LASE ( ) is XAS analysis software that pays special attention to the handling of statistical and systematic errors. Once estimated, statistical errors are propagated across all analysis steps and can be used in the fitting process, both as an (optional) weighting scheme and to obtain the distribution of the fit parameters. The influence of systematic errors is investigated through experiment simulation, adding one or several sources of such errors. LASE also provides a graphical interface to build and visualize the structural model used in FEFF6 simulations and in the fitting process, and tools to deal with XAS cartography experiments.