UUID Generator
Generate v4 UUIDs in bulk.
UUID Generator at a glance
UUID Generator is a free online developer tool you can use right now to generate v4 UUIDs in bulk โ no account, no install and no usage limit. It runs entirely inside your browser, so whatever you enter stays on your own device.
- Price
- Free โ no trial, no paid tier, no watermark
- Sign-up
- Not required
- Where it runs
- In your browser โ nothing is uploaded to a server
- Works on
- Chrome, Safari, Firefox and Edge โ desktop, tablet and phone
- Category
- Developer Tools
About UUID Generator
A UUID is a 128-bit identifier written as 32 hexadecimal digits in five hyphen-separated groups. This generator produces version 4 UUIDs, the variant whose bits are random rather than derived from a timestamp or hardware address, and it can produce them in bulk for seeding a database or building test fixtures.
The appeal of UUIDs is that they can be generated independently anywhere โ on a client, on several servers, offline โ without coordination, and still not collide. Version 4 has 122 random bits. The collision probability is small enough that you would need to generate billions of UUIDs before it became worth thinking about, which is why distributed systems rely on them where a database's auto-incrementing integer cannot work.
Randomness quality is the part that matters and is easy to get wrong. These are generated with the Web Crypto API, the browser's cryptographically secure random source. Many naive implementations use Math.random(), which is not cryptographically secure and can produce predictable sequences โ fine for a shuffle, genuinely dangerous for anything acting as an unguessable identifier such as a password-reset token or a share link.
One practical caution before using UUIDs as primary keys: they are random, so inserting them into a clustered index writes to scattered points in the index rather than appending at the end. On large tables this causes page splits and measurably slower inserts. Many teams use a UUID as a public-facing identifier alongside an internal sequential key.
How to use UUID Generator
- Choose how many UUIDs you need.
- They are generated instantly using your browser's cryptographic random source.
- Copy one or the whole list to your clipboard.
Frequently asked questions
What does version 4 mean?
It is the variant whose bits are randomly generated, as opposed to version 1 which embeds a timestamp and MAC address. Version 4 leaks no information about when or where it was created, which is why it is the usual default.
Could two UUIDs ever be the same?
In principle yes, in practice no. Version 4 has 122 random bits, so you would need to generate on the order of a billion UUIDs per second for decades before a collision became probable. It is not a risk worth engineering around.
Are these random enough for security tokens?
They come from the Web Crypto API, the same cryptographically secure source used for real key generation โ not Math.random(). That makes them suitable for unguessable identifiers. For actual secrets such as session tokens, prefer a dedicated token generator with a documented length.
Should I use a UUID as a database primary key?
It depends on the table. UUIDs distribute randomly across a clustered index, which causes page splits and slower inserts at scale. A common pattern is an internal auto-incrementing key for storage plus a UUID as the public identifier, which avoids exposing row counts.