Most people think the default messages app is the only app you can use to chat with your friends even without the internet. Here, I discuss other apps available for that purpose.
Chomp SMS
This app is available only for Android phones right now. It gives you a lot of freedom to customize the app according to your theme. You can even send Multimedia Messages and block some numbers. It is available in two versions that are paid and free. You get some additional benefits by choosing the paid one.
Signal Offline Messenger
This app relies on peer to peer network and has a reach of 100 meters. The registration and verification of this app are offline, and no information passes through the cloud. Thus, the info is not at risk of getting hacked. Related Article: A guide to exporting chats on Whatsapp
Hike
You can easily contact people around you without the internet using this app. You can also transfer media using this and there is no limit for that. This app also supports has hundreds of stickers with which you can express yourself better. Hike is available for Android and IOS.
Handcent Next SMS
This android app is also another app with which you can send and receive texts without any internet connection. It works just like the native phone messages app.
FireChat
This app allows you to create chat rooms and discuss things without the internet. FireChat connects devices up to 200 feet away from each other without any issues.
The Serval Mesh
This app allows you to easily make phone calls, send text messages and even or files even when no internet or cellular network is working. It uses a store and forward system identified as Rhizome and is open-source.
Voter
This app directly connects with people using a peer to peer network, Bluetooth or any similar technology. With connected devices nearby and you can not only send text messages but also send images. It does not require any type of network, it creates one for its own using mesh network. Whilst many of these apps are limited by distance, they can be handy for communication in class, at camps, or any other places where many people are gathered.