Free UUID Generator
Generate random v4 or time-ordered v7 UUIDs, up to 100 at a time. They are created in your browser and never touch our server.
What is a UUID Generator?
A UUID (universally unique identifier, also called a GUID) is a 128-bit value that systems can create independently with no realistic chance of a collision. A UUID generator produces them on demand.
This tool makes version 4 (random) and version 7 (time-ordered) UUIDs using your browser's cryptographic random source, so each value exists only on your device until you copy it.
- Choose v4 for a fully random value, or v7 for one that sorts by creation time.
- Set how many you need, up to 100, and any format options.
- Press Generate, then copy one value or the whole list.
Why Use This Generator?
- Secure randomness: values come from the Web Crypto API, not a predictable pseudo-random function.
- Current standard: v7 follows RFC 9562, the 2024 update to the UUID specification.
- Nothing transmitted: generation happens on your device, and we never see the values.
UUID Versions Compared
Versions differ in what fills the 128 bits. This tool generates v4 and v7.
| Version | Built from | When to use it |
|---|---|---|
| Version 1 | Time and node | The original time-based form. It can reveal when and where it was made, so v7 is usually the better pick. |
| Version 3 | MD5 of a name | The same name and namespace always give the same value. Prefer v5 for new work. |
| Version 4 | 122 random bits | The general-purpose default. It reveals nothing, and has no ordering. |
| Version 5 | SHA-1 of a name | A repeatable ID derived from a name, for when the same input must always map to the same UUID. |
| Version 7 | Timestamp and random bits | Sorts by creation time to the millisecond, which suits database primary keys. It does reveal when it was created. |
| Nil UUID | All zeros | A reserved placeholder that means no value. It is never a real identifier. |
How to Read a UUID
A UUID looks random, but a few positions carry meaning.
The version digit
Position 13The first digit of the third group gives the version, so a 4 or a 7 there tells you which kind you have.
The variant digit
Position 17The first digit of the fourth group is 8, 9, a or b for standard UUIDs.
36 characters
FormatThirty-two hex digits in groups of 8, 4, 4, 4 and 12. Without hyphens it is 32 characters, and case does not change the value.
Ordering inside a batch
Batchesv7 values sort by millisecond. Values made in the same millisecond share a timestamp, so their order within it is random.
Why UUIDs Exist
An auto-incrementing number needs one central counter. A UUID needs no coordination, so any server, phone or browser can create an ID that will not clash with another, even offline.
With 122 random bits, v4 collisions are so unlikely that systems treat them as impossible, provided the random source is sound.
v4 or v7?
Use v4 when an ID should reveal nothing. Use v7 for database keys: because new values sort after old ones, inserts land at the end of an index rather than scattering across it.
A quick rule:
- Public tokens: v4, since v7 exposes the creation time.
- Primary keys: v7, for better index locality.
Where UUIDs Trip People Up
UUIDs are simple to create and easy to misuse. Watch for these:
- A UUID is not a secret. It is hard to guess, but it is not an access control. For tokens and API keys, use a random string with enough entropy and treat it as a credential.
- Math.random is not enough. Generators built on it can repeat or be predicted. Use a cryptographic source, as this tool does.
- Store them as binary where you can. As text a UUID takes 36 bytes; as a native or binary column it takes 16.
- Compare them case-insensitively. Some systems emit uppercase and others lowercase, and the value is the same.
Why Teams Choose UUIDs
No central counter
Services create IDs independently, with no round trip to a database.
Safe merges
Records from two systems can be combined without renumbering anything.
No enumeration
Sequential IDs show how many records you have and invite scraping. Random ones do neither.
Friendly indexes
v7 keeps the benefits of a UUID while inserting in order, which random v4 keys cannot do.
Who Generates UUIDs
Most people need one quickly, for a very specific job.
Site Operators
Tag records and jobs while running the domains behind a product.
See domain monitoringRelated Tools
More utilities, and the monitoring behind them.
Generate random strings
Create tokens and passwords with the length and characters you choose.
Random string generatorMonitor your domains
Get an alert when a domain's expiry, DNS or certificate changes.
See domain monitoringFrequently Asked Questions
Common questions about UUIDs.
What is the difference between a UUID and a GUID?
Nothing practical. GUID is Microsoft's name for the same 128-bit identifier.
Are these UUIDs safe to use in production?
Yes. They come from the Web Crypto API, the same kind of source a server-side library relies on, and follow the RFC 9562 layout.
Can two UUIDs ever be the same?
In theory, yes. In practice, a v4 UUID has 122 random bits, so you can treat a collision as something that will not happen.
Does Domainyze store the UUIDs I generate?
No. They are created in your browser and are never sent to us.
Which version should I use for a database primary key?
Version 7. It sorts by time, so inserts stay close together in the index.
Does a UUID v7 reveal anything?
Yes, its creation time to the millisecond. Use v4 if that matters.
Why is there no v1 option?
RFC 9562 recommends v7 over v1 for new systems, so this tool offers the two versions most people should choose from.
Should I use uppercase or lowercase?
Lowercase is the standard output, and uppercase is accepted on input. Pick one and stay with it.
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