Generate cryptographically-random version-4 UUIDs one at a time or in bulk — created locally, never on a server.
Quick presets
UUID Generator
Inspect a UUID
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Runs in your browser — nothing you enter is uploaded or stored.
ToolFeather · RFC 4122 v4
Scratchpad auto-saved
Stored in this browser (localStorage)
About the UUID Generator
A UUID (Universally Unique Identifier), also called a GUID, is a 128-bit value written as 32 hexadecimal digits in the pattern 8-4-4-4-12. Version 4 UUIDs are generated from random data, which makes the chance of two ever colliding vanishingly small — so they're the standard way to label database rows, files, events, and API requests without a central counter.
This generator uses the browser's cryptographically-secure crypto.getRandomValues, sets the version and variant bits exactly as RFC 4122 requires, and can produce up to 500 at once. Toggle uppercase or strip the hyphens to match whatever format your system expects.
Everything happens on your device — no request is made to any server, so the identifiers you generate are yours alone and are never logged.
Examples
Need a primary key? Generate one v4 UUID like 3f2a…-…-4b1c.
Seeding test data → generate 100 at once and paste them into your fixtures.
A system that dislikes hyphens → tick Remove hyphens for a 32-char string.
UUID versions & format
Version
Based on
Typical use
v1
Timestamp + MAC address
Time-ordered IDs (leaks host info)
v3 / v5
Hash of a name
Deterministic IDs from a namespace
v4
Random data
General-purpose unique IDs (most common)
v7
Timestamp + random
Sortable, database-friendly (newer)
The format is always xxxxxxxx-xxxx-Mxxx-Nxxx-xxxxxxxxxxxx, where M marks the version (4 here) and N the variant. This generator produces version 4 — the right default for most needs — and can output them uppercase or with the hyphens removed to match your system.
Frequently asked questions
9 answers
Are these UUIDs truly unique?
They're version-4 UUIDs built from 122 random bits, so the probability of a collision is astronomically small — small enough to treat them as unique in practice.
Is the randomness secure?
Yes. It uses the browser's crypto.getRandomValues, a cryptographically-secure random source, not Math.random.
What's the difference between UUID and GUID?
None in practice — GUID is Microsoft's name for the same 128-bit identifier. This tool's output works as either.
Do the UUIDs ever leave my browser?
No. They're generated locally with JavaScript and never sent anywhere.
What is a UUID / GUID?
A UUID (Universally Unique Identifier), also called a GUID, is a 128-bit value written as 32 hexadecimal digits in the pattern 8-4-4-4-12 (e.g. 3f2504e0-4f89-41d3-9a0c-0305e82c3301). It's used to label things — database rows, files, requests — without a central counter.
What is a version-4 UUID?
Version 4 UUIDs are generated almost entirely from random data. This tool uses the browser's cryptographically-secure random source and sets the version and variant bits exactly as RFC 4122 requires, so the output is standards-compliant.
Are these UUIDs unique enough to rely on?
Yes. A v4 UUID has 122 random bits, so the chance of generating the same one twice is astronomically small — small enough to treat them as unique in any practical application.
What's the difference between UUID and GUID?
None in practice. GUID is Microsoft's name for the same 128-bit identifier; the value this tool produces works wherever either term is used.
Are the UUIDs generated on a server?
No — they're generated entirely in your browser and never transmitted, so they're private to you.