UUID generator
Generate random version 4 UUIDs (GUIDs) instantly. Cryptographically secure. Bulk generation supported.
About the UUID
A UUID, or Universally Unique Identifier, is a 128-bit label used to identify information without a central coordinating authority. It is written as 32 hexadecimal digits split into five groups separated by hyphens — 8-4-4-4-12, as in 550e8400-e29b-41d4-a716-446655440000. The whole point of a UUID is that two parties can each generate one independently, with no shared database and no network connection, and be practically certain the values will never collide. That makes UUIDs the default choice for database primary keys, distributed systems, message identifiers, and any situation where an auto-incrementing number would force everything through a single bottleneck.
History of the UUID
UUIDs grew out of the Apollo Network Computing System in the 1980s and were later standardized as part of the Open Software Foundation's Distributed Computing Environment (DCE) in the early 1990s. The format was formally documented for the wider internet in RFC 4122 in 2005, which defined the five versions and the layout still in use today. Microsoft adopted the same 128-bit structure under the name GUID for its COM and Windows technologies, which is why the two terms describe identical values. In 2024, RFC 9562 refreshed the standard and added newer time-ordered versions such as UUIDv7, but the random version 4 remains the most widely generated.
Why version 4 UUIDs are used most
Of the several UUID versions, version 4 — the random UUID — is by far the most common in everyday software. It fills 122 of its 128 bits with random data and reserves the rest to mark the version and variant, so generating one needs nothing more than a good source of randomness. Unlike version 1, it does not embed a timestamp or the machine's MAC address, so it leaks no information about when or where it was created. That privacy, combined with the fact that any device can produce one offline, is why frameworks, databases and languages from PostgreSQL to Python default to version 4 when you ask for a UUID.
How this UUID generator works
Every UUID on this page is generated in your browser using the Web Crypto API's crypto.getRandomValues(), a cryptographically secure source of randomness, and never touches a server. The tool sets the version and variant bits exactly as RFC 4122 requires, so each result is a valid version 4 UUID. Formatting options — uppercase, removing hyphens, or wrapping the value in braces for Windows-style GUIDs — change only how the identifier is displayed, not the underlying 128-bit value. Use the count field to produce up to 100 at once, then copy an individual UUID or the whole batch.
Frequently asked questions
What is a UUID and how is it different from a GUID?
A UUID (Universally Unique Identifier) is a 128-bit value written as 32 hexadecimal digits in five hyphen-separated groups, such as 550e8400-e29b-41d4-a716-446655440000. GUID (Globally Unique Identifier) is Microsoft's name for the very same thing — the two terms are interchangeable, though GUID is more common in .NET and Windows contexts while UUID is standard everywhere else. Both follow the identical format and can be used wherever the other is expected, which is why this tool offers the uppercase and brace options often seen in Windows systems.
What is a version 4 UUID?
Version 4 is the random UUID: 122 of its 128 bits are filled with random data, while the remaining 6 bits are fixed to mark the version (the digit 4) and the variant. This tool generates version 4 UUIDs, the most widely used kind, because they need no central authority, no network access and no timestamp — just a good source of randomness. You can recognise a version 4 UUID by the digit 4 at the start of the third group and an 8, 9, a or b at the start of the fourth.
Are randomly generated UUIDs really unique?
Not mathematically guaranteed, but unique enough that collisions are effectively impossible in practice. With 122 random bits there are about 5.3 undecillion possible version 4 UUIDs. You would need to generate roughly 2.7 quintillion of them before there was even a one-in-a-billion chance of any two matching — more than any real system will ever create. For virtually every application, from database keys to session identifiers to file names, treating them as unique is completely safe.
Are these UUIDs safe to use as secrets or security tokens?
This generator uses the browser's cryptographically secure crypto.getRandomValues(), so the version 4 UUIDs produced here are unpredictable and generated entirely on your device. They are suitable as hard-to-guess identifiers such as password-reset links or invitation tokens. That said, a UUID carries only 122 bits of entropy and is designed as an identifier rather than a credential — for high-value secrets, a dedicated random token of appropriate length is still the better choice.
Why would I remove the hyphens or use uppercase UUIDs?
The hyphens are purely cosmetic — the canonical format includes them, but the 32 hex digits carry all the meaning, so removing them saves a few characters in URLs, filenames or compact database columns. Uppercase is common in Microsoft and Windows environments, where GUIDs are often displayed in capitals and wrapped in braces. Both options here change only the presentation; the underlying value is identical, so a hyphen-free lowercase UUID and its uppercase braced form refer to exactly the same identifier.