What is the difference between UUID v1 and v4?

Version 1 is generated from a timestamp and a node identifier, so it encodes creation time and sorts roughly in order. Version 4 is random, making it unguessable but unordered. Use v4 when you don't want IDs to leak timing; use v1 when sortability matters.

Are UUIDs guaranteed to be unique?

They are not strictly guaranteed, but the probability of a collision is so small it's effectively negligible for practical use. A v4 UUID has 122 random bits, so generating them independently across many machines is safe without coordination.

How do I validate that a string is a real UUID?

Paste it into the validator. The tool checks that it matches the canonical 8-4-4-4-12 hexadecimal format and reports the version. An invalid result usually means a wrong length, a non-hex character, or missing hyphens.

Should I use a UUID as a database primary key?

You can, and it avoids coordinating ID generation across services. Be aware that random v4 keys spread inserts across the index, which can hurt write locality; time-ordered identifiers cluster better. Choose based on your database and access patterns.

Are the generated UUIDs sent to a server?

No. Generation, validation, and timestamp inspection all run in your browser, so no identifier is ever transmitted or logged.

UUID Generator & Validator

Generate v1 or v4 UUIDs, validate existing ones, detect versions, and inspect v1 timestamps. Use the tabs below to generate or inspect UUIDs.

Generation Options

Version

Count

Prefix

Suffix

Uppercase

About UUID Generator & Validator

A UUID is a 128-bit identifier you can generate anywhere — on any server, in any process, offline — with near-zero risk of two of them ever colliding. That property makes them the default choice for database primary keys, distributed system identifiers, idempotency keys, and anything that needs to be unique without a central authority handing out numbers.

The two versions you'll meet most often behave very differently. Version 4 is purely random, which makes it unguessable and ideal when you don't want IDs to leak ordering or timing. Version 1 is built from a timestamp and a node identifier, so it's sortable and carries the creation time — which this tool can extract and show you. Picking the right one matters: random UUIDs scatter across a database index, while time-based ones cluster.

This generator creates v1 or v4 UUIDs on demand and also works in reverse: paste an existing UUID to confirm it's well-formed, detect which version it is, and — for v1 — decode the embedded timestamp. Everything runs locally, so generated IDs are never logged or transmitted.

How to use UUID Generator & Validator

Pick a version
Choose v4 for random, unguessable identifiers, or v1 when you want the ID to encode its creation time and sort roughly in order.
Generate
Produce one or many UUIDs at once and copy them straight into your seed data, code, or test fixtures.
Validate an existing UUID
Paste a UUID to confirm it follows the correct 8-4-4-4-12 format and to detect which version it belongs to.
Inspect a v1 timestamp
For version 1 UUIDs, the tool decodes the embedded timestamp so you can see when the identifier was created.

Frequently asked questions

CUID & CUID2 Generator

Generate collision1 -resistant unique identifiers (CUID vand CUID2) instantly.

Hash Generator & Verifier

Generate MD5, SHA-1, SHA-256, SHA-512, and bcrypt hashes. Verify strings against known hashes.

Timestamp Converter

Convert Unix timestamps (seconds/ms), ISO 8601 strings, and human-readable dates. View local time, relative time, and next cron times.