Which UUID version?

Universally Unique IDentifiers versions are defined by the RFC4122.

They are 5 different versions that have different implementations to generate Unique Identifiers.

v1 Time Uses the CPU clock cycle to calculate a unique ID

v2 MAC Uses the CPU clock cycle and MAC address to generate a unique ID.

v3 MD5 Uses a namespace value to salt the MD5 Hash (128 bits).

v4 Random Uses Pseudo-random numbers to generate a unique ID.

v5 SHA-1 Uses a namespace value to salt the SHA-1 Hash (160 bits).

API

Generally, a UUID library will expose all 5 versions and a few helper functions.

• Version: Provides UUID RFC version
• Parse: Convert UUID string to array of bytes
• Stringify: Convert array of bytes to UUID string
• Validate: Check if UUID is valid
• Nil: All bits are set to 0
  • 00000000-0000-0000-0000-000000000000

Ranking

Uniqueness v1 👊 v2 👊 v4 v4 Random v1 and v2 are similar, but the cpu cycle is predictable.	Hashing v3 👊 v5 v5 SHA-1 v5 SHA-1 has a stronger encryption than v3 MD5.
Protected v2 👊 v1 👊 v4 👊 v3 👊 v5 v5 SHA-1 v1 and v2 are similar, but the MAC address can make your system less secure.	Overall v1 👊 v2 👊 v3 👊 v5 👊 v4 v4 Random v4 is generally the best option in most use cases.