UUID Generator

Use UUID Generator

Version 4 UUIDs generated on this device using browser cryptography. Collisions are extremely unlikely, not impossible; keep uniqueness checks in your application.

How many

Randomness, not a sequenceA version 4 UUID is 122 random bits. There is no counter and no ordering, so two of them say nothing about which came first - use a timestamp if you need that.

Identifiers

Generating identifiers on this device...

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About UUID Generator

Generate random version 4 UUIDs for test records, request tracing and application identifiers. Each result is 36 characters: 32 hexadecimal digits separated by four hyphens in an 8-4-4-4-12 layout. The tool creates five identifiers when it opens; choose a batch size from 1 to 1000 and press Generate to replace them. Copy all places one UUID per line on your clipboard, with no JSON array or SQL syntax added. Generation uses your browser's cryptographic random source, not identifiers fetched from a server. Independent systems can generate v4 UUIDs without coordinating a counter, but randomness makes collisions extremely unlikely rather than impossible. Keep database uniqueness checks and handle conflicts in production.

Generate and copy identifiers

Each identifier is a version 4 UUID: 122 random bits, plus six fixed bits marking the version and variant so other software can recognise the format. Those fixed bits are why every UUID here has a 4 at the start of the third group.
Randomness comes from crypto.randomUUID when available, or crypto.getRandomValues with the version and variant bits applied. UUID generation itself does not send the identifiers to a server; copying or pasting them elsewhere is a separate action.
Ask for as many as you need, up to a thousand at once, and copy the lot in a single action. Bulk generation is the common case when seeding a database or writing fixtures, and copying them one at a time is tedious.
Press generate again for an entirely new set. There is no seed and no sequence, so nothing carries over between batches.

Ways to use UUID Generator

Seeding test data

Generate a hundred at once and paste them straight into fixtures or a seed script, rather than writing a loop to produce them.

A correlation ID for tracing

A single UUID attached to a request lets you follow it across services in logs, without revealing anything about the request itself.

Recognise the UUID layout

The illustrative value 550e8400-e29b-41d4-a716-446655440000 has five groups with lengths 8, 4, 4, 4 and 12. The third group starts with 4 for version 4; the fourth starts with 8, 9, a or b for the variant. Do not reuse this published example as a fresh identifier.

Identifier format and limitations

Version 4 UUIDs carry no order. They are pure randomness, so you cannot sort by them to get creation order, and inserting them as a primary key in a clustered index causes scattered writes and page splits. Databases under write pressure often prefer a time-ordered identifier for exactly this reason.
Collisions are not impossible, merely negligible. With 122 random bits you would need to generate billions per second for a very long time before a repeat became likely. Treat them as unique in practice, but do not remove a uniqueness constraint from your database on the strength of it.
A UUID is an identifier, not a secret. It is unguessable enough to be hard to enumerate, which is why unlisted links use them, but anyone who sees one can reuse it. Do not treat possession of a UUID as authentication.
Formatting varies between systems. Some expect uppercase, some strip the hyphens, and Microsoft tooling often wraps them in braces. These are lowercase and hyphenated, the form specified by the standard; convert if your target demands otherwise.

Questions about UUID Generator

Are these requested from a server?

No. They are produced in your browser. No network request is made when you generate, and the identifiers exist only in this tab until you copy them.

Is a UUID the same as a GUID?

In practice yes. GUID is the name Microsoft uses for the same 128-bit identifier. Tooling in that ecosystem often displays them in uppercase or inside braces, but the value is the same.

What makes it version 4?

The bits are random rather than derived from a timestamp or hardware address. The version digit is fixed to 4 and two variant bits are set, which is why those positions never look random.

Should I use one as a database primary key?

It works, but random keys scatter writes across an index and can hurt insert performance at scale. Many teams use a time-ordered identifier for the key and keep a UUID as the externally visible reference.

Could I ever get the same one twice?

A repeat is possible, although the probability is extremely small with a functioning cryptographic random source. The page does not compare a new value against every UUID ever generated. Enforce uniqueness in storage and retry a conflicting insert instead of treating generation as an absolute guarantee.