To cite package ‘base64url’ in publications use:

Lang M (2020). base64url: Fast and URL-Safe Base64 Encoder and Decoder. R package version 1.4, https://github.com/mllg/base64url.

Corresponding BibTeX entry:

  @Manual{,
    title = {base64url: Fast and URL-Safe Base64 Encoder and Decoder},
    author = {Michel Lang},
    year = {2020},
    note = {R package version 1.4},
    url = {https://github.com/mllg/base64url},
  }