The diploma thesis deals with the problem of online data scatterness and how to combine and display data in one place. When addressing this issue the car ads were selected as the topic, which we can search through on different sites in Slovenia. I wanted to aggregate the data and present these data in a attractive and transparent way and to improve user experience in this thesis. For developing the diploma I selected the waterfall development model. I followed the phases in the cycle. First I performed the analysis and then planned how to set up the system. I decided to split the system into two parts, on the back end and front end of the application. The back end is supposed to serve the data through the REST application programming interface while the front end is supposed only to display data. I obtained the data from other websites with the Scrapy library, which filled the back end system with data and kept it fresh. The front end is implemented as a one-page application and uses JWT for authentication. The result of the thesis is a system that collects, processes and stores data and a web site with a material design layout which displays ads and allows users to enter ads.