Overview
Software constantly needs names for things that will never meet: a database row, an uploaded file, a session, an order number. Asking a central counter for each one creates a bottleneck and leaks information about how many things exist. A UUID solves it differently — it's a 128-bit identifier in a standard written format that any machine can generate on its own, with such a tiny chance of collision that, for practical purposes, every value is unique. No permission, no coordination, no sequence to guess.
This page produces version-4 UUIDs, the random kind. Sixteen bytes come from your browser's cryptographic random source; a few bits are then fixed to mark the version and variant exactly as the standard requires, and the rest is pure chance. Take one value or a batch of up to fifty, flip the letter case, keep or drop the hyphens, copy everything with one click, or download the batch as a plain text file for scripts and seed data.
What is a UUID?
UUID stands for universally unique identifier, and the layout is defined by an internet standard. Written out, it's 32 hexadecimal digits in five groups — 8, 4, 4, 4 and 12 characters — separated by hyphens. Hidden in the third group is a version digit; a 4 there means the value was generated randomly, which is what this tool makes. The fourth group starts with a digit marking the variant, keeping this scheme distinct from older identifier formats.
The remaining 122 bits are random, and that number is why collisions are a theoretical curiosity rather than a real worry. You'd need to generate absurd quantities — roughly a billion per second for a century — before a single repeat became statistically worth mentioning. In plain terms: if your app ever produces two identical random UUIDs, check your random number source first, because genuine collisions basically don't happen.
Features
- Batches of 1 to 50. One identifier for a quick test, or fifty for a data import — you choose the count.
- True version-4 format. The version nibble reads 4 and the variant bits are set exactly as the standard demands.
- Uppercase option. Flip the hex digits to capitals for systems that expect that style.
- Hyphens on or off. Keep the classic grouped format or get a compact 32-character string.
- Copy all in one click. The whole batch lands on your clipboard, one UUID per line.
- Download as .txt. Save the batch as a plain text file, ready for scripts and seed data.
- Cryptographic randomness. Values come from your browser's secure random source, not a weak shuffle.
Benefits
- Unique without coordination. Generate IDs on any machine with no central counter and no duplicates to fear.
- Standard-compliant. Any database, API or library that accepts UUIDs will accept these.
- Batch-friendly. Fifty values in one go beats clicking a single-value generator fifty times.
- Private by default. Everything is created locally; nothing is sent or stored anywhere.
Who can use it
Developers are the main audience: seeding test databases, generating primary keys, naming uploaded files, creating session tokens, or mocking API responses. QA engineers use batches to stress-test imports. Data folks minting identifiers for migrated rows get collision-free values without a round trip to the database. Even non-developers occasionally need a random unique string — for a raffle, a survey token, or anonymising a spreadsheet column. If you need 'a unique label for each thing, right now', this is the fastest honest way to get one.
How to use
- Set how many UUIDs you need — anywhere from 1 to 50.
- Choose uppercase if your system expects capital hex digits; leave it off otherwise.
- Keep hyphens for the standard readable format, or switch them off for a compact string.
- Press Generate and inspect the batch.
- Copy all to the clipboard, or download the batch as a .txt file for your scripts.
Frequently asked questions
What does 'version 4' mean?
It's the variant of UUID built from random numbers. The standard defines several versions: version 1 embeds a timestamp and machine address, version 4 is pure randomness. A single digit inside the identifier records which version it is, so any software reading it knows how it was made. Version 4 is the right choice whenever you just need a unique random value with no information baked in — which covers the vast majority of everyday uses.
Could two UUIDs ever be the same?
In theory, yes; in practice, no. With 122 random bits, the odds of a repeat are so small that you'd need to generate about a billion UUIDs every second for a hundred years before expecting a single collision. If you ever do see a duplicate, the cause is almost certainly a broken random number generator or the same value being copied twice — not bad luck. For any real application, treat version-4 UUIDs as unique.
Should I keep the hyphens or remove them?
Keep them unless you have a reason not to. The hyphenated form — eight, four, four, four, twelve characters — is the canonical layout that databases, APIs and humans all recognise at a glance. The compact 32-character form is useful when a system has strict length limits or forbids punctuation, such as some filenames or URL slugs. Both forms represent the identical 128-bit value; it's purely a formatting choice.
Uppercase or lowercase hex — does it matter?
The value is identical either way; hexadecimal digits don't change meaning with case. Lowercase is the common convention you'll see in documentation and most tools. Some systems — certain enterprise databases, Windows-style GUID displays — traditionally show uppercase. Match whatever your destination expects for consistency, but don't worry: any UUID-aware software accepts both.
Are these safe to use as database primary keys?
Yes, that's one of their most common jobs. Random UUIDs make excellent primary keys when rows are created across many machines or offline, because no coordination is needed to avoid clashes. Two honest caveats: they're larger than integer keys, so indexes grow, and their randomness can fragment certain index types. For most applications those costs are negligible compared to the simplicity. If your database has a native UUID type, use it.
Do I need an account or install anything?
No. The page draws random bytes from your browser's built-in cryptographic source and formats them on the spot. Nothing is sent to a server, nothing is logged, and there is no quota. Generate one UUID or fifty, as often as you like, and close the tab when you're done — nothing about your visit is retained.
Conclusion
Unique identifiers shouldn't require infrastructure. Pick a count, set your formatting preferences, and take a batch of standards-compliant version-4 UUIDs generated with proper cryptographic randomness. Paste them into your database, your import file, or your test suite, and get back to the actual work — the IDs will never collide.