Free UUID Generator Online — Generate v4 UUIDs Instantly

Instantly generate random UUID v4 identifiers with this free online tool. Create up to 100 UUIDs at once in lowercase, uppercase, braces, or no-dash format. Perfect for database keys, test data, and API development. No signup required.

TL;DR: Generate RFC 4122–compliant version 4 UUIDs instantly in your browser. Create up to 100 at once in lowercase, uppercase, braces, or no-dash format — no signup, no server calls, fully client-side.

How to Use

1. Set the count (1–100 UUIDs at a time)
2. Choose a format (lowercase, UPPERCASE, {braces}, or no-dashes)
3. Click Generate
4. Click Copy All to grab every UUID at once

What Is a UUID?

A UUID (Universally Unique Identifier) is a 128-bit identifier standardized by RFC 4122. The version 4 (v4) variant generated by this tool uses random or pseudo-random numbers, making collisions astronomically unlikely — you’d need to generate about 2.71×10¹⁸ UUIDs to have a 50% chance of a single collision.

UUID Versions

• v1 — Based on timestamp + MAC address. Sortable but leaks hardware info.
• v4 — Fully random. Most popular for general-purpose use. This tool generates v4.
• v5 — Deterministic hash (SHA-1) of a namespace + name. Same input always gives the same UUID.
• v7 (new) — Timestamp-ordered random UUID. Sortable like v1 but without MAC address. Great for database primary keys.

UUID vs Auto-Increment IDs

• UUIDs — Globally unique, no coordination needed, safe to expose publicly, but larger (36 chars) and non-sequential
• Auto-increment — Sequential, compact, great for indexing, but require a central authority and leak record count

Common Use Cases

• Database primary keys — generate IDs client-side without round-trips
• API request tracing — correlate logs across microservices
• File naming — avoid collisions in uploads and temporary files
• Session tokens — unique session identifiers (combine with proper entropy)
• Test data — populate mock databases with realistic unique IDs

Privacy

UUIDs are generated entirely in your browser using JavaScript’s Math.random(). No data is sent anywhere. For cryptographic use, prefer crypto.getRandomValues() in production code.

Recommended Reading

Go deeper into distributed systems and unique identifier design:

• Designing Data-Intensive Applications — essential reading for distributed systems and unique IDs
• System Design Interview — essential reading for ID generation at scale
• Database Internals — essential reading for primary keys and indexing

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Frequently Asked Questions

What is a UUID v4 and when should I use one?

A UUID v4 (Universally Unique Identifier, version 4) is a 128-bit random identifier defined by RFC 4122. Use them as primary keys in databases, unique request IDs in APIs, or correlation IDs in distributed systems whenever you need a globally unique value without a central authority.

Are UUID v4s truly unique?

Practically yes. A v4 UUID has 122 random bits, yielding 5.3 × 10³⁶ possible values. You would need to generate about 2.71 × 10¹⁸ UUIDs to have a 50% chance of a single collision — far beyond any real-world usage.

Is crypto.randomUUID() secure enough for production use?

Yes. crypto.randomUUID() uses a cryptographically secure pseudorandom number generator (CSPRNG) provided by the operating system. It is suitable for security-sensitive identifiers, tokens, and keys.

What is the difference between the output formats?

Lowercase (default) produces standard 550e8400-e29b-41d4-a716-446655440000. Uppercase is the same in capitals. Braces wraps it in curly braces {...} as used by Microsoft APIs. No-dashes removes hyphens for compact storage.

References

• RFC 4122 — A Universally Unique IDentifier (UUID) URN Namespace — The IETF standard defining UUID formats and generation algorithms
• MDN — Crypto.randomUUID() — Browser API documentation for generating RFC 4122 v4 UUIDs
• MDN — Crypto.getRandomValues() — The underlying CSPRNG API used as a fallback for UUID generation