UUID Generator
Generate RFC 4122 version 4 UUIDs with this browser’s CSPRNG. Copy one or a list, strip hyphens, or inspect a pasted identifier.
Tool input stays in your browserDid you know · Encoding
Base64 padding uses = to round the output to a multiple of four characters.
Click Generate to create UUID v4 values in this browser.
Inspect
What a v4 UUID actually is
A UUID is 128 bits, usually written as 32 hex digits in the 8-4-4-4-12 form. Version 4 fills almost all of those bits from a cryptographically strong generator. Two nibbles are reserved: the version field is 4, and the variant bits are 10 so the identifier is an RFC 4122 UUID rather than an older NCS or Microsoft GUID layout. Collision risk is negligible for ordinary application IDs.
This page does not generate v1 (time + MAC), v5 (name SHA-1), or v7 (time-ordered) values. Those are different layouts and would be misleading if they showed up next to a “random UUID” button.
Hyphens, case, and bulk generate
Databases and APIs disagree on presentation. Postgres uuid columns typically store the hyphenated form; some HTTP APIs want 32 compact hex digits; a few specs insist on uppercase. The checkboxes only change how the same 16 bytes are printed. Generate up to 500 at a time when you need seed data, and copy the whole list as one newline-separated block.
Inspecting a pasted UUID
The inspect field accepts hyphenated or compact hex. It reports the version nibble and the RFC 4122 variant. A value that looks like a UUID but uses a different variant (Microsoft GUID layout, for example) is still decoded so you can see why a library rejected it.
Why it is private
Bytes come from crypto.getRandomValues in this tab. Open DevTools, switch to the Network tab, and generate a batch: no request carries those IDs. That matters when the IDs will become primary keys or session identifiers.
UUID generator FAQ
Generate UUID v4, GUID vs UUID, uniqueness, hyphens, and how to inspect a UUID in the browser.
What is a UUID generator?
A UUID generator creates 128-bit identifiers, usually written as 8-4-4-4-12 hex. This UUID generator produces RFC 4122 version 4 (random) UUIDs using the Web Crypto CSPRNG. You can copy one or many, drop hyphens, or switch to uppercase.
How do I generate a UUID v4 online?
Set the count (1–500), choose hyphens and case, and click Generate. Each value is a random UUID / GUID suitable for primary keys and request ids. Generation happens in this browser; ids are not fetched from a server.
What is the difference between UUID and GUID?
GUID is Microsoft’s name for the same 128-bit identifier family. RFC 4122 UUID v4 is the random layout this tool emits (version nibble 4, variant bits 10). Inspect a pasted value to see version and variant if a library rejected it.
Are generated UUIDs unique?
Version 4 UUIDs have enough random bits that collisions are negligible for ordinary apps. They are not time-ordered (that would be v7) and not derived from a name (v5). Do not treat a UUID as a secret by itself.
Can I inspect an existing UUID?
Yes. Paste a hyphenated or compact 32-hex UUID into Inspect to see canonical form, version, and RFC 4122 variant. That is the UUID inspector on this page.