Messages are mainly used for informal and personal communication, and are often the subject of correspondence of confidential information about users that should not be available to third parties. There are applications that enable encrypted  communication through chat services. 

SMS communication is similar to chat communication, the only difference is that the internet is used as a data transmission medium in chat communication, while the standard network of mobile phones (GSM, 2G, 3G, 4G, etc.) is used for SMS messages. It is important to emphasize that both parties must use encryption in order for the system to be secure. A free and open source online chat app that provides end-to-end encryption  by default is Signal. It is available for iOS and Android, as well as a desktop app. It provides a wide range of security options, such as self-destructing messages, PIN protection or encrypted video calls. You can also use Telegram where Secret Chats need to be enabled for end-to-end encryption.

Phone/Tablet Apps Encryption Computer/Laptop