uuid.lol

Articles

6 articles on picking an ID format, reading one apart bit by bit, and what each one costs you. Every example runs in your browser.

Pillars

  • How to Choose an ID Format

    Pick by what the ID has to do: UUID v7 for database keys, Nano ID for URLs people read, UUID v5 when the same input must give the same ID.

    Updated

  • Every UUID Version, and Which One You Want

    RFC 9562 defines eight versions. Four matter in new code: v4 for random, v5 for reproducible, v7 for sortable, v8 for custom layouts.

    Updated

  • Using IDs as Database Keys

    What a random 128-bit primary key costs in insert throughput, index size and cache locality, and how much of it a time-ordered ID gives back.

    Updated

  • What Your IDs Give Away

    A UUID v4 is 122 bits from a CSPRNG and is not guessable. Every other format here publishes a timestamp, a MAC address, or a row count.

    Updated

  • Length, Alphabets, and How Much Entropy You Need

    Entropy is bits, not characters. A 21-character Nano ID carries 126 bits against a UUID v4's 122, in 15 fewer characters.

    Updated

Explainers