The development of apps in a cross-platform framework is something that has been appearing more over the latest years. But the knowledge of knowing which of the two popular frameworks, React Native, and Flutter are most efficient when it comes to resource management and general comparisons are less known. This is what this thesis investigates.

To find out the comparisons between React Native and Flutter we created two similar apps and document the process of creating an app with the selected frameworks. To get data on the differences when developing an app with these frameworks, we made a survey to get more experienced developers' input. We then did performance tests of the apps to be able to compare the results of the respective framework. The applications we built had several similar functionalities that we used to measure the performance. We also touched on the subject of comparison between a cross-platform framework and a native framework. To do this we performed a literature review on related work to conclude the approaches.

From our result, we could conclude that the performance of the Flutter app had a slight advantage over the React Native app. But the difference was not that remarkable, and the overall development was fairly similar. There were some differences to the approaches of development when it came to less experienced developers compared to more experienced developers which we learn from our survey. More experienced developers tended to use external debugging tools, while less experienced used built-in tools such as console commands.

Finally, we want to conclude that both Flutter and React Native has their pros and cons. Both frameworks have a big community which is growing everyday, but we believe that Flutter might overtake the popularity from React Native due to its slight performance superiority.From our literature review we can conclude that both approaches has their advantages and it depends a lot on the concept of the app. When developing a more complex app, the native approach is superior. When developing smaller apps with shorter life periods, cross-platform will faster get the app on the market.