UUID / GUID Generator

How to use 3 steps

Set the Quantity.
Press Generate UUIDs.
Press Copy UUID List.

Quantity (1 - 20):

Generated UUID v4 List

How this tool works

A UUID is a 128-bit identifier written as thirty-two hexadecimal characters in five hyphenated groups. The version generated here is version 4, which is very nearly all random: no counter, no timestamp, no machine identifier, so two systems that have never communicated can each mint identifiers without any risk of collision worth planning for.

Randomness comes from the browser's cryptographic generator rather than from Math.random, which matters because Math.random is not unpredictable and identifiers derived from it can be guessed. Up to twenty are produced at a time.

Where UUIDs help and where they cost

Collisions are not a practical concern: the space is large enough that generating billions of version 4 UUIDs leaves the chance of a repeat negligible. You do not need to check for duplicates.
They are not secret: a UUID identifies something, it does not protect it. An unguessable identifier is not an access control, and anything reachable by URL alone needs a real permission check.
They are poor primary keys in some databases: random values scatter writes across an index rather than appending to it, which fragments the index. Where that matters, a time-ordered variant is the usual answer.
Case and hyphens are presentational: the same identifier may appear upper or lower case, with hyphens or without. Normalise before comparing, or matching will fail on identical values.

What version 4 actually is

A UUID is a 128-bit identifier written as thirty-two hexadecimal characters in five hyphenated groups, and the [msm_tool slug="uuid-generator"] produces version 4, which is very nearly all randomness — no counter, no timestamp, no machine identifier embedded anywhere inside it. That is precisely what lets two systems that have never communicated with each other mint identifiers independently with no coordination and no meaningful risk of collision.

Collisions are not worth planning around

The space a version 4 UUID is drawn from is large enough that generating billions of them leaves the chance of a repeat vanishingly small — small enough that checking for duplicates before use is not a step any application actually needs to take.

They identify, they do not protect

A UUID makes something addressable; it does not make it secure. An identifier being difficult to guess is not the same thing as an access control, and anything reachable purely by knowing its UUID still needs a real permission check behind it — treating an unguessable URL as sufficient protection on its own is a mistake worth avoiding deliberately.

Where they cost you: database performance

Random values scatter writes across an index rather than appending to its end in order, which fragments the index over time in a way a sequential or time-ordered key does not. Where write performance genuinely matters, a time-ordered identifier variant is the usual fix, rather than abandoning UUIDs altogether.

Case and hyphenation are presentation only

The same identifier can legitimately appear in upper or lower case, with hyphens or without, and both forms represent exactly the same value. Comparing two UUIDs without normalising case and formatting first is a common way for identical values to be treated as different simply because they were written down differently.

Where the randomness actually comes from

Generation draws on the browser's cryptographic random number source rather than `Math.random`, which matters because `Math.random` is not built to be unpredictable and identifiers derived from it can, in principle, be guessed. Up to twenty identifiers are produced in a single run.

Frequently Asked Questions

Specific to the UUID / GUID Generator. Broader questions about this category are answered on the category page.

Could two UUIDs ever be the same?

In theory. In practice the space is so large that the chance is negligible even across billions of them, and no application needs to check.

Are UUIDs secure enough to use as tokens?

No. They identify, they do not authorise. Anything protected only by an unguessable URL is not protected.

What version does this generate?

Version 4, which is essentially random. It carries no timestamp, machine identifier or counter.

Are they safe to use as database keys?

They work, but random values scatter index writes and can fragment the index. Where write performance matters, a time-ordered identifier is better.

Does uppercase matter?

No. Case and hyphenation are presentation only, but normalise before comparing or two identical identifiers will not match.