Text messaging, or texting, is the act of composing and sending electronic messages, typically consisting of alphabetic and numeric characters, between two or more users of mobile phones, fixed devices (e.g., desktop computers) or portable devices (e.g., tablet computers or smartphones). While text messages are usually sent over a phone network, due to the convergence between the telecommunication and broadcasting industries in the 2000s, text messages may also be sent via a cable network or Local Area Network.

The term originally referred to messages sent using the Short Message Service (SMS). It has grown beyond alphanumeric text to include multimedia messages (known as MMS) containing digital images, videos, and sound content, as well as ideograms known as emoji (happy faces and other icons).

As of 2017, text messages are used by youth and adults for personal, family and social purposes and in business, government and non-governmental organizations for communication between colleagues. As with emailing, in the 2010s, the sending of short informal messages has become an accepted part of many cultures. This makes texting a quick and easy way to communicate with friends and colleagues, including in contexts where a phone call would be impolite or inappropriate (e.g., calling very late at night or when one knows the other person is busy with family or work activities). Like e-mail and voice mail, and unlike landline or mobile phone calls (in which the caller hopes to speak directly with the recipient), texting does not require the caller and recipient to both be free at the same moment; this permits communication even between busy individuals. Text messages can also be used to interact with automated systems, for example, to order products or services from e-commerce websites, or to participate in online contests. Advertisers and service providers use direct text marketing to send messages to mobile phone users about promotions, payment due dates, and other notifications instead of using postal mail, email, or voicemail.

Text messaging is most often used between private mobile phone users, as a substitute for voice calls in situations where voice communication is impossible or undesirable (e.g., during a school class or a work meeting). Texting is also used to communicate very brief messages, such as informing someone that you will be late or reminding a friend or colleague about a meeting. As with e-mail, informality and brevity have become an accepted part of text messaging. Some text messages such as SMS can also be used for the remote controlling of home appliances. It is widely used in domotics systems. Some amateurs have also built own systems to control (some of) their appliances via SMS.

An alternative approach is to use end-to-end security software that runs on both the sending and receiving device, where the original text message is transmitted in encrypted form as a consumer SMS. By using key rotation, the encrypted text messages stored under data retention laws at the network operator cannot be decrypted even if one of the devices is compromised. A problem with this approach is that communicating devices needs to run compatible software. Failure rates without backward notification can be high between carriers.[citation needed]. International texting can be unreliable depending on the country of origin, destination and respective operators (US: "carriers"). Differences in the character sets used for coding can cause a text message sent from one country to another to become unreadable.