, I would assume that you are trying to make an instant messaging app yourself. I haven’t really made any mainstream app yet, but I have worked on creating such apps or businesses. I mean exclusive messaging apps. The concept is pretty much the same, the only difference I guess would be the number of users using your app. Like any app, you can start from scratch, which I guess is the first thing people think about. Coding, programming, and all that. You could do that, but it will be time-consuming, like a lot. Money too, considering that you would need to hire a team of developers to do it. Unless you do it all yourself of course, but that too will take a lot of time. The best route to go in my opinion would be to get a WhatsApp clone app and modify it. These clone apps have many of the features built-in, even if you need new features they can be added easily. It would be better to choose an app development company for this, an experienced one too at that. All you would have to do is tell them what you need and they will customize the clone app with your branding and the features you need. And also make sure that they help you out with getting it up on the app stores. Most of these apps are available for both iOS and Android OS so there shouldn’t be a problem there. Best of luck to you buddy. Hope this help.