Cross-platform applications are a relatively new alternative to developing applications available on multiple platforms compared to developing so-called native applications only available for one platform. This study aims to research the performance of applications developed in cross-platform frameworks to native applications. This was researched with the help of an experiment. The experiment was designed to test different well-known algorithms with a high time complexity in an attempt to simulate more demanding applications. The native applications were written with Java for Android and Swift for iOS. The cross-platform apps were tested on both iOS and Android and were written with the React Native and Flutter frameworks. The Flutter and React Native frameworks were also chosen due to belonging to different categories of frameworks. The results show that the native applications performed better on both iOS and Android compared to both of the cross-platform applications, but there was a difference between the loss of performance between the two cross-platform frameworks. The react native application with the tests used showed a higher loss of performance compared to the flutter application on both iOS and Android. Moreover the react native application was slower on the iOS devices when compared to the Android devices.