A tiny (<1KB), fast, and cryptographically secure UUID (v4) generator for Crystal.

This is the Crystal version of @lukeed/uuid


  1. Add the dependency to your shard.yml:

`yaml dependencies:

   github: krthr/uuix


  1. Run shards install


require "uuix"

puts UUIX.random # bc524cd7-5ec3-48c4-9bcc-e9013c69dd6e


Crystal 0.33.0 [612825a53] (2020-02-14)

LLVM: 8.0.0
Default target: x86_64-unknown-linux-gnu
        UUIX: 920.14k (  1.09µs) (± 9.68%)  880B/op        fastest
Crystal UUID: 647.32k (  1.54µs) (± 7.53%)  0.0B/op   1.42× slower


Taken from https://github.com/lukeed/uuid

The reason why this UUID.V4 implementation is so much faster is two-fold:

  1. It composes an output with hexadecimal pairs (from a cached dictionary) instead of single characters.
  2. It allocates a larger Buffer/ArrayBuffer up front (expensive) and slices off chunks as needed (cheap).

The internal ArrayBuffer is 4096 bytes, which supplies 256 random invocations.

A larger buffer would result in higher performance over time, but I found this to be a good balance of performance and memory space.


  1. Fork it (<https://github.com/krthr/uuix/fork>)
  2. Create your feature branch (git checkout -b my-new-feature)
  3. Commit your changes (git commit -am 'Add some feature')
  4. Push to the branch (git push origin my-new-feature)
  5. Create a new Pull Request