A UUID (Universally Unique Identifier) is a 128-bit identifier formatted as 8-4-4-4-12 hexadecimal digits. Version 4 UUIDs are randomly generated and are the most common type.

How unique is a UUID v4?

Extremely unique. With 2^122 possible values, the probability of generating a duplicate is astronomically small, effectively zero for any real-world use case.

Is my UUID generated on a server?

All generation runs in your browser using the built-in crypto.randomUUID() API (v4) or a JavaScript implementation. No data is sent to our servers.

What is the difference between UUID versions?

v4 is randomly generated and the most common choice. v1 is time-based. v3 and v5 are name-based (deterministic). v7 combines a timestamp with randomness for sortable identifiers.

UUID generator

UUID generator is a data tool that produces RFC 4122 UUID v4 identifiers using the Web Crypto API. It generates single UUIDs, bulk batches up to thousands, and the nil UUID, with one-click copy or download. The tool runs in your browser.

Generated UUID

VERSION

Runs entirely in your browser

Dedicated pages

Direct links for each UUID type.

UUID v4 generator

Generate a random UUID v4 instantly using the browser's built-in crypto API. All processing runs in your browser, just click and copy.

Bulk UUID generator

Generate multiple UUID v4 values at once, up to 100 at a time. Copy all, or download as a text file.

Nil UUID

Generate or copy the nil UUID. All zeros (00000000-0000-0000-0000-000000000000). Used as a sentinel or default value in UUID-typed fields.

UUID v4 Generator

Generate a random UUID v4 instantly using your browser's secure random number generator. Free, private. Runs in your browser.

Bulk UUID Generator

Generate up to 100 random UUIDs at once in your browser. Copy all, or download as a plain text file. Free and private.

How to generate a UUID

Click "Generate" to create a new UUID v4 (or select another version from the dropdown).
The UUID appears in the output field instantly.
Click "Copy" to copy it to your clipboard.
Click Generate again for a fresh UUID, each one is unique.

Common uses

Generating unique identifiers for database records without a central coordinator
Creating unique IDs for user sessions, transactions, or events in an application, switch to a SHA-256 or MD5 fingerprint when you need a deterministic value from input data instead
Producing test data with guaranteed-unique keys. Pair with random strong passwords when you also need fake credentials in the same fixtures

Technical specification

Algorithm or formula: UUID v4 as defined in RFC 4122 (IETF, 2005). 122 random bits plus 6 bits encoding the version (4) and variant (10xx). Formatted as xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx hexadecimal digits.
Browser API or library: Web Crypto API (crypto.randomUUID() primarily; crypto.getRandomValues() as fallback). Backed by the operating system CSPRNG.
Input limits: Bulk mode generates up to 1,000 UUIDs per batch. No upper bound on lifetime generation count.
Output: Plain text UUID strings, one per line in bulk mode. Copyable to clipboard or downloadable as a .txt file.
Known limitations: v4 only; v1, v3, v5, and v7 are not currently generated by this tool. Collision probability is statistically negligible but non-zero.

Frequently asked questions

What is a UUID?: A UUID (Universally Unique Identifier) is a 128-bit identifier formatted as 8-4-4-4-12 hexadecimal digits. Version 4 UUIDs are randomly generated and are the most common type.
How unique is a UUID v4?: Extremely unique. With 2^122 possible values, the probability of generating a duplicate is astronomically small, effectively zero for any real-world use case.
Is my UUID generated on a server?: All generation runs in your browser using the built-in crypto.randomUUID() API (v4) or a JavaScript implementation. No data is sent to our servers.
What is the difference between UUID versions?: v4 is randomly generated and the most common choice. v1 is time-based. v3 and v5 are name-based (deterministic). v7 combines a timestamp with randomness for sortable identifiers.

Reviewed and tested May 26, 2026.