Skip to content
Lizely

UUID Generator

Generate cryptographically random RFC 4122 v4 UUIDs in bulk — copy one or all, in your browser.

Privacy: your files never leave your device. All processing happens locally in your browser.

How to use

  1. 1.Enter how many UUIDs you want (1 to 100).
  2. 2.Optionally toggle uppercase or remove hyphens to match your format.
  3. 3.Click Generate, then copy any single UUID or use Copy all.

About UUID Generator

A UUID (Universally Unique IDentifier) is a 128-bit label used to identify records without a central authority handing out numbers. It is written as 32 hexadecimal digits in a canonical 8-4-4-4-12 pattern, such as f47ac10b-58cc-4372-a567-0e02b2c3d479. This generator produces version 4 UUIDs, the random variant defined by RFC 4122 and its 2024 replacement RFC 9562.

A UUID carries a version and a variant. Of the 128 bits, 6 are fixed: 4 encode the version (the 13th hex digit is always 4) and 2 encode the variant (the 17th hex digit is always 8, 9, a, or b), leaving 122 bits of pure randomness. Version 4 is the random one; other versions derive their bits from timestamps (v1, v7), names via hashing (v3, v5), or a mix — but v4 needs no clock, MAC address, or namespace, which makes it the simplest to generate safely anywhere.

Those 122 bits come from your platform's cryptographically secure random number generator — the Web Crypto API's getRandomValues — not the weak, predictable Math.random used by many quick scripts. That distinction matters: a CSPRNG makes each UUID unguessable and statistically independent, which is exactly what you want for identifiers that may surface in URLs, logs, or client-side code.

With 122 random bits, collision odds are astronomically small. You would need to generate on the order of a billion UUIDs per second for roughly 85 years before the chance of a single duplicate reaches even 50% — the birthday-bound math is why teams treat v4 UUIDs as effectively unique without coordinating across machines.

That coordination-free property is the whole point. Version 4 UUIDs can be minted independently on any device, so they suit database primary keys, distributed and offline-first systems, idempotency keys, correlation and trace IDs, file and object names, and API request identifiers — anywhere two systems must create IDs at once without colliding. If you specifically need time-ordered keys for index locality, UUIDv7 is the newer choice; for unordered uniqueness, v4 remains the default.

Uppercasing the digits or stripping the hyphens changes only the text form, never the underlying 128-bit value or its uniqueness, so pick whichever matches your database column or code style. This tool generates every UUID locally in your browser tab: choose how many you need, adjust the format, then copy them one at a time or all at once. No value is ever transmitted to a server, so it is safe for production secrets and internal identifiers alike.

Methodology & sources

UUID v4 per RFC 4122 / RFC 9562: 122 random bits from the platform CSPRNG (crypto), with version and variant bits set per spec.

Frequently asked questions

What is a version 4 UUID?
A version 4 UUID is a 128-bit identifier defined by RFC 4122 (updated by RFC 9562) whose 122 usable bits are random. Six bits are reserved: four fix the version to 4 and two set the variant, so the 13th hex digit is always 4 and the 17th is 8, 9, a, or b.
Are these UUIDs safe to use as unique IDs?
Yes. With 122 random bits from a cryptographically secure generator, the probability of ever producing a duplicate is negligible for real-world volumes, which is why v4 UUIDs are widely used as database keys and distributed IDs without central coordination.
Is my data sent to a server?
No. Every UUID is generated locally in your browser using the Web Crypto API. Nothing you generate or copy is transmitted anywhere, so the tool is safe for production identifiers and secrets.

Related tools

Developer Tools guides

View all