UUID Generator v4 — RFC 4122, Cryptographically Strong

UUID Generator v4 — RFC 4122, Cryptographically Strong

Generate version 4 UUIDs (Universally Unique Identifiers) using your browser’s cryptographic random source. v4 UUIDs are random 128-bit values formatted as xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx, where the “4” indicates version and “y” is one of 8/9/A/B. The collision probability is so vanishingly small that you can generate billions of UUIDs without any practical risk of duplication. Useful for database primary keys, distributed system identifiers, file names, session IDs, and anywhere you need a globally unique value without coordination.

Features

• RFC 4122 compliant v4 UUIDs with proper version/variant bits
• Cryptographically secure via crypto.randomUUID (modern browsers) or crypto.getRandomValues fallback
• Bulk generation: 1 to 500 UUIDs at once
• 8 output formats:
  • lowercase (default) — 3f29b1d2-8c5e-4a7f-9b3e-1d4c8f2e7a6b
  • UPPERCASE — 3F29B1D2-8C5E-4A7F-9B3E-1D4C8F2E7A6B
  • no hyphens — 3f29b1d28c5e4a7f9b3e1d4c8f2e7a6b
  • {braces} — Microsoft GUID style
  • (parens) — alternative wrap
  • "quoted" — ready for code/JSON
• 5 separators: newline, comma+newline, inline comma, space, semicolon
• Download as .txt

Common uses

• Database primary keys: better than auto-increment for distributed systems
• Session/request IDs: trace logs across services
• File naming: avoid collisions when uploading user files
• API correlation IDs: connect frontend requests to backend logs
• Test data: populate dev databases with realistic IDs
• License keys / activation codes

How unique is a v4 UUID?

A v4 UUID has 122 random bits (the other 6 bits encode version/variant). That gives you ~5.3 × 10³⁶ possible values. To have a 50% chance of generating a collision, you’d need to produce about 2.7 × 10¹⁸ UUIDs — that’s 2.7 quintillion. For practical purposes, UUIDs are unique. Just don’t reuse them across runs of your application without storing them.

Privacy

All generation happens in your browser. No UUIDs are uploaded or logged.