Question 1

What is a UUID?

Accepted Answer

UUID (Universally Unique Identifier) is a 128-bit identifier formatted as 32 hexadecimal digits in five groups: xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx. It is designed to be globally unique without requiring a central registry or coordination.

Question 2

What is the difference between UUID v1 and UUID v4?

Accepted Answer

UUID v1 uses the current timestamp and the device's MAC address — making it time-ordered but traceable. UUID v4 uses purely random numbers — making it untraceable and the recommended choice for most applications where privacy or security matters.

Question 3

Can two UUIDs ever be the same?

Accepted Answer

Theoretically possible, practically impossible. UUID v4 has 2^122 possible values (~5.3 × 10^36). If you generated one billion UUIDs per second, it would take hundreds of billions of years to statistically likely produce a collision.

UUID ジェネレーター (v1–v8)

UUID Version

オプション

結果

よくある質問