Over the top (OTT) is a media distribution practice that allows a streaming content provider to sell audio, video, and other media services directly to the consumer over the internet via streaming media as a standalone product, bypassing telecommunications, cable or broadcast television service providers that traditionally act as a controller or distributor of such content.
In 2011, the Canadian Radio-Television and Telecommunications Commission (CRTC) stated that it "considers that Internet access to programming independent of a facility or network dedicated to its delivery (via, for example, cable or satellite) is the defining feature of what have been termed 'over-the-top' services".
In contrast to video on demand video-delivery systems offered by cable and IPTV, which are tightly managed networks where channels can be changed instantly, some OTT services such as iTunes require that the video be downloaded first and then played, while other OTT players such as Apple TV, Amazon Unbox or Netflix offer movie downloads that start playing before the download completes (streaming).
An OVD was defined by the FCC as:
any entity that provides video programming by means of the Internet or other Internet Protocol (IP)-based transmission path where the transmission path is provided by a person other than the OVD. An OVD does not include an MVPD inside its MVPD footprint or an MVPD to the extent it is offering online video programming as a component of an MVPD subscription to customers whose homes are inside its MVPD footprint.
In broadcasting, over-the-top content (OTT) is the audio, video, and other media content delivered over the Internet without the involvement of a multiple-system operator (MSO) in the control or distribution of the content. The Internet provider may be aware of the contents of the Internet Protocol (IP) packets but is not responsible for, nor able to control, the viewing abilities, copyrights, and/or other redistribution of the content. This model contrasts with the purchasing or rental of video or audio content from an Internet service provider (ISP), such as pay television, video on demand, and from internet protocol