A typical UUID v4
Random id
550e8400-e29b-41d4-a716-446655440000
Five hex groups separated by hyphens. The 4 in position 13 indicates this is a version 4 (random) UUID.
UUID Generator
Generate v1/v4 UUIDs in bulk, copy-ready.
Last updated
10 UUIDs
ResultV4
Runs in your browser using window.crypto- 1
fb6f57bd-8c7c-4fb8-a589-ddc01db8d610 - 2
4c9f7b35-29ec-4d3b-96da-c2086b1aad33 - 3
078091c4-24fe-4d6c-8a55-073f7ba0d468 - 4
79ff2c79-f371-41ac-acf5-21263f0724fe - 5
21bd8702-6186-4a59-ac88-c0e4ccfde41f - 6
73a1233c-b776-4f97-8032-527e7f8b73dd - 7
0ed17429-d0e7-4a54-9589-9a687fd630b5 - 8
60df67d8-a8c4-4ab7-bb32-e687f3e159f1 - 9
9316e80e-6d89-4fd4-a421-bee70abc13d0 - 10
b8490f31-6a43-4117-9cd3-a3263bf95b3b
What is a UUID generator?
A UUID generator creates Universally Unique Identifiers — 128-bit values that are statistically guaranteed not to collide with any other UUID generated anywhere else. Developers use them as primary keys for database rows, ids for API resources, names for test fixtures, message ids in queues, and identifiers in distributed systems.
UUIDs are useful because every machine can generate one independently and trust that nobody else will produce the same value. There is no central counter, no sequence to coordinate, no round-trip to a server. That makes them practical wherever a system needs to mint ids without asking permission.
*GUID* (Globally Unique Identifier) is Microsoft's name for the same 128-bit identifier. For everyday developer purposes, GUID and UUID mean the same thing — different ecosystems just prefer different names.
What you'll learn while generating UUIDs
- UUID v4 is the most common — purely random and great for general-purpose ids.
- UUID v7 is *time-ordered*, which gives you the same uniqueness as v4 but plays nicely with database indexes (rows insert in roughly chronological order).
- A UUID is an *identifier*, not a *secret*. Don't use it as an access token unless it is part of a larger security design.
How to generate UUIDs step by step
Pick a version
Choose v4 for random ids, v7 for time-ordered ids that index well, or v1 for legacy systems that need a timestamp + node id.
Set the count
Generate a single UUID for a quick id, or generate up to 1,000 at a time when seeding a database or mocking API responses.
Choose the format
Toggle uppercase, hyphens, and braces (
{...}) to match the convention your database, code, or platform expects.Click Copy or Copy All
Copy a single UUID or the whole list. Everything is generated locally in your browser.
UUID versions quick reference
The five widely-used UUID versions and when to reach for each one.
| Version | Source of uniqueness | When to use it |
|---|---|---|
| v1 | Timestamp + MAC address | Legacy systems; can leak the host's MAC |
| v3 | MD5 hash of a name + namespace | Deterministic ids derived from a string |
| v4 | Cryptographic randomness | Default for most apps — use this if unsure |
| v5 | SHA-1 hash of a name + namespace | Like v3 but with a stronger hash |
| v7 | Unix timestamp (ms) + randomness | Database primary keys — sortable by time |
UUID examples to try
Use a UUID inside a JSON record
Record
{ "id": "550e8400-e29b-41d4-a716-446655440000", "name": "Lesson 1", "createdAt": "2026-04-25T10:00:00Z"}APIs commonly expose UUIDs as strings in JSON. Many databases also support a native UUID column type that stores 16 bytes instead of 36 characters.
Compare formatting variants
Lowercase
550e8400-e29b-41d4-a716-446655440000
Uppercase
550E8400-E29B-41D4-A716-446655440000
Braced (Microsoft style)
{550E8400-E29B-41D4-A716-446655440000}
Hyphenless
550e8400e29b41d4a716446655440000
The same 128-bit value, four different surface formats. Pick one and stick with it inside a project — mixing formats causes confusing comparison bugs.
Common UUID mistakes
- Treating a UUID as proof that a user owns a resource. It is just an identifier — authorize requests separately.
- Using UUIDs as passwords or session tokens. They are not secret enough for that purpose by default.
- Mixing uppercase, lowercase, braced, and hyphenless formats inside the same database without a clear normalization step.
UUID Generator FAQ
How do I generate a UUID?
Open a UUID generator and click — that's it. In code, most platforms ship a built-in:
crypto.randomUUID() in browsers and Node.js, uuid.uuid4() in Python, UUID.randomUUID() in Java.What is a UUID used for?
UUIDs are used wherever a system needs a globally unique identifier without coordinating with a server. Database primary keys, REST resource ids, distributed event ids, log correlation ids, and anonymous user ids are all common uses.
Are UUID and GUID the same?
Which UUID version should I use?
Use UUID v4 for general-purpose random ids. Use UUID v7 if you want time-ordered ids that work well as database primary keys. Use v3 / v5 only when you specifically need deterministic ids from a name.
Can two UUIDs collide?
Theoretically yes, but for properly generated UUIDs the probability is negligible — generating a billion v4 UUIDs per second for 85 years would still leave the chance of any collision below one in a billion.
Should UUIDs be stored as strings?
Strings are fine and portable. Many databases also support a native UUID type that stores the value as 16 bytes — half the storage and faster comparisons. Use the format that fits your database and tooling.
