How to use the UUID Generator tool
- Choose the versionVersion 4 is fully random. Version 7 starts with a timestamp, so IDs sort by creation time.
- Pick how many and the formatGenerate 1 to 1,000 UUIDs as lowercase, uppercase, without hyphens, in braces or as a JSON array.
- Copy or downloadCopy all UUIDs to the clipboard or download them as a text file.
- Validate (optional)Paste any UUID to check its format, version and variant.
Features
- Secure randomnessUses the browser’s cryptographically secure generator (crypto.randomUUID / getRandomValues).
- UUID v7 supportTime-ordered UUIDs from RFC 9562, ideal as database primary keys.
- Bulk generationUp to 1,000 UUIDs at once for test data, seed files and fixtures.
- Many formatsLowercase, uppercase, no hyphens, Microsoft-style braces or a ready-to-paste JSON array.
- ValidatorChecks a UUID and shows its version, variant and, for v7, the time it was created.
What is a UUID?
A UUID (Universally Unique Identifier), also called a GUID in the Microsoft world, is a 128-bit number used to identify things such as database records, files, devices, users and API requests. It is usually written as 32 hexadecimal digits in five groups separated by hyphens, for example 3f2b8c4e-9d1a-4c7e-8f6b-2a5d9e1c0b7a. UUIDs can be created independently on any computer without a central registry, while remaining practically unique.
Version 4 vs version 7
| UUID v4 | UUID v7 | |
|---|---|---|
| Made from | 122 random bits | 48-bit Unix timestamp (milliseconds) + random bits |
| Sort order | Random | Chronological (by creation time) |
| Reveals creation time | No | Yes, to the millisecond |
| Best for | Public tokens, IDs that should reveal nothing | Database primary keys, logs, event IDs |
Version 7 was standardized in RFC 9562 (2024). Because new v7 IDs are always larger than older ones, they are inserted at the end of database indexes, which keeps B-tree indexes compact and inserts fast. Random v4 keys are scattered across the index, which can slow down large tables.
How unique are UUIDs?
A version 4 UUID has 122 random bits, giving about 5.3 × 1036 possible values. You would need to generate roughly 2.7 × 1018 UUIDs before there is even a 50% chance of a single collision. In practice, a collision is far less likely than hardware failure, as long as a secure random number generator is used, like the one in your browser.
Reading the version and variant
The first digit of the third group is the version: xxxxxxxx-xxxx-4xxx-… for v4 and …-7xxx-… for v7. The first digit of the fourth group shows the variant; for standard UUIDs it is 8, 9, a or b. Paste any UUID into the validator above to decode these fields automatically.