UUID Generator

What is a UUID?

A UUID (Universally Unique Identifier), also called a GUID, is a 128-bit label used to uniquely identify information in computer systems. UUIDs are written as 32 hex digits in 5 groups: xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx. They are used as database primary keys, session IDs, file names, and API identifiers.

What is UUID v4 and how is it different from v1?

UUID v4 is generated using cryptographically secure random numbers — making it unpredictable and safe for public-facing systems. UUID v1 is generated using the current timestamp and the machine's MAC address — making it traceable and unsuitable for privacy-sensitive use. UUID v4 is the most commonly used version today.

Are UUIDs truly unique?

UUID v4 has 122 bits of randomness, giving 2¹²² (~5.3 × 10³⁶) possible values. The probability of generating two identical UUIDs is astronomically small — roughly 1 in a billion if you generate a billion UUIDs per second for 85 years. For all practical purposes, UUIDs from different systems will never collide.

Is it safe to use UUIDs as database primary keys?

Yes. Benefits: global uniqueness across distributed systems, no central sequence generator needed, no information leakage about record counts. Downsides: 16 bytes vs 4 bytes for integer keys, random insertion order can reduce B-tree index performance. PostgreSQL's gen_random_uuid() and MySQL's UUID() natively support UUID primary keys.

What is the difference between UUID with and without hyphens?

Standard UUID includes hyphens: 550e8400-e29b-41d4-a716-446655440000. No-hyphen removes dashes: 550e8400e29b41d4a716446655440000. Both represent the identical 128-bit value. Some systems (older databases, certain APIs) expect the no-hyphen form. The format is purely cosmetic.

How are the UUIDs generated here?

This tool uses the browser's built-in crypto.randomUUID() function, which generates cryptographically secure random UUIDs using the operating system's CSPRNG (Cryptographically Secure Pseudo-Random Number Generator) — the same source used for cryptographic operations. The UUIDs are unpredictable and safe for use as tokens and identifiers.