UUID Generator
Generate random RFC-4122 version-4 UUIDs (also called GUIDs) in your browser. Choose how many you need, toggle uppercase or hyphens, and copy the results instantly — nothing is uploaded.
Options
Quantity
Uppercase
Hyphens
How to use UUID Generator
- 1
Set the quantity
Choose how many UUIDs you need, from 1 up to 100, using the quantity field or the plus and minus buttons.
- 2
Choose the format
Toggle Uppercase for capital hexadecimal letters and toggle Hyphens to keep or strip the four dashes from each ID.
- 3
Generate the IDs
Click Generate to create cryptographically random version-4 UUIDs, each listed on its own line.
- 4
Copy the results
Use the Copy button to copy the whole list at once, ready to paste into code, a database, or a spreadsheet.
UUIDs in Depth: Versions, Collisions, and When to Use Them
What a UUID is
A UUID — Universally Unique Identifier, called a GUID in the Microsoft world — is a 128-bit value designed to be unique without any central authority handing out numbers. Its canonical text form is 36 characters: 32 hexadecimal digits split into five groups by four hyphens, in an 8-4-4-4-12 pattern. Those 128 bits are the whole identity; the hyphens and letter case are just presentation.
The promise is decentralization. Any machine, anywhere, can mint an identifier with effectively no chance of clashing with one minted elsewhere, which is why UUIDs are the default key when independent systems must generate IDs that later merge without coordination.
Version 4: random by design
This generator produces version-4 UUIDs, the most widely used kind. A v4 UUID is almost entirely random: of the 128 bits, a handful are fixed to mark the version and variant, leaving 122 bits of pure randomness. You can spot a v4 value because the digit that opens the third group is always a 4, and the digit opening the fourth group is one of 8, 9, a, or b.
Because there is no embedded timestamp or machine identifier, a v4 UUID leaks nothing about when or where it was created. That privacy is a genuine advantage over schemes that encode a MAC address or a sequence, and it is part of why v4 became the everyday default for keys, tokens, and record identifiers.
How the randomness is sourced
Quality of the random source is everything for a random UUID. This tool uses your browser's built-in cryptographically secure generator — the same primitive used for security-sensitive values — rather than a fast but predictable pseudo-random function. That matters because IDs produced from a weak generator can be guessed or enumerated, turning an identifier that was supposed to be unguessable into a security hole.
With a proper cryptographic source, the 122 random bits are genuinely unpredictable, so the output is suitable for production database keys, idempotency keys, and similar uses. It is worth stressing the boundary, though: a UUID is an identifier, not a secret. Treat it as unguessable-enough to be hard to enumerate, but do not rely on it alone as an authorization token.
Why collisions are not a practical worry
The space of v4 UUIDs is astronomically large — 2 to the 122nd power, roughly 5.3 times 10 to the 36th distinct values. To put that in perspective, you would have to generate billions of UUIDs per second for many decades before the probability of a single collision rose to anything measurable. For every realistic application the chance of two randomly generated v4 UUIDs matching is so small it is treated as zero.
This is why you can generate IDs independently on thousands of clients and servers and simply assume they will not collide, without a uniqueness check round-trip to a central service. The improbability is the feature: it buys you coordination-free generation at the cost of nothing you will ever observe in practice.
Version 1, version 7, and sortability
Not all UUIDs are random. Version 1 derives its value from the current time and the generating machine's network address, which guarantees uniqueness but bakes a timestamp and a hardware identifier into the ID — a privacy and information-leak concern that pushed many teams toward v4. Version 7 is the modern answer to a different problem: it places a millisecond timestamp in the high bits followed by random bits.
That layout makes v7 values sort in roughly creation order as plain strings, which is a real benefit for database indexes. Purely random v4 keys scatter across an index and can hurt insert performance on some engines, whereas time-ordered keys keep recent inserts grouped. If you need the global-uniqueness story of a UUID but also want chronological ordering, v7 is the one to reach for; if you specifically want no embedded time, v4 remains the right choice.
UUIDs versus auto-increment IDs
The classic alternative is a database auto-increment integer. Sequential integers are compact, naturally ordered, and trivially efficient as primary keys, but they require a single source of truth to hand out the next number and they expose information: a sequential ID reveals roughly how many records exist and lets an attacker guess neighboring IDs by adding one. UUIDs solve both problems — no central counter, and no enumerable sequence.
The trade-offs run the other way too. A UUID is 16 bytes versus a 4- or 8-byte integer, its text form is bulky in URLs and logs, and a random one is not sortable. A reasonable rule of thumb: use UUIDs when IDs must be generated by clients or distributed services, must merge across systems, or must not be guessable; stick with auto-increment integers for a single self-contained database where compactness and ordering matter most.
Formatting and bulk generation
The canonical form is lowercase hex with hyphens, and most systems accept it, but conventions vary. This tool lets you switch to uppercase letters, which some platforms and older Microsoft tooling prefer, and to strip the hyphens for a compact 32-character form that is handy in URLs, filenames, or anywhere the dashes are noise. The underlying 128-bit value is identical regardless of case or hyphenation, so these are purely display choices.
When you need many IDs at once — seeding a table, generating test fixtures, pre-allocating keys — you can produce a batch in a single click and copy the whole list together, each on its own line. Everything is generated locally in your browser and nothing is transmitted or stored, so even identifiers tied to sensitive records never leave your device.
Frequently asked questions
What kind of UUIDs does this generate?
How are the random values produced?
How many UUIDs can I create at once?
Are the generated UUIDs really unique?
Is anything sent to a server?
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