Most applications need identifiers that will not clash, even when two machines create records at the same time without asking a central database for the next integer. That is what a UUID is for: a 128-bit value you can generate independently.
The default choice is usually a random v4. The other versions exist for cases where you want time-ordering, or a value you can recreate from a name.
Versions this generator supports
The UUID Generator on ToolSphare follows RFC 4122 and can produce versions 1, 3, 4 and 5. The page itself summarises them:
- v1 — time-based, with a clock sequence and node
- v3 — name-based, using MD5
- v4 — random (most common)
- v5 — name-based, using SHA-1
For v3 and v5 you also choose a namespace — DNS, URL, OID, X.500 DN, or a custom UUID — and a name (the field defaults to example.com). The same name and namespace always yield the same v5 (or v3) identifier, which is the point: a stable ID for “this domain” or “this URL”, not a random one.
Formatting options:
- Uppercase letters (A–F)
- Include braces
{ } - Include hyphens
- Auto generate on load
A quantity stepper sits next to a Generate UUID button. The result panel shows the UUID, plus version, variant (RFC 4122), character count, a generated timestamp, and — for relevant versions — a timestamp field. You can copy or download a single value.
A second section, Bulk UUID Generator, asks how many to create (it defaults to 10), then Generate Bulk, with Copy All, Download .txt and Clear.
Generation is described as happening in the browser, with no registration.
How to use it
- Open the UUID Generator workspace.
- Pick a version. Use v4 unless you have a reason not to.
- For v3 or v5, set the namespace and the name. For v4 or v1 you can ignore those fields.
- Set formatting (hyphens on is the usual text form) and click Generate UUID, or set a bulk count and Generate Bulk.
- Copy the value into your fixture, schema or config. Do not hand-edit a character in the middle; generate a new one instead.
A practical example: test data versus a stable namespace ID
A developer in Islamabad needs 25 user IDs for a local demo database. Those IDs should be unique, but they do not need to mean anything. They choose v4, set the bulk count to 25, generate, and download the .txt list. Hyphens stay on, lowercase is fine, no braces, because that matches what their PostgreSQL uuid column expects.
Separately, a script needs a persistent ID for the site docs.example.com that any machine can recompute without a shared database row. That is a v5 job: namespace DNS, name docs.example.com. Running the generator twice with those inputs should produce the same UUID. If a third environment types www.docs.example.com instead, it will get a different ID — the name is part of the input.
Use v1 only if you understand that it encodes time (and, in classic v1, a node identifier). Many teams prefer v4 so IDs do not leak creation time in the obvious way.
What a UUID is not
It is not a secret. v4 IDs are hard to guess, but they are not authentication tokens and should not be treated as passwords. It is also not a substitute for a uniqueness constraint in your database; collisions are extremely unlikely for v4, but your schema should still describe the column as unique if that is the rule.
If a library or API asks for a “GUID”, it is usually the same 128-bit idea, sometimes printed with braces. Use the braces checkbox rather than adding { } by hand.
FAQ
Which version should I pick by default?
v4 (random). That is the one the tool’s own guide calls the most common.
Can I generate many at once?
Yes. The bulk section lets you choose a count, then copy or download a list as .txt.
Do I need an account?
No. The page describes the generator as free, running in the browser, with no sign-up.
Disclosure: I build ToolSphare, the free tools site that hosts the UUID generator described above.
