Cross-platform software is software that can run on multiple platforms (Windows, Linux, and macOS). It can be divided into two categories: software that is created or compiled for each platform separately and software that can run directly on multiple platforms without additional steps. Using Flutter, a cross-platform mobile application has been created with which users can share photos of their favorite locations. The application contains a registration form, interactive maps, automatic detection of GPS location, marking of favorite locations within the application (so-called liking). Flutter is a set of user interface design tools that allows you to create mobile, web and desktop applications from the same code. Flutter is developed by Google. Flutter is free and open source so anyone can contribute to its development. The main advantage is that it reduces development time and reduces the complexity of the process of writing applications for multiple platforms (writing the same application for mobile devices and for the web). Application designers can use it for prototyping. Version 1.0 was released on December 4, 2018. Some parts of Flutter, such as full support for desktop applications, have not yet arrived in the latest stable version. But thousands of Flutter applications have already been released and installed on hundreds of millions of devices. Google, eBay, BMW, Groupon, Nubank and Tencent are just some of companies that use it. When writing Flutter applications, the Dart programming language is used. Flutter runs on Windows, macOS, and Linux within a Dart virtual machine. Dart, developed by Google, has a syntax similar to the C programming language and is specifically optimized for writing multi-platform applications.