In this study, requirements of landslide susceptibility mapping by a Mamdani fuzzy inference system (FIS) are identified, and a single standalone application (GeoFIS) is developed. GeoFIS includes two main open source libraries, one for GIS operations and the other for creating Mamdani FIS. As a result, it is possible to construct a landslide susceptibility map based on expert opinion, to visualize maps instantly and to measure model performance. GeoFIS supports all steps of the landslide susceptibility mapping process, starting from data deployment and ending with performance measurement. In GeoFIS, visual controls allow use of the inferred results and actual landslide occurrence information, and ROC-AUC values are calculated automatically. Moreover, a confusion matrix is produced, and alternative measurement schemes such as recall are suggested, to reveal those performance details not observable with ROC-AUC and to create trust in the inferred results. GeoFIS is applied to the Trabzon region of northern Turkey, and the recall and ROC-AUC values were .902 and .602, respectively. (C)2014 Elsevier Ltd. All rights reserved.