Test fixture keys
Generate five version 4 UUIDs and download the JSON array to populate a small fixture file.
Choose an identifier
122 random bits with fixed version and variant bits.
Export format
Example shape: 00000000-0000-4000-8000-000000000000. Generate fresh values for actual use.
Randomness comes from Web Crypto. Values exist in page memory until cleared or the page closes.
Generated values remain in page memory until cleared or the page closes. They are not added to browser storage or the URL.
How to use the UUID Generator
- 01
Choose version 4 for a random layout or version 7 for an embedded millisecond timestamp.
- 02
Enter a batch size from 1 to 500 and select Generate UUIDs.
- 03
Choose the display case and export format, then copy or download the generated batch.
Examples
Time-oriented records
Choose version 7 when an application expects the RFC 9562 version 7 layout. The first 48 bits hold the batch’s generation time.
A format example is not a fresh ID
00000000-0000-4000-8000-000000000000 illustrates the version and variant positions. Do not reuse it as a newly generated unique key.
Version and variant fields
A UUID is a 128-bit value displayed here as 32 hexadecimal digits and four hyphens. Fixed version and variant bits identify the layout. Version 4 leaves 122 random bits; version 7 reserves 48 bits for Unix milliseconds and leaves 74 random bits in this implementation.
Ordering and timestamp disclosure
Version 7 values generated at different timestamps sort by their timestamp prefix. All IDs in one batch share one timestamp, and their remaining bits are sampled independently. There is no counter or monotonic guarantee within the same millisecond. System clock changes can also affect ordering.
Uniqueness and purpose
Web Crypto supplies the random bytes; Math.random is not used. The chance of collisions is small, not mathematically zero. Keep database uniqueness constraints where collisions matter. UUIDs are identifiers, and this generator does not promise suitability as authentication secrets.
What to know
- Supports UUIDv4 and UUIDv7 only. Version 7 is random within a millisecond and is not monotonic.
Common questions
Are uppercase UUIDs different IDs?
No. Uppercase changes the hexadecimal presentation. The underlying 128-bit value is the same.
Does version 7 hide creation time?
No. Its timestamp is readable by design. Choose an identifier strategy appropriate to the information you can disclose.
Are these guaranteed unique across every system?
No. Independent random generation provides probabilistic uniqueness, so applications should still enforce their own constraints.