How to generate UUIDs
- 1Choose a Format: Standard, No hyphens, Uppercase, or Braced (the {...} style used for Windows and .NET GUIDs).
- 2Set Count to how many you need, anywhere from 1 to 1,000.
- 3Click Generate. The list appears in the Generated UUIDs panel, one per line.
- 4Click Copy all to put them on your clipboard, or Save to download them as uuids.txt.
What is a UUID v4, and can two ever collide?
A UUID (universally unique identifier) is a 128-bit value written as 32 hex digits in five groups, like 3f2a8c1e-7b4d-4e9a-b1c6-0d5e8f7a2b3c. The format is defined in RFC 4122, now updated by RFC 9562. Microsoft calls the same thing a GUID. Several versions exist. This tool is a UUID v4 generator, and version 4 is almost entirely random: 122 bits come from a random number generator, and the remaining 6 bits mark the version (the 4 at the start of the third group) and the variant.
Those 122 random bits are why you can generate IDs on any machine, with no coordination, and still trust them to be unique. There are about 5.3 x 10^36 possible v4 UUIDs. By the birthday bound, you would need to generate roughly 2.7 quintillion (2.7 x 10^18) of them before the chance of a single duplicate reached 50%. That is a billion UUIDs a second for about 86 years. In practice a collision is far less likely than a hardware fault corrupting your data.
That guarantee depends on good randomness. This tool uses crypto.randomUUID, which draws from the browser's cryptographically secure random number generator. Hand-rolled UUID code built on Math.random has caused real duplicate-ID bugs, because its output can be predictable and its internal state is small.
Random UUIDs have one trade-off: they don't sort by creation time, so as primary keys they scatter inserts across a B-tree index. If insert order matters, look at time-ordered formats such as UUID v7. For tokens, correlation IDs, file names and most primary keys, v4 is the simple, safe default.
When developers reach for it
Database primary keys and fixtures
Generate UUIDs in a batch for seed data, migrations or test fixtures without waiting on a database sequence.
Request and correlation IDs
Grab a UUID to tag a request, job or log trace while debugging distributed services.
.NET and Windows GUIDs
Use the Braced or Uppercase format for registry keys, COM class IDs, Visual Studio project files and WiX installers.
Compact identifiers
Switch to No hyphens for a UUID without hyphens, a 32-character hex string that fits in URLs, filenames or systems that reject dashes.
Frequently asked questions
What's the difference between a GUID and a UUID?
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Nothing technical. GUID is Microsoft's name for the same 128-bit identifier defined by RFC 4122 (now RFC 9562), so a v4 UUID from this page works anywhere a GUID is expected. The Braced format adds the curly braces that some Windows and .NET tools show around GUIDs.
Are these UUIDs truly random?
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Yes. They're version 4 UUIDs created with crypto.randomUUID, which uses the browser's cryptographically secure random number generator. Each one has 122 random bits.
What's the difference between a UUID and a GUID?
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Nothing technical. GUID is Microsoft's name for the same 128-bit identifier. GUIDs are often written in uppercase and wrapped in braces, which is what the Uppercase and Braced formats produce.
Can two v4 UUIDs ever be the same?
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In theory yes, in practice no. You'd need to generate around 2.7 x 10^18 UUIDs before the chance of even one duplicate reached 50%.
Can I use a UUID as a secret token?
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A v4 UUID from a secure generator has 122 bits of randomness, which is hard to guess, but the UUID spec doesn't promise unguessability. For API keys or session secrets, use a purpose-built random key generator instead.
Is a GUID generator online safe to use for production IDs?
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This one is, because nothing is generated on a server: the IDs come from crypto.randomUUID in your browser, so no one else has seen them. Uniqueness depends on the quality of the random source, not on where you run it.
How many UUIDs can I generate at once?
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Up to 1,000 per click, so it works as a bulk UUID generator for seed files and load tests. Copy them all to your clipboard or save them as a plain text file with one UUID per line.
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