UUID Generator: Generate Random UUID v4, v7 and GUIDs Online
Generate one UUID or thousands in a click. This free UUID generator creates random version 4 UUIDs and time-ordered version 7 UUIDs, and it works as a GUID generator too. Pick the quantity, switch between lowercase and uppercase, add or remove hyphens, wrap values in braces or quotes, and copy or download the list. Everything is made in your browser using a secure random source, so nothing is sent to a server and nothing is stored.
Use it to create database keys, test data, request IDs, file names, session tokens for demos, or placeholder IDs for an API. Below the tool you will find what each UUID version means, how unique a UUID really is, and code to generate them yourself.
Use the toolYour UUIDs
Details
v4 and v7
Random or time-ordered UUIDs and GUIDs.
Up to 1,000 at once
Bulk lists for test data and fixtures.
Format options
Uppercase, no hyphens, braces, quotes, JSON array.
Made in your browser
Web Crypto random numbers. Nothing is uploaded.
Choose v4 or v7, set the quantity and press Generate. Change the format with the options, then copy one UUID, copy the whole list or download it as a text file. The Check a UUID tab tells you what a UUID is.
Key Takeaways
- A UUID is a 128-bit identifier. A GUID is the same thing under Microsoft's name.
- v4 is almost entirely random, with 122 random bits. v7 starts with a timestamp, so it sorts by creation time.
- Collisions are extremely unlikely with a good random source, which this tool uses.
- Unique does not mean secret. Do not use a UUID as a password or an API key.
- UUIDs are made in your browser and never uploaded or stored.
How to Generate a UUID Online
-
1STEP 1 Choose the version: v4 for fully random IDs, or v7 if you want IDs that sort by creation time.
-
2STEP 2 Set how many UUIDs you need, from 1 up to 1,000.
-
3STEP 3 Choose the format: lowercase with hyphens is standard, or turn on uppercase, braces, quotes or no hyphens.
-
4STEP 4 Click Generate. The list appears at once, and you can generate again for a fresh set.
-
5STEP 5 Copy one UUID, copy the whole list or download it as a text file.
What Is a UUID?
A UUID (universally unique identifier) is a 128-bit label used to identify things without a central authority handing out numbers. It is written as 32 hexadecimal characters in five groups separated by hyphens, in the pattern 8-4-4-4-12. For example:
43aa8d6a-306e-405e-a931-eda2d103e7ce
Because any computer can create a UUID on its own, with an extremely low chance of repeating one made anywhere else, UUIDs are widely used as keys in databases and distributed systems. The format is defined by the RFC 4122 standard, and the newer RFC 9562 adds versions such as v7.
UUID vs GUID: What Is the Difference?
A GUID (globally unique identifier) is the name Microsoft uses for the same thing. In practice a GUID and a UUID have the same 128-bit structure and the same text format, so values from this tool work as a GUID generator output. The main visible difference is style: .NET and SQL Server often show GUIDs in uppercase or inside curly braces, while many other systems use lowercase with no braces. The format toggles above cover both.
UUID Versions Explained
| Version | How it is made | Best used for |
|---|---|---|
| v1 | Timestamp plus the machine node identifier (often a MAC address) | Older systems. It can reveal when and where it was made, so avoid it for public IDs |
| v3 and v5 | A hash of a name and a namespace (MD5 for v3, SHA-1 for v5) | Stable IDs: the same name always gives the same UUID |
| v4 | Random numbers (122 random bits) | The default choice for most apps, tests and tokens |
| v7 | A Unix timestamp in milliseconds followed by random bits | Database primary keys, because new IDs sort in creation order |
| Nil | All zeros: 00000000-0000-0000-0000-000000000000 | A placeholder meaning no value |
UUID v4: random UUIDs
A version 4 UUID is made almost entirely from random bits. Six bits are fixed to mark the version and variant, leaving 122 random bits. You can spot a v4 UUID because the first character of the third group is always 4, and the first character of the fourth group is 8, 9, a or b. In the example above, the third group starts with a 4.
UUID v7: time-ordered UUIDs
A version 7 UUID starts with a 48-bit timestamp in milliseconds and fills the rest with random bits. Because the timestamp comes first, UUIDs made later sort after earlier ones. That keeps database indexes tidy and makes inserts faster than with fully random keys, while still hiding any machine details. The trade-off is that a v7 UUID reveals roughly when it was created, which matters if creation time should stay private.
UUID v4 vs v7: which should I use?
- Choose v4 when you want pure randomness and the ID should reveal nothing, such as public links or tokens for sharing.
- Choose v7 for database primary keys and event logs, where sorted order and index performance help.
- Choose v5 when you need the same input to always produce the same ID.
How Unique Is a UUID? Can Two UUIDs Collide?
A v4 UUID has 122 random bits, which gives about 5.3 undecillion (5.3 followed by 36 zeros) possible values. The chance of making the same one twice is very small. By the usual birthday-problem estimate, you would need to generate around 2.7 quintillion v4 UUIDs before the odds of any duplicate reach 50 percent. For normal applications, treat collisions as practically impossible, as long as the random numbers come from a good source.
That last point matters. This tool uses the browser secure random generator, not a simple pseudo random function. Weak random sources, such as Math.random in older code, are the real cause of most collisions seen in practice.
