iLoveDevToolWhen you need a UUID generator
Faking primary keys for test data, choosing a key type for a new table, tagging events in a stream, or passing an identifier between distributed services without a central issuer — the common thread is you need a string that will practically never collide, and you need it now.
UUIDs are the standard answer: 128 bits, well specified (RFC 4122, and RFC 9562 in 2024), generatable from the standard library of almost every language. The value of an online generator is grabbing a batch without writing code — and switching formats to match whatever system you're pasting into.
v4 or v7: the one-line rule
- v4: 122 bits of cryptographically secure randomness. The UUID you see in databases, legacy systems, and other people's frameworks is v4 nine times out of ten. When unsure, use it.
- v7: a 48-bit millisecond Unix timestamp prefix plus random bits. It's time-ordered — MySQL/PostgreSQL primary-key indexes append instead of scattering, and event IDs sort naturally. Worth preferring in new projects.
A detail worth knowing: the first 48 bits of a v7 are the millisecond timestamp. Read the first 12 hex characters of a v7 as an integer and you get the moment it was created — check it with a Unix timestamp converter.
iLoveDevTool's online UUID generator
Our online UUID generator keeps the common needs direct:
- Three versions — v4, v7, and nil: v7 values increase strictly within the same millisecond, so a batch doubles as ordered test data;
- Up to 1000 at once: copy the whole batch as newline-separated text or a JSON array, ready to paste into test code;
- Formats on toggles: uppercase, no hyphens, and braces (GUID style) — one switch each for Windows, Java, and PostgreSQL conventions;
- Fully local: randomness comes from the browser's secure crypto API; nothing is uploaded.
How it compares with uuidgenerator.org
uuidgenerator.org is the most established site in this category — worth respecting, and worth comparing honestly:
| Dimension | uuidgenerator.org | iLoveDevTool |
|---|---|---|
| Versions | single format (unlabeled) | explicit v4 / v7 / nil |
| Bulk | one at a time | 1 to 1000 in one batch |
| Format options | fixed lowercase-hyphenated | uppercase / hyphens / braces toggles |
| Interface | English | 20 languages, Chinese-first |
| Track record | a decade of mind share, evergreen in search | a newer tool that wins on leanness and speed |
The old site's edge is "search and you'll find it" mind share; on features, our generator covers more across versions, bulk, and formats.
Frequently Asked Questions
Is uuidgenerator.org free to use?
Yes. uuidgenerator.org's generator is free and requires no sign-up. Its interface is English-only with basic bulk and formatting options; iLoveDevTool's UUID generator is also free and adds v7, batches of up to 1000, uppercase/hyphen/braces format toggles, and 20 interface languages.
Should I use UUID v4 or v7?
When unsure, use v4 — it is the default in most databases and frameworks and has the best compatibility. v7 starts with a 48-bit millisecond timestamp, so it is time-ordered: primary-key indexes don't scatter, and logs and event streams sort naturally. New tables and event IDs are where v7 shines. Existing v4 systems don't need migrating.
Are GUIDs and UUIDs the same thing?
Yes. GUID is Microsoft's name for a UUID; the two have been equivalent since RFC 4122. The braced uppercase style common in the Windows ecosystem is just a formatting variant — toggling the uppercase and braces options in a generator produces it.