Cross-Platform Development
Cross-platform development means writing an app once and then running it on multiple systems, for example on iPhones and Android phones. This saves time and money, but often costs some speed and closeness to the respective device.
A phone from Apple and a phone with Google's Android system are very different on the inside. They understand different programming languages and offer developers different tools. In the past, a company therefore had to write its app completely from scratch twice, once for each system. Cross-platform development is the counter-approach to this: you write the program code only once and then let it run on both systems. An intermediary tool translates or mediates between the shared program code and the respective device. The same principle also applies to programs that are supposed to work simultaneously under Windows, macOS, and Linux.
Why companies don’t want to build the same app three times
The main reason is simply money. Two separate apps mean two teams, two bug lists, and two schedules. With shared program code, both versions often share 70 to 90 percent of the code. A new feature then only needs to be built once and tested once.
There is also an advantage that users notice directly. With separate apps, one version almost always lags behind. The Android variant gets a feature months later than the iPhone variant, or vice versa. Shared code automatically keeps both versions at the same level.
The price for this is control. Anyone who programs for a single system alone can exploit every peculiarity of the device, for example a new camera feature on release day. Cross-platform tools often only support such innovations with a delay. For games with high graphics demands or apps that continuously read sensors, the detour is sometimes noticeably slower.
The shared code and the translation layer
Technically, there are two major families of solutions. One family generates genuine apps for the respective system from the shared code. Well-known representatives are Flutter from Google and React Native from Meta. They come with their own building blocks for buttons, lists, and menus that look the same on both systems or can be adapted.
The second family essentially wraps a website in an app shell. The content is built using the languages of the internet and displayed in an invisible browser window. This is particularly cheap because many developers already master these languages anyway. In return, such apps sometimes feel a bit sluggish, because there is an additional layer between operation and device.
A helpful image is an interpreter. The shared code speaks one language, the device another, and the tool translates between them. Translating always costs a bit of time and rarely happens entirely without losses. That’s why many teams still write small parts of their app separately for each system, for example access to special hardware.
Which well-known apps are built this way
Many programs used daily are built cross-platform. The desktop versions of Spotify, Discord, and Visual Studio Code all run on web technology inside an app shell. On mobile phones, among others, parts of Instagram and the app of Deutsche Bahn use such approaches. Ideally, users notice nothing of this.
The term appears in business news when companies talk about development costs. A start-up with five programmers usually cannot afford two separate apps. Large corporations with hundreds of developers, on the other hand, more often opt for separate versions because they want maximum quality. Some companies also switch back and publicly justify this with speed problems.
A common misconception is that cross-platform means exactly the same operation everywhere. Good apps still adapt: a back button sits differently on Android than on the iPhone. What is shared is primarily the logic behind it, i.e., calculations, data management, and server access. The interface often remains deliberately different.