UUID v4 Generator Online

What Is This Tool?

A UUID (Universally Unique Identifier) is a 128-bit identifier written as 36 characters, like 550e8400-e29b-41d4-a716-446655440000. Version 4 UUIDs are generated from random data, which makes collisions so unlikely they can be ignored in practice: you could generate a billion UUIDs per second for decades before a duplicate becomes probable.

UUIDs are used as database primary keys, request IDs for tracing, filenames, API keys, and anywhere you need an identifier without coordinating with a central authority.

UUIDs are standardized in RFC 4122, revised in 2024 as RFC 9562 — the revision kept v4 unchanged and added UUIDv7, a timestamp-ordered variant designed to index better as a database key.

Why Use It?

• Cryptographically secure: uses crypto.randomUUID(), not weak Math.random().
• Bulk generation — up to 500 UUIDs at once, one per line, ready to paste.
• Uppercase and no-hyphen options for systems with specific format requirements.
• Runs offline in your browser; the UUIDs are never sent anywhere.
• Free and instant, no login.

How to Use

1. Choose how many UUIDs you need (1–500).
2. Optionally check "Uppercase" or "Remove hyphens".
3. Click "Generate UUIDs".
4. Click "Copy All" to copy the whole list.

Example

Input

Count: 3

Output

f47ac10b-58cc-4372-a567-0e02b2c3d479
9c858901-8a57-4791-81fe-4c455b099bc9
16fd2706-8baf-433b-82eb-8c7fada847da

Each UUID is generated independently from secure random data.

Common use cases

• Database primary keys: UUIDs let you generate a valid ID before an insert, useful for offline-first apps or when the client needs to reference a record before the server confirms it.
• Distributed systems: multiple servers can generate IDs independently with no coordination and no risk of collision — unlike auto-increment integers, which need a single source of truth.
• Idempotency keys: sending the same UUID with a retried API request lets the server recognize and safely ignore a duplicate submission.
• Test fixtures and seed data: bulk-generate hundreds of unique IDs at once for populating a test database or mock API responses.
• React/Vue list keys: when list items don't have a natural unique ID yet, a generated UUID works as a stable key during development.

Limitations to know about

UUIDs aren't sortable by creation time — v4's randomness means new IDs don't sort near each other in a database index, which can hurt insert performance at scale (this is why UUID v7, timestamp-ordered, exists as an alternative). If you need time-ordering plus uniqueness, v7 or a Snowflake-style ID is a better fit than v4.

A UUID alone isn't a security credential. It's unguessable in the sense that you can't predict one from another, but it was never designed with the auditability, expiry, or revocation features a real auth token needs — use a dedicated session/API token library for that.

How the randomness actually works

A v4 UUID has 122 bits that are genuinely random (the other 6 bits are fixed to mark the version and variant, per the RFC 4122 spec). This tool gets that randomness from crypto.getRandomValues() via the browser's Web Crypto API — the same underlying source used for TLS keys and other cryptographic operations, not the much weaker Math.random(), which is predictable enough that some older UUID libraries built on it have been criticized for generating guessable IDs.

To put the collision odds in concrete terms: with 122 random bits, you'd need to generate about 2.71 quintillion UUIDs before there's a 50% chance of even one collision — several orders of magnitude more than any single application will ever create. This is why UUID v4 is treated as effectively collision-free in practice, even though it's not mathematically impossible.

Frequently Asked Questions