Overview
Software constantly needs names for things that will never meet each other: a row in a database, an uploaded file, a session, an order. A UUID is a standardised answer to that need — a 128-bit identifier, usually written as 32 hexadecimal digits in five groups, that can be generated independently on any machine with almost no risk of two systems choosing the same value. No central counter, no permission to ask, no sequence to leak.
This tool produces version-4 UUIDs, the random kind. Sixteen bytes are drawn from your browser's cryptographic random source, a handful of bits are set to mark the version and variant, and the rest is pure chance. You can take a single value or a batch of up to fifty, switch the letter case, keep or drop the hyphens, copy the lot in one click, or save the batch as a plain text file for scripts and seed data.
What is a UUID?
UUID stands for universally unique identifier, and the format is defined by an internet standard (RFC 4122, now updated by RFC 9562). Written out, it looks like five groups of hex digits separated by hyphens — 8, 4, 4, 4 and 12 characters. Buried in the third group is a version number: a 4 there means the identifier was generated randomly, which is the version this page makes. The fourth group begins with a digit that identifies the variant, which keeps this layout distinct from older identifier schemes.
The remaining 122 bits are random, and that number is the reason collisions are a theoretical curiosity rather than a practical worry. You would need to generate roughly a billion UUIDs per second for a century before the odds of a single repeat became worth discussing. In everyday terms: if your application ever produces a duplicate random UUID, buy a lottery ticket, because something far stranger than a software bug has happened — check your random source first, though, since most real-world duplicates trace back to broken generation, not bad luck.
Features
- Genuine version-4 generation, with the version nibble set to 4 and the variant bits set to 10, exactly as the standard requires.
- Cryptographic randomness from crypto.getRandomValues — never Math.random, whose output can be predicted from a few samples.
- Batches of 1 to 50 in a single click, each value drawn independently.
- Uppercase toggle for systems and style guides that store identifiers in capitals.
- Optional hyphens — keep the familiar grouped layout, or strip the separators for compact 32-character strings.
- Copy All and text-file download, so a batch can go straight into a seed script, a fixture or a spreadsheet column.
- Instant, local and unlimited — no rate limits, no sign-up, and nothing about your values is transmitted or remembered.
Benefits
- No coordination needed. Two laptops on different continents can generate IDs all day without a shared counter or a check-in with a server.
- Nothing sensitive revealed. Unlike sequential IDs, a random UUID does not disclose how many records you created before it, or in what order.
- Database friendly. UUIDs work as primary keys that can be assigned before a row is inserted, which simplifies imports, merges and offline-first apps.
- Consistent format. Every mainstream language and database recognises the layout, so values move between systems without translation.
- Testing made easy. Fixtures and sample data get realistic, disposable identifiers in seconds.
Who can use it
Developers seeding a database, testers who need unique values in every run of a test suite, and data workers preparing import files where each row must arrive with its own key. It is also useful outside code: naming asset files so uploads never overwrite each other, tagging support exports, or generating a one-off reference for a form. Anyone who has ever typed "test123" as an ID and watched it collide will appreciate the upgrade.
How to use
- Enter how many identifiers you need, anywhere from a single UUID to a batch of fifty.
- Choose the format: lowercase is the most common convention, uppercase suits some legacy systems, and hyphens can be removed when a field accepts only 32 characters.
- Press Generate. Each press produces a completely fresh set — previous values are replaced, so copy anything you want to keep first.
- Use Copy All to place the whole set on your clipboard, one identifier per line.
- Or press Download .txt to save the batch as a plain text file named uuids.txt, ready for scripts and imports.
Frequently asked questions
Can two generated UUIDs ever be identical?
In principle, yes; in practice, the odds are so small that the format's designers treated it as a non-event. A version-4 UUID carries 122 random bits, giving about 5.3 × 10³⁶ possibilities. Duplicates that do occur in real systems almost always come from faulty generators — reused seeds, copied virtual machines, Math.random — rather than from chance.
What does "version 4" mean, and are there other versions?
The version digit records how the identifier was made. Version 1 combines a timestamp with a hardware address, versions 3 and 5 hash a name, and version 4 is the purely random one this page generates. Newer additions include version 7, which sorts by time. For general-purpose unique IDs with no ordering requirement, version 4 remains the common default.
Should UUIDs be uppercase or lowercase?
The standard writes them in lowercase, and that is the safest default for interoperability. Some systems display or store them in uppercase without harm, as long as comparisons are case-insensitive. Pick one convention per project and stay with it; this tool simply matches whatever your project already chose.
Are the hyphens required?
They are part of the canonical text layout, and most parsers expect them. A few fields — certain token formats and compact database columns — prefer the bare 32 hex characters. The value is the same identifier either way; the hyphens are punctuation, not data.
Is a UUID the same as a GUID?
Effectively, yes. GUID is Microsoft's name for its implementation of the same format, and the terms are used interchangeably in most documentation. A version-4 UUID from this page can be used anywhere a random GUID is requested.
Can I use these UUIDs in production?
Yes. They are standards-compliant and drawn from a cryptographic random source, which is exactly what production libraries do. Generate as many as your system needs, here or in your own code — the format guarantees they will coexist without a central registry.
Conclusion
When many systems need to name things without asking each other's permission, random UUIDs are the settled answer. Set the quantity, pick the case, and take a batch — each one fresh, standard and yours alone.