This compressed file is supplementary to the article 'Anion-dependent strength scale of interactions in ionic liquids from X-ray photoelectron spectroscopy, ab initio molecular dynamics, and density functional theory'. Its contents are two-fold: (1) Experimental X-ray photoelectron spectroscopy data of a select few ionic liquids studied in the article, in .vms format which can be accessed using CasaXPS and (2) The input and (some) output files of all the ionic liquids studied computationally. These computational files will allow you to replicate both the ab initio molecular dynamics (MD) (calculated using CP2K) and the density functional theory (DFT) (calculated using VASP) calculations shown in the article.