UUID vs GUID: Generate Version 4 IDs Online (When to Use Which)

UUID and GUID are the same idea with different accents. UUID is the RFC 4122 name. GUID is Microsoft's name for the same 128-bit value, usually printed with extra braces or uppercase hex. A version 4 UUID is 122 random bits plus a 4-bit version nibble. You use it when you need an ID that does not require a database round-trip to stay unique across machines.

UUID Generator creates v4 values in your browser with the same cryptographic randomness the platform gives to crypto.getRandomValues. Nothing is sent to a server. That matters if you are pasting IDs into configs that also contain secrets.

When v4 is the right choice

• Primary keys you mint in the client or in multiple services that cannot share a sequence.
• Idempotency keys for API writes.
• Filenames and object-store keys where two writers must not collide.
• Correlation IDs in logs.

v4 is random. It does not sort by time. If you need IDs that roughly increase as they are created (for B-tree locality), look at ULID or UUID v7, not this generator.

What people mix up

• UUID vs GUID: same identifier. Formatting differs: 3f63... vs {3F63...}. Parse both as 128-bit values.
• v1 vs v4: v1 embeds a timestamp and, historically, a MAC address. v4 is random. Prefer v4 unless you have a reason for time-based IDs.
• Collision: practically zero for v4 from a real CSPRNG. Do not use Math.random() to roll your own.
• Security: a v4 UUID is an identifier, not a session secret. Do not treat guessability the same as a 256-bit API key. For secrets, use a password / key generator.

How to generate one

1. Open UUID Generator.
2. Generate one or many v4 values.
3. Copy the format your stack wants: lowercase hyphenated is the usual JSON/API form.

Frequently asked questions

Is a GUID the same as a UUID?

Yes, for practical purposes. It is a 128-bit identifier. Names and string formats differ.

Can two UUID v4 values collide?

In real systems, you will hit operational bugs long before a CSPRNG v4 collision. Do not use a weak random source.

Should I use UUIDs as passwords?

No. Generate a dedicated secret. A UUID is unique, not high-entropy in the password-manager sense you want for credentials.

Open the UUID Generator and copy a v4 ID. Free, private, no signup.