To cite effectsize in publications use:

Ben-Shachar M, Makowski D, Lüdecke D (2020). “Compute and interpret indices of effect size.” CRAN. R package, https://github.com/easystats/effectsize.

Corresponding BibTeX entry:

  @Article{,
    title = {Compute and interpret indices of effect size},
    author = {Mattan S. Ben-Shachar and Dominique Makowski and Daniel
      Lüdecke},
    journal = {CRAN},
    year = {2020},
    note = {R package},
    url = {https://github.com/easystats/effectsize},
  }