore case. The checker accepts every form above, plus quotes and trailing commas copied from code.

Two special values exist. The Nil UUID is all zeros and usually means “no value”. The Max UUID is all f digits and was added in RFC 9562 as a sentinel.

Tips

Store UUIDs as UUIDs. Databases such as PostgreSQL have a native uuid type that uses 16 bytes. Storing the 36-character text form takes more than twice the space and makes indexes slower.
Use the list formats for code. Quoted, comma-separated output drops straight into a JSON array, a JavaScript array or an SQL IN (…) list. Tidy the result with the JSON formatter.
Don’t treat a UUID as a secret. IDs tend to appear in URLs and logs, and a v7 UUID reveals its creation time. For passwords and API keys use the password generator.
Need a fingerprint, not an ID? A UUID is random; a hash is calculated from data. To check that a file hasn’t changed, use the hash generator.

Every UUID here is generated in your browser. Nothing is sent to a server or stored, so you can use them freely in private projects.

Frequently asked questions

What is the difference between UUID v4 and v7?

Version 4 is almost entirely random. Version 7 starts with a timestamp in milliseconds followed by random bits, so v7 UUIDs sort in the order they were created, which keeps database indexes compact.

Can two UUIDs ever be the same?

In theory yes, in practice no. A v4 UUID has 122 random bits, so you would need to generate about 2.7 quintillion of them before the chance of a single duplicate reached 50%.

Is a GUID the same as a UUID?

Yes. GUID is Microsoft’s name for the same 128-bit identifier. GUIDs are often written in uppercase inside braces, which you can switch on here.

Should I use UUIDs as database primary keys?

They work well when IDs are created in many places at once. Prefer v7: because new values sort after old ones, inserts stay fast, while random v4 keys scatter writes across the index.

Can I use a UUID as a password or secret token?

Treat UUIDs as identifiers, not secrets. The v4 UUIDs made here come from your browser’s cryptographic random generator, but v7 reveals when it was created, and many systems log IDs openly. Use a long random password for secrets.

Are the UUIDs generated on a server?

No. They are created in your browser with its built-in secure random number generator, and nothing is sent or stored anywhere.