UUID Format Options
| Format | Example | Where it is common |
|---|---|---|
| Standard lowercase | 5f7e11c6-723f-4cd6-9563-74d9082485f6 | Most languages, APIs and PostgreSQL |
| Uppercase | 5F7E11C6-723F-4CD6-9563-74D9082485F6 | .NET and SQL Server output |
| No hyphens | 5f7e11c6723f4cd6956374d9082485f6 | Compact IDs, file names, some databases |
| Braces | {5F7E11C6-723F-4CD6-9563-74D9082485F6} | Windows registry and COM style |
How to Generate a UUID in Code
If you need UUIDs inside your own program, most languages can make them without a library. These are common one-liners:
| Language | Code |
|---|---|
| JavaScript (browser and Node) | crypto.randomUUID() |
| Python | import uuid; str(uuid.uuid4()) |
| PostgreSQL | SELECT gen_random_uuid(); |
| C# (.NET) | Guid.NewGuid().ToString() |
| Java | java.util.UUID.randomUUID().toString() |
| SQL Server | SELECT NEWID(); |
Support for v7 depends on your language version and libraries, so check your documentation. This online UUID generator is useful when you just need a batch for a test or a spreadsheet.
UUIDs as Database Primary Keys
UUIDs make good primary keys when many systems create records on their own or when you do not want IDs that can be guessed in order. The cost is size: a UUID takes 16 bytes in binary form, against 4 or 8 for an integer, and fully random v4 keys can scatter inserts across an index. Storing UUIDs in a native UUID column type, not as text, and using time-ordered v7 keys, can reduce both problems.
Common Uses of UUIDs
- Primary keys and foreign keys in databases.
- Unique file and upload names, so two users never overwrite each other.
- Request and correlation IDs for tracing a call across services.
- Order, invoice or booking references where sequential numbers would be guessable.
- Test data, fixtures and mock API responses.
- Device, session and event IDs in apps and analytics.
Is a UUID Secure? Should I Use It as a Password or Token?
A UUID is unique, but unique does not mean secret. A v4 UUID has plenty of randomness for hard-to-guess links, yet it should not replace passwords, and a UUID that was ever shown or logged should not be treated as a secure key. For access tokens and API keys, use a dedicated secure token generator and follow the guidance of your framework.
Is This UUID Generator Private?
Yes. UUIDs are made in your browser using the Web Crypto API. They are not generated on a server, uploaded or stored, so nobody else sees the IDs you create.
More Free Developer and Text Tools
Working with data? Tidy it up with the JSON Formatter or XML Formatter, format queries with the SQL Formatter, or turn text into binary with the Binary Translator converter. Need other random values? Try the Random Word Generator or the Random Name Picker.
FAQs
What is a UUID generator?
A UUID generator creates universally unique identifiers, which are 128-bit values written as 32 hexadecimal characters in five hyphen-separated groups. You choose a version, such as random v4 or time-ordered v7, set how many you need, and copy the results. They are used as database keys, file names and request IDs.
What is the difference between UUID and GUID?
They are the same kind of 128-bit identifier. GUID is the term used by Microsoft, and UUID is the term used in the wider standard. Both use the same structure and text format. GUIDs from .NET and SQL Server are often shown in uppercase or in curly braces, but the value itself is compatible.
What is the difference between UUID v4 and v7?
A v4 UUID is built from random bits, so it has no order. A v7 UUID begins with a millisecond timestamp, so newer IDs sort after older ones while the rest stays random. V7 works better as a database key, and v4 is better when the ID should reveal nothing about when it was made.
Can two UUIDs be the same?
In theory yes, in practice almost never. A v4 UUID has 122 random bits, and you would need to generate roughly 2.7 quintillion of them to reach even odds of one duplicate. Collisions seen in the real world usually come from poor random number sources or copied values, not from the format.
How do I generate a UUID in JavaScript, Python or SQL?
In JavaScript use crypto.randomUUID(). In Python use str(uuid.uuid4()). In PostgreSQL use gen_random_uuid(), and in SQL Server use NEWID(). C# uses Guid.NewGuid() and Java uses UUID.randomUUID(). For a quick batch without writing code, use this online generator and copy the list.
Is a UUID safe to use as a secret token?
Not on its own. A v4 UUID is hard to guess, but it is meant to be an identifier, not a secret, and it often ends up in logs and URLs. For passwords, session tokens and API keys, use a purpose-built secure token generator from your framework and store secrets with care.
Why does the third group of a UUID start with 4?
The first digit of the third group marks the version. A 4 means the UUID is version 4, made from random numbers, and a 7 means version 7. The first digit of the fourth group, which is 8, 9, a or b in these versions, marks the variant defined by the standard.
Are the UUIDs I generate stored anywhere?
No. They are created in your browser with the secure random generator and are not sent to a server or saved. When you close or refresh the page, the list is gone, so copy or download anything you need to keep. Nobody else can see the IDs you generate.
Related Free Tools
JSON Formatter
Beautify, validate and minify JSON in your browser.
Open the toolXML Formatter
Format, validate and minify XML in your browser.
Open the toolPassword Generator
Create strong random passwords and passphrases.
Open the toolRandom Word Generator
Random words by type, length and letter.
Open the toolReady to generate UUIDs?
Go back to the generator, set the quantity and press Generate.
Use the tool