# Private message

In computer networking, a private message, personal message, or direct message (abbreviated as PM or DM) refers to a private communication, often text-based, sent or received by a user of a private communication channel on any given platform. Unlike public posts, PMs are only viewable by the participants. Long a function present on IRCs and Internet forums, private channels for PMs have also been prevalent features on instant messaging (IM) and on social media networks. It may be either synchronous (e.g. on an IM) or asynchronous (e.g. on an Internet forum).

## Overview

There are two main types of private messages:
* One type includes those found on IRCs and Internet forums, as well as on social media services like Twitter, Facebook, and Instagram, where the focus is public posting, PMs allow users to communicate privately without leaving the platform.
* The second type are those relayed through instant messaging platforms such as WhatsApp and Snapchat, where users join the networks primarily to exchange PMs.
* A third type, peer-to-peer messaging, occurs when users create and own the infrastructure used to transmit and store the messages; while features vary depending on application, they give the user full control over the data they transmit. An example of software that enables this kind of messaging is Classified-ads.
Besides serving as a tool to connect privately with friends and family, PMs have gained momentum in the workplace. Working professionals use PMs to reach coworkers in other spaces and increase efficiency during meetings. Although useful, using PMs in the workplace may blur the boundary between work and private lives.
Some common forms of private messaging today include Facebook messaging (sometimes referred to as "inboxing"), Twitter direct messaging, and Instagram direct messaging. These forms of private messaging provide a private space on a usually public site. For instance, most activity on Twitter is public, but Twitter DMs provide a private space for communication between two users. This differs from mediums like email, texting, and Snapchat, where most or all activity is always private. Modern forms of private messaging may include multimedia messages, such as pictures or videos.

## History

The development of computers sparked the information revolution, which changed the way people communicate. Peter Drucker published an article centering on the theme that the computer is to the Information Revolution what the railroad was to the Industrial Revolution; railroads unified travel between the east and west coast of the United States, whereas computers unified communication across the entire globe. This revolutionized many different forms of communication, but particularly the personal message.
The first email system able to send mail between people using different host computers was launched via the ARPANET in 1971, and it revolutionized personal messaging by enabling users to send electronic messages to distant recipients. The popularity of email has since skyrocketed, and it continues to be a widely-used means of personal messaging. The advent of the Internet paved the way for communication through platforms and website portals like Yahoo!, and AOL. Instant messaging systems became popular in the late 1990s, and as Internet communication links improved and personal computers became more capable, this functionality was merged into systems that also included voice and video communication, such as Skype (launched in 2003). In 2008, Facebook Chat launched, which evolved into Facebook Messenger in 2011 and allows users to message each other via the Facebook site. Twitter followed suit and introduced direct messages to their site in 2013. Today, private messaging is a staple of established social media platforms and more recently-developed applications.

## Privacy concerns

In January 2014, Matthew Campbell and Michael Hurley filed a class-action lawsuit against Facebook for breaching the Electronic Communications Privacy Act. They alleged that private messages which contained URLs were being read and used to generate profit, through data mining and user profiling, and that it was misleading for Facebook to refer to the functionality as "private" with the implication that the communication was "free from surveillance".
In 2012, some Facebook users misinterpreted a redesign of the Facebook wall as publicly sharing private messages from 2008–2009. These were found to be public wall posts from those years, made at a time when it was not possible to like or comment on a wall post, making the notes look like private messages.