GNSSpy is a free and open source library for handling multi-GNSS and different versions (2.x and 3.x) of RINEX files. It performs basic Precise Point Positioning (PPP) algorithms to calculate coordinates of the GNSS stations precisely. Therefore, the Multi-GNSS Experiment (MGEX) products are used within the package. It also calculates the ionospheric delay by using International GNSS Service (IGS) atmospheric models for single frequency receivers and minimize its effect by combining frequencies for the receivers have at least dual frequency. GNSSpy can be used for editing (slicing, decimating, merging) and quality checking for RINEX files. It can be successfully used for visualizing GNSS data such as skyplot, azimuth-elevation, time-elevation, ground track and visibility plot. Additionally, this library can be used for basic geodetic computations such as geodetic positions on reference ellipsoid and projection computations. GNSSpy can be downloaded from the GitHub repositories (https://github.com/GNSSpy-Project/gnsspy). The toolkit is still being improved by the authors.