A Universally Unique Identifier (UUID), also called a GUID, is a 128-bit value shown as 32 hexadecimal characters in five dash-separated groups. It is designed so that any machine can generate a UUID without coordinating with any other machine and the chance of a collision stays effectively zero.

What is the difference between UUID v1 and v4?

Version 1 uses the current timestamp and a MAC-like node id to build the UUID, which means two UUIDs generated on the same machine are sortable by time. Version 4 is purely random and does not leak timing or hardware information, which makes it the common choice for public identifiers.

Are v4 UUIDs truly unique?

Not strictly, but the probability of a collision is so low it is practically ignored. You could generate one billion UUIDs per second for 85 years and still have less than a 50 percent chance of a single duplicate.

Can I use UUIDs as database primary keys?

Yes. Many modern systems do. The trade-off is that v4 UUIDs are random and can fragment B-tree indexes, which is why newer databases offer v7 UUIDs that stay roughly sortable by time while remaining collision-safe.

Is this generator cryptographically secure?

Yes. v4 UUIDs on this page use the browser crypto.getRandomValues API, which draws from the operating system CSPRNG.

Can I bulk-generate UUIDs?

Yes. Pick a quantity up to 500 and the tool will output one per line, ready to copy or paste into a seed script.

UUID Generator: Create v4, v1 and NIL UUIDs Online (Free)

What is a UUID

A Universally Unique Identifier (UUID), also called a GUID in the Microsoft world, is a 128 bit value that can be created independently on any machine with a vanishingly small chance of collision with any other UUID generated anywhere else. The format is written as 32 hexadecimal digits in five dash separated groups of 8-4-4-4-12, for example 4d97f0bd-7c47-4a4b-99b8-3c02c56f9a14. UUIDs are defined by RFC 4122 from the IETF and are implemented natively in every mainstream language and database.

Which Version Should I Use

Most new systems should default to version 4. These UUIDs are generated from 122 bits of cryptographically secure random data and leak no information about when or where they were created. They are the right choice for public URLs, API request ids, shopping cart ids, idempotency keys and anything that should not be guessable or orderable by an outsider.

Version 1 UUIDs embed the current timestamp and a node identifier. That makes them sortable by creation time and useful for internal systems that want to cluster rows created close together in a database index. The downside is that the timestamp and node id are readable from the UUID, which can leak information.

The NIL UUID, 00000000-0000-0000-0000-000000000000, is a special sentinel. Use it where you need to represent an unset or placeholder value, similar to NULL. Never treat it as a real identity.

How to Use This Tool

Pick the UUID version you need. Default is v4 which fits most use cases.
Enter the quantity. Up to 500 UUIDs can be generated in a single batch.
Optionally change the letter case, remove dashes or wrap each UUID in braces for languages that expect that style.
Press Generate and the output appears in the dark box below. Use Copy all to send the entire batch to the clipboard.

Common Use Cases

Database primary keys: especially when records are created across multiple nodes that cannot coordinate on an auto-increment counter.
Idempotency keys: prevent a payment or signup being processed twice when the client retries a request.
File and asset names: uploaded files are renamed to a UUID to prevent collisions and to hide the original filename.
Correlation ids: stamp every log line of a request with the same UUID so traces can be reconstructed across services.
Test data: seed a database with repeatable fixture rows using pre-generated UUIDs.

UUIDs are not secrets A UUID is unique but it is not a password. Do not use one as an access token. Anyone who learns the UUID of a record can address that record.

UUID v4 vs v7

RFC 9562, published in 2024, adds versions 6, 7 and 8 to the UUID family. Version 7 embeds a millisecond Unix timestamp in the high bits and random bits in the rest. The result is a UUID that is still collision-safe but also sortable by time, which plays much better with database B-tree indexes than fully random v4. Many new systems built in 2025 and 2026 default to v7. This generator focuses on the long-standing v1 and v4 since they are the formats most libraries and existing databases expect today.

Privacy

Everything on this page runs in your browser. No UUID is sent to or logged by any server. You can even disconnect from the internet after the first page load and keep generating identifiers.

Frequently Asked Questions

What is a UUID?

A 128 bit identifier shown as 32 hex characters in 8-4-4-4-12 form, standardized by RFC 4122.

What is the difference between v1 and v4?

v1 encodes a timestamp and node id and is sortable by time. v4 is random and leaks nothing about the issuer.

Are UUIDs really unique?

Practically yes. The collision probability is small enough to ignore even at planet scale.

Can I use UUIDs as database keys?

Yes. For heavy write workloads consider UUID v7 for better index locality.

Is the generator cryptographically secure?

Yes. v4 UUIDs use the browser CSPRNG via crypto.getRandomValues.

What is the NIL UUID?

The all-zero value used as a placeholder.

Can I bulk generate?

Yes, up to 500 at a time.