UUID Generator
Generate one or many random UUID v4 strings, with options for case and dashes.
What a UUID v4 looks like
Every UUID has 36 characters: 32 hexadecimal digits (0–9, a–f) in five groups of 8, 4, 4, 4 and 12, separated by dashes. Two digits have a fixed meaning:
- The first digit of the third group is always 4. It is the version: version 4 means the UUID is made from random numbers.
- The first digit of the fourth group (y) is always 8, 9, a or b. It is the variant, and marks the standard layout from RFC 9562 (formerly RFC 4122).
- All other 122 bits are random.
Without dashes, the same UUID is a 32-character string, for example 3f2b8c1e9d4a4e7ba1c25f6e7d8c9b0a.
When to use a UUID
Use a UUID when you need an ID that is unique everywhere, not just inside one database table. Typical uses are primary keys in distributed databases, IDs that apps create offline before they sync, file and upload names, request and trace IDs in logs, and idempotency keys for payment APIs.
Random v4 UUIDs are not sorted by time. If you use them as the primary key of a very large table, a time-ordered UUID (version 7) can make inserts faster. For most apps, v4 is the simple and safe default.
Frequently asked questions
What is a UUID?
A UUID (universally unique identifier) is a 128-bit number used to label things like database rows, files, API requests or devices. It is written as 32 hexadecimal digits in five groups, for example 3f2b8c1e-9d4a-4e7b-a1c2-5f6e7d8c9b0a. Anyone can create one without asking a central server, and it will still be unique in practice.
What is the difference between a UUID and a GUID?
There is no real difference. GUID (globally unique identifier) is the name Microsoft uses, for example in Windows, .NET and SQL Server. The format is the same, so the UUIDs from this page work anywhere a GUID is expected.
Can two UUID v4 values ever be the same?
In theory yes, in practice no. A version 4 UUID has 122 random bits. You would need to create about 2.7 quintillion (2.7 × 10^18) UUIDs before there is even a 50% chance that two of them match.
Are these UUIDs safe to use?
Yes. They are made in your browser with the Web Crypto API (crypto.randomUUID), which uses a cryptographically secure random number generator. Nothing is sent to a server and nothing is stored, so no one else sees your UUIDs.
Should I use uppercase or lowercase, with or without dashes?
The standard form is lowercase with dashes, and most systems expect that. UUIDs are not case-sensitive, so uppercase means the same value; some Windows tools show GUIDs in uppercase. Remove the dashes only when a system needs a plain 32-character string.
How many UUIDs can I generate at once?
Up to 100 per click. Click Generate again for a new batch, then Copy All to copy them, one per line.