UUID Generator
Generate version 4, version 7, version 1 and version 5 UUIDs in bulk, in the format you need. Copy them or download a file, and check any UUID to see its version and timestamp.
Generate UUIDs
Check a UUID
Paste any UUID to see whether it is valid, which version and variant it uses, and the timestamp inside version 1 and version 7 UUIDs.
Free Online UUID Generator
A UUID (universally unique identifier) is a 128-bit value used to identify things without a central authority handing out numbers. It is written as 32 hexadecimal digits in five groups, such as 550e8400-e29b-41d4-a716-446655440000. Databases, APIs, message queues and file systems use UUIDs because two systems can create IDs independently and still be almost certain they will never clash. This tool generates UUIDs in bulk in your browser, using your device’s secure random number generator. Nothing is sent to a server.
How to Use the UUID Generator
- Pick a Version. Version 4 is the usual choice for random IDs.
- Enter how many UUIDs you want, from 1 to 10,000.
- Choose the Format (lowercase, uppercase, no hyphens, braces or URN) and how the list should be written.
- Press Generate, then Copy or Download File.
- Use Check a UUID to inspect any UUID you already have.
UUID Versions Explained
| Version | How it is made | Best for |
|---|---|---|
| Version 4 | 122 random bits. The rest of the bits mark the version and variant. | General purpose IDs, session identifiers, test data. |
| Version 7 | A 48-bit Unix timestamp in milliseconds followed by random bits, so newer IDs sort after older ones. | Database primary keys and any place where sorted IDs improve performance. |
| Version 1 | A 60-bit timestamp, a clock sequence and a node ID. This tool uses a random node ID, not your network card. | Compatibility with older systems that expect time-based IDs. |
| Version 5 | A SHA-1 hash of a namespace and a name. The same input always gives the same UUID. | Stable IDs derived from names, such as a URL or a domain. |
| Nil and Max | All zeros (nil) or all ones (max). | Placeholder and sentinel values. |
Version 4 or Version 7?
Random version 4 UUIDs are scattered across the whole range, so inserting them into a database index touches many different pages. Version 7 UUIDs start with the time, so new rows land at the end of the index, which is usually faster and keeps the index compact. Version 7 also lets you sort IDs by creation time. The cost is that a version 7 UUID reveals when it was created. Choose version 4 when the ID should reveal nothing, and version 7 when ordering and database speed matter.
Formats
| Format | Example |
|---|---|
| Standard | 550e8400-e29b-41d4-a716-446655440000 |
| Uppercase | 550E8400-E29B-41D4-A716-446655440000 |
| No hyphens | 550e8400e29b41d4a716446655440000 |
| Braces | {550e8400-e29b-41d4-a716-446655440000} |
| URN | urn:uuid:550e8400-e29b-41d4-a716-446655440000 |
Uppercase and lowercase UUIDs are the same value. The standard recommends writing them in lowercase.
Can Two UUIDs Be the Same?
In theory yes, but in practice no. A random version 4 UUID has 122 random bits, which gives about 5.3 × 1036 possible values. You would need to generate roughly 2.7 billion billion UUIDs before there is even a 50% chance of one repeat. A bug in how random numbers are produced is far more likely to cause a clash than chance, which is why this tool uses the browser’s cryptographic generator.
Good Practices
- Store UUIDs in a native UUID or 16-byte binary column if your database has one. It is smaller and faster than a 36-character string.
- Do not treat a UUID as a password. It is an identifier. Use proper tokens for authentication.
- Remember that version 1 and 7 contain a timestamp, which may be information you do not want to share.
Privacy
UUIDs are generated in your browser with the Web Crypto API. The page does not send, store or log what you generate.
Frequently Asked Questions (FAQ)
Is the UUID generator free?
Yes. It is free, needs no sign-up and can create up to 10,000 UUIDs at a time.
What is the difference between a UUID and a GUID?
They are the same 128-bit format. GUID is the name Microsoft uses, and some Microsoft tools show it in uppercase with braces.
Which UUID version should I use?
Use version 4 for random IDs, and version 7 when you want IDs that sort by creation time, such as database keys.
Are the UUIDs generated here truly random?
Version 4 and the random parts of versions 7 and 1 come from the browser’s cryptographic random generator, the same source used for secure connections.
Why do version 5 UUIDs repeat?
Version 5 is deterministic. The same namespace and name always give the same UUID, so the quantity is fixed at one.
Does version 1 expose my computer’s MAC address?
No. This tool uses a random node ID instead of a hardware address, as the standard allows.
What is a nil UUID?
It is the special value with all 128 bits set to zero. It is used as an empty or unknown value.