What is the difference between UUID v1, v4, and v7?

UUID v1 is based on the current timestamp and a node identifier (here replaced with pseudo-random bytes for privacy). UUID v4 is entirely random. UUID v7 encodes a 48-bit Unix millisecond timestamp in the most-significant bits, making it monotonically sortable — useful as a database primary key. NIL is the special all-zeros UUID used as a null placeholder.

Are UUIDs generated here cryptographically secure?

UUID v4 and v7 use crypto.getRandomValues, which is a cryptographically strong random number generator provided by your browser. UUID v1 uses a pseudo-random clock sequence. NIL UUIDs are deterministic (all zeros) by definition.

What UUID format should I use for a database primary key?

UUID v4 is the most common choice for random primary keys. UUID v7 is increasingly preferred when index performance matters because its timestamp prefix keeps inserts near the end of a B-tree index, reducing page splits. If your database stores UUIDs as binary(16), consider the no-hyphens format for easier conversion.

Is any data sent to a server when I generate UUIDs?

No. All UUID generation runs entirely in your browser via the Web Crypto API (crypto.getRandomValues). No UUID, no quantity, and no format choice is transmitted to any server.

UUID Generator

Name: UUID Generator
Availability: InStock
Author: Nham Vu

Select a UUID version, choose a quantity, pick a format, then click Generate. Copy all results or download as a .txt file.

UUID Settings

UUID Version

Quantity (1–1000)

Output Format

Results

Summary

Select a UUID version, choose a quantity, pick a format, then click Generate. Copy all results or download as a .txt file.

How it works

Select the UUID version you need: v1, v4, v7, or NIL.
Enter the number of UUIDs to generate (1 to 1000).
Choose an output format such as lowercase, uppercase, no hyphens, braced, or URN.
Click the Generate button to produce the UUIDs instantly in your browser.
Use Copy All to copy every UUID to your clipboard, or click Download to save them as a .txt file.

Use cases

Generate primary keys for database records that require globally unique identifiers.
Create v7 time-ordered UUIDs for systems that benefit from sortable IDs.
Produce bulk UUIDs for seeding test datasets or staging environments.
Generate a NIL UUID (all zeros) as a placeholder or sentinel value in data schemas.

Frequently Asked Questions

Last updated: 2026-06-09 · Reviewed by Nham Vu