Open source geospatial software provides code that is freely available to the public. It has several advantages, including keeping code in the public domain, high software quality through peer review, improved security, and interoperability. There are many open source projects for desktop GIS, web mapping servers, web mapping clients, spatial databases, and full open source geospatial web platforms. However, open source geospatial software still faces challenges of lack of commercial support, skilled personnel, and visibility compared to proprietary alternatives.