UUID Generator
Generate random UUID v4 / GUID values in bulk, with optional uppercase and no-hyphen formatting.
How to use the UUID Generator
- Set how many UUIDs you need, anywhere from 1 to 100.
- Toggle Hyphens off if your system stores UUIDs as 32 bare hex characters, and Uppercase on if it expects capital letters.
- Press Generate, then use Copy all to grab the whole list, one UUID per line.
About the UUID Generator
A UUID (Universally Unique Identifier), also called a GUID, is a 128-bit value used to identify something — a database row, an API request, a session, a file — without needing a central authority to hand out sequential IDs. This tool generates version 4 UUIDs, the most common type, which are built from cryptographically random bits rather than a timestamp or hardware address.
Version 4 UUIDs are effectively collision-free in practice: the odds of two randomly generated UUIDs matching are so small they're not a practical concern, even across billions of values. Developers use them as primary keys, correlation IDs in logs, or unique filenames, without coordinating with any other system.
Worked example
Example: generating a UUID might produce 9b1deb4d-3b7d-4bad-9bdd-2b0d7b3dcb6d — the third group always starts with '4' (marking version 4), and the fourth group always starts with 8, 9, a, or b (marking the variant), per the UUID spec.
Anatomy of a version 4 UUID
A UUID is 128 bits written as 32 hexadecimal digits in groups of 8-4-4-4-12. In version 4, six of those bits are fixed: the first digit of the third group is always 4 (the version), and the first digit of the fourth group is always 8, 9, a, or b (the variant). The remaining 122 bits come from your browser's cryptographically secure random generator. You can generate up to 100 at a time.
Choosing a UUID version for databases
Random v4 UUIDs are ideal when you need IDs that reveal nothing and can be created anywhere. As database primary keys they have one drawback: because each new value is random, inserts land all over the index instead of at the end, which slows writes on very large tables. Version 7 UUIDs, standardized in 2024 (RFC 9562), start with a timestamp so new IDs sort in creation order — worth considering for high-volume tables. For most applications, v4 is perfectly fine.
Storage and formatting tips
- Store UUIDs in a native UUID column type (or 16-byte binary) where your database offers one; as text they take 36 characters.
- Compare UUIDs case-insensitively. The standard form is lowercase, but some systems output uppercase, and both mean the same value.
- Don't treat a UUID as a password or secret token. Even random UUIDs aren't designed as access credentials; use a dedicated token generator for that.
- If a system rejects the hyphenated form, use the no-hyphens option to get the plain 32-character string.
Frequently asked questions
- What's the difference between a UUID and a GUID?
- They're effectively the same thing. UUID (Universally Unique Identifier) is the name used in the formal RFC 4122 specification; GUID (Globally Unique Identifier) is Microsoft's term for the same 128-bit format. This tool generates standard RFC 4122 version 4 UUIDs, compatible with both names.
- Can two generated UUIDs ever collide?
- Theoretically yes, but practically no — a v4 UUID has 122 random bits, giving roughly 5.3 x 10^36 possible values. You'd need to generate around a billion UUIDs per second for about 85 years before there's a 50% chance of a single collision, so it's treated as effectively unique for real-world use.
- Are these UUIDs generated securely?
- Yes. This tool uses the Web Crypto API (crypto.getRandomValues), a cryptographically secure random number generator built into your browser, and everything runs locally — no UUID is sent to a server.
- When would I remove the hyphens or use uppercase?
- Some systems and legacy databases store UUIDs as a 32-character hex string without hyphens, or expect uppercase formatting (common in some Microsoft/.NET contexts). The hyphen and uppercase toggles let you match whichever format your target system expects.