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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.
crypto.randomUUID() API. Each UUID is a 128-bit value formatted as 32 hex digits in 8-4-4-4-12 groups, with version bits set to 4 and variant bits set to RFC 4122.On this page
- How to Use
- What Is a UUID?
- UUID Versions
- UUID vs Auto-Increment IDs
- Common Use Cases
- Privacy
- Recommended Reading
- More Free Developer Tools
- Frequently Asked Questions
- What is a UUID v4 and when should I use one?
- Are UUID v4s truly unique?
- Is crypto.randomUUID() secure enough for production use?
- What is the difference between the output formats?
- References
How to Use#
- Set the count (1–100 UUIDs at a time)
- Choose a format (lowercase, UPPERCASE, {braces}, or no-dashes)
- Click Generate
- Click Copy All to grab every UUID at once
What Is a UUID?#
crypto.getRandomValues() API — the same cryptographically secure random number generator used in production systems. No data leaves your device.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
More Free Developer Tools#
- Free JSON Formatter & Validator Online
- Free Base64 Encoder & Decoder Online
- Free Hash Generator
- Free URL Encoder & Decoder Online
- Free Word Counter & Text Analyzer Online
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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