Zellio.io

Online UUID Generator

Create cryptographically-random v4 UUIDs and tokens on demand.

Processed locally — nothing is uploaded

About UUID & Token Generator

Produces a single value or a whole batch, drawn from your browser's cryptographic generator rather than a seeded pseudo-random one. The distinction matters as soon as the value becomes a database key or a session token.

Generate RFC-4122 version-4 UUIDs one at a time or in bulk for database keys, request IDs and idempotency keys. Each is produced by your browser's cryptographic random source and never leaves your device.

Generate RFC-4122 version-4 UUIDs and secure random tokens one at a time or in bulk. UUIDs are 128-bit identifiers with such a vast range that collisions are practically impossible, making them ideal for database keys, request IDs and idempotency keys.

Copy a single identifier or generate hundreds at once. Version 4 is random rather than sequential, which is what makes it safe to expose in a URL but slower as a database primary key than a monotonic id.

Learn how this works

Generating What You Need: QR Codes, Passwords, IDs & FilesA practical guide to generating QR codes, strong passwords, UUIDs, barcodes and PDFs — all free and fully in your browser.8 min read

Frequently asked questions

What kind of UUID does this generate?

Version 4 — the random variant defined by RFC 4122. 122 of its 128 bits come from your browser's cryptographic random source, with the remaining bits fixed to mark the version and variant.

Could two generated UUIDs ever collide?

In practice, no. The space is so large that you would need to generate billions per second for decades before a collision became likely. That is precisely why v4 UUIDs are safe to mint independently on many machines with no coordination.

Should I use a UUID as a database primary key?

It depends on the workload. UUIDs let you generate IDs without a round trip and avoid leaking row counts, but random values scatter writes across a B-tree index, which hurts insert performance at scale. UUIDv7 or a sequential ID is often better there.

Common Use Cases

  • •Creating unique identifiers for test fixtures or seed data
  • •Generating a correlation ID for tracing a request across services
  • •Producing a unique key without a round trip to the database

More UUID & Token Generator tools

UUID & Token Generator

Related tools

QR Code GeneratorGenerate scannable QR codes for links, WiFi, contacts, SMS and email.Password GeneratorCreate strong, random passwords with a live strength meter.Focus TimerA crisp Pomodoro timer with work, short and long break cycles.Lorem Ipsum GeneratorGenerate placeholder paragraphs, sentences or words instantly.