What Is a UUID (and a GUID)?
A universally unique identifier (UUID) is a 128-bit value used to label data without a central authority handing out numbers. A GUID (globally unique identifier) is Microsoft's name for the same idea — the terms are interchangeable, and this uuid generator produces values valid for either. The format is standardized by RFC 4122, which defines several distinct ways to build one.
Properly generated, an identifier from this uuid creator is unique enough that a collision is not a realistic concern — how unique depends on which version you pick, covered below.
Which UUID Version Should You Use?
This free uuid generator supports the four versions developers reach for most. Match your requirement to a version rather than defaulting blindly:
| Version | Built From | Pick This When You Need… |
|---|---|---|
| UUID v1 | Timestamp + node ID | Chronological event or audit-log ordering |
| UUID v4 | Random numbers | Maximum unpredictability — API keys, session IDs, general-purpose IDs |
| UUID v5 | Namespace + name (SHA-1 hash) | The same input to always reproduce the same identifier |
| UUID v7 | Unix timestamp + random | Sortable, index-friendly database primary keys |
Not sure? Version 4 is the safest general-purpose default among every random uuid generator option — it's unpredictable, private, and supported everywhere.
UUID vs GUID: Is There Really a Difference?
Not in practice. GUID is Microsoft's historical branding for the identifier format that RFC 4122 calls a UUID — both describe the same 128-bit value, and any tool that accepts one accepts the other. You'll see "GUID" most often in .NET, SQL Server, and Windows APIs, and "UUID" everywhere else, including Linux, Java, and web standards.
The one place the distinction ever matters is formatting convention: Windows tooling sometimes wraps a GUID in curly braces (e.g. {f47ac10b-58cc-4372-a567-0e02b2c3d479}), which this online uuid generator supports via its brace-formatting option.
Where UUIDs and GUIDs Get Used
- Database keys across distributed systems — no central counter needed to avoid collisions between machines
- API keys and session identifiers — unguessable, unlike sequential numbers
- Correlation and trace IDs — following one request across microservices in logs
- File names and object storage keys — naming conflicts become a non-issue
- Deterministic content addressing — version 5 turns a URL or name into a stable, reproducible ID
Storing UUIDs in a Database
Every major database engine supports UUID storage, either as a native type or a standard function — see our dedicated guides for PostgreSQL, MySQL, SQL Server, MongoDB, SQLite, and Oracle. The version you choose has real storage and index consequences: purely random identifiers can fragment a B-tree index on write-heavy tables, which is exactly the problem UUID v7 was designed to solve.
Generate a Unique Identifier in Any Programming Language
Prefer code over a browser tool? Every mainstream language ships a built-in or well-supported way to generate one — see our guides for Python, JavaScript, Java, C#, Go, and Rust, among others.
Frequently Asked Questions
How can I create a UUID online?
Click the Generate UUID button above — this uuid generator tool creates a new identifier entirely in your browser using the Web Crypto API, with nothing sent to a server. Pick your version and format, then copy it in one click.
Which UUID version should I use?
Version 4 for most cases — it's random, private, and the most widely supported. Reach for v1 or v7 when you need chronological sorting, and v5 when the same input must always produce the same identifier.
Where can I get a GUID online?
Right here — a GUID and a UUID share the same 128-bit format, so any identifier this tool generates is a valid GUID for .NET, SQL Server, or any Microsoft-ecosystem application.
Are UUIDs randomly generated?
Only version 4 is fully random. Version 1 derives from a timestamp and node identifier, version 5 is deterministic (hashed from a namespace and name), and version 7 combines a Unix timestamp with random bits. Choose based on whether you need randomness, reproducibility, or sortability.