A UUID is a 128 bit universally unique identifier, written as 32 hexadecimal digits in the pattern 8-4-4-4-12, that labels a thing with effectively no chance of clashing with any other identifier. The generator below produces version 4 UUIDs (also called GUIDs) entirely in your browser from a cryptographic random source, so each value is unique, standards correct, and never sent over the internet.
What a UUID Is
A UUID, or universally unique identifier, is a 128 bit number used to label something so it can be told apart from every other thing without asking a central server for an ID. It is written as 32 hexadecimal characters split by hyphens into five groups, for example 3f2504e0-4f89-41d3-9a0c-0305e82c3301. Microsoft calls the same value a GUID, a globally unique identifier, so the two terms mean the same format and are interchangeable.
How to Use This UUID Generator
- Choose how many UUIDs you need: 1, 5, or 10.
- Press Generate new UUID, or change the count, to produce a fresh set.
- Press Copy all to copy every UUID to your clipboard at once.
- Paste them into your code, database seed, config file, or test data.
How a Version 4 UUID Works
A version 4 UUID is almost entirely random. Of its 128 bits, 6 are fixed to record the version and the variant, and the remaining 122 are filled from a cryptographic random source. The version digit (the 4) sits at the start of the third group, and the variant marker sits at the start of the fourth. The 8-4-4-4-12 format is just those 16 bytes shown as hexadecimal with hyphens. With 122 random bits there are over five undecillion possible values, so the chance of two generated UUIDs colliding is so small it is treated as zero in practice.
Where UUIDs Are Used
UUIDs are most common as database primary keys, because a service can create a new record with its own ID and never clash with IDs created elsewhere. That makes them a natural fit for distributed systems, where many servers write data at once with no shared counter to coordinate. You also see UUIDs as request and trace identifiers in logs, as file and object names that must not collide, and as keys in API responses where exposing a sequential integer would leak how many records exist.
Is It Private? Yes, It Runs in Your Browser
Every UUID here is generated locally on your device using the Web Crypto random source, and nothing is uploaded, logged, or stored on any server. It is safe to generate identifiers for production code even on a shared or public network, because the values never leave your browser.
Related Tools
Paste a UUID to check its format, version, and variant.
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Format and validate JSON, where UUID keys often live.
Last Thoughts on UUIDs
The point of a UUID is independence: any service can mint an identifier that will not collide with one minted somewhere else, with no central authority and no coordination. A version 4 UUID delivers that with pure randomness, which is why it has become the default identifier for distributed systems, message queues, and modern database schemas.
Generate the IDs you need above and paste them straight into your project. For the wider picture of how these keys fit into a schema, see our guide on what a database is, and explore the rest of our free online tools.
Key Takeaways:
- A UUID is a 128 bit identifier written as 32 hexadecimal digits in the 8-4-4-4-12 pattern.
- UUID and GUID are two names for the same value; GUID is Microsoft naming.
- A version 4 UUID is 122 random bits plus fixed version and variant markers, set per RFC 4122.
- Collisions are so unlikely that systems mint UUIDs independently with no central registry.
- UUIDs suit database keys and distributed systems where many servers create records at once.
- This generator runs entirely in your browser using a cryptographic random source; nothing is sent anywhere.
Frequently Asked Questions (FAQs)
What is the difference between a UUID and a GUID?
There is no functional difference. UUID (universally unique identifier) is the name used in the RFC 4122 standard and across most platforms, while GUID (globally unique identifier) is the name Microsoft uses for the same 128 bit value. Both describe the same format, the same bit layout, and the same uniqueness guarantee, so a UUID and a GUID are interchangeable.
Are version 4 UUIDs really unique?
For all practical purposes, yes. A version 4 UUID has 122 random bits, which gives more than five undecillion possible values. You would need to generate billions of UUIDs every second for many years before the chance of a single collision became worth worrying about, which is why applications treat them as unique without a central authority checking.
Is this UUID generator safe to use for production code?
Yes. The values come from the browser cryptographic random source, the same source used for security tokens, and the version and variant bits are set exactly as RFC 4122 requires. You can copy the output straight into a database seed, a config file, or test data. For high volume generation inside an application, call your platform native UUID function instead of a web page.
Does this tool send my UUIDs to a server?
No. Every UUID is created entirely inside your browser and is never transmitted, logged, or stored on any server. You can confirm this by disconnecting from the internet and watching the generator still work.
Can a UUID be used as a database primary key?
Yes, and it is a common choice for distributed systems. A UUID lets two services create records independently without coordinating on an auto increment counter, so there is no central bottleneck and no clash when records are merged. The tradeoff is that a random UUID is larger and less index friendly than a sequential integer, which matters at very large scale.
What does the version 4 in a UUID mean?
The version number records how the UUID was produced. Version 4 means the value is almost entirely random, as opposed to version 1 which is based on time and a hardware address. You can read the version from the UUID itself: the digit at the start of the third group is the version, so a 4 there marks a version 4 UUID.
