UUID Generator
Generate v4 UUIDs in bulk.
Output will appear here.
What is a UUID Generator?
A version 4 UUID is a 128-bit value of which 122 bits are random, written as 36 characters in five hyphen-separated groups. Six bits are fixed to mark the version and variant, which is why the third group always starts with 4.
Because they are random rather than assigned, two systems can mint UUIDs independently and never coordinate. The chance of a collision is negligible: you would need to generate billions of them before a duplicate became likely at all. That property is what makes UUIDs the default identifier for distributed systems, offline-first clients and anything where a database sequence would be a bottleneck.
The trade-off is locality. Random UUIDs scatter across a B-tree index, which hurts insert performance and index size at scale. When that matters, a time-ordered identifier such as UUID v7 or ULID keeps global uniqueness while restoring ordering.
When you need it
- Primary keys that a client can generate before it ever reaches the server.
- Correlation and request IDs that stay unique across services.
- Idempotency keys for a payment or job submission.
- Test fixtures and seed data that must not collide.
- Filenames or object-storage keys for uploads.
How to use the UUID Generator
- Set how many you need — anything from 1 to 1000.
- Choose uppercase output, or drop the hyphens, if the target system expects that form.
- Press Generate. Each press produces a fresh batch, so the list never shifts while you are copying from it.
- Copy all of them, or download the batch as a text file.
Examples
UUID Generator features
Frequently asked questions
Are these UUIDs really random?
Yes. They come from crypto.randomUUID(), or from crypto.getRandomValues() where that is unavailable — both are cryptographically secure generators provided by the browser, not Math.random().
Could two of these ever collide?
In practice, no. With 122 random bits you would need on the order of a billion billion UUIDs before a collision became probable. Hardware failure is far likelier.
Should I use a UUID as a database primary key?
It works and is common, but random UUIDs scatter writes across the index, which costs insert throughput and space at high volume. If that matters, use a time-ordered UUID v7 or store the value as a 16-byte binary rather than a 36-character string.
What is the difference between a UUID and a GUID?
None, in practice. GUID is Microsoft’s name for the same 128-bit identifier. GUIDs are often written in braces and uppercase, which is a formatting difference only.
Is a UUID a secret?
A v4 UUID is unguessable, so it can act as a capability token — an unlisted share link, for instance. But it never expires and cannot be revoked on its own, so it is not a substitute for real authentication.
Is my data uploaded to a server?
No. Every iZZi DevTools tool runs inside your browser using the standard web platform. The data you paste is processed on your own machine and is never transmitted, stored or logged by us.
Do I need an account?
No. Every core tool is free, unlimited and works without signing in. An account only adds conveniences such as saved snippets and history.
Does it work offline?
Once the page has loaded, yes. Because the processing happens in the browser rather than on a server, the tool keeps working if your connection drops.