This thesis delves into development of web application, focusing on geothermal boreholes in Stockholm. Geothermal energy is becoming increasingly popular in Sweden as a viable option for heat pumps. With rising energy demand, more GSHPs are expected to be installed. Currently, Stockholm County has 131,192 active boreholes, leading to high density in certain areas. A new tool is needed to assess ground temperature before further installations to avoid overcrowding and overexploitation. This thesis describes a tool developed for temperature simulation in Stockholm County, providing a comprehensive view of the current situation. The tool integrates mathematical temperature calculations with actual borehole data plotted on the map. The tools is developed by utilizing the full aspects of the web development such as using javascript for frontend and python for the backend main calculation part. The tool is developed to simulate the temperature response at the new locations and existing boreholes till present and for forecasted years. The thesis includes simulations of boreholes in dense areas to demonstrate how ground temperatures are affected even in locations without boreholes, due to the influence of neighboring ones. The results cover both the initial years and projections for the next 20 years. Additionally, a heatmap is produced to show ground temperature trends, helping identify areas with lower temperatures and guiding future energy decisions based on current conditions.