Experiments in creating useful, locally-unique random IDs, in multiple languages.

A local ID is designed to have a compact string representation using 16 base-62 characters. Base 62 comprises only English alphabetic characters and numerals (i.e. [0-9A-Za-z]).

Example string values are: XDC9uT4O0PS5q1O5, me1KOWmWGjqv5XHa, W4n9Sj84Tv4f81HQ, quayf5S8Xua9Xnqw.

Each ID has 15 characters of random data and one check character, derived from the first 15.

This provides an approximately 90-bit random space. (For comparison, UUIDs are random in 128-bit space.)

• Compact string representation using only letters and numbers.
• Sufficient random space to be unique enough for most uses.
• Validity check to catch guessing attempts without needing to query existing values in a database (for example, if used to generate links like https://example.com/l/4jfPi9y19fyv1O0n).

• LocalId class in C#
• LocalId class in Kotlin
• LocalId module in JavaScript
  • HTML page with JavaScript that generates local ID values