UUID Generator
Create random v4 or time-ordered v7 UUIDs with a cryptographically secure generator, and copy them all with one click.
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Copy the code and paste it into your page's HTML. It's free; please keep the credit link.
How these UUIDs are made
Both versions come from crypto.getRandomValues, the browser's cryptographically secure random number generator. Version 7 replaces the first 48 bits with the current Unix time in milliseconds. In both, 4 bits mark the version and 2 bits the variant, exactly as RFC 9562 (2024, which replaced RFC 4122) specifies.
v4 or v7?
| UUID v4 | UUID v7 | |
|---|---|---|
| Made from | 122 random bits | Millisecond Unix time + 74 random bits |
| Sort order | Random | Order of creation |
| Database index | Inserts land all over the index | New rows go at the end, like an auto-increment ID |
| Reveals | Nothing | When it was created |
Frequently asked questions
Can two UUIDs ever be the same?
In theory yes, in practice no. A v4 UUID has 122 random bits; you'd need about 2.7 quintillion (2.7 × 10¹⁸) of them for a 50% chance of a single duplicate.
Should I use UUID v4 or v7 for database keys?
v7 is usually better for primary keys. It starts with a timestamp, so new rows go to the end of the index, as with auto-increment IDs, which keeps inserts fast. Use v4 when the ID shouldn't reveal when it was created.
What's the difference between a UUID and a GUID?
None in practice. GUID is Microsoft's name for the same 128-bit identifier, often written uppercase and in braces, such as {3F2504E0-4F89-41D3-9A0C-0305E82C3301}.
Is what I paste sent to a server?
No. This tool runs entirely in your browser with JavaScript and the built-in Web Crypto API. Nothing you type, paste or open is uploaded or stored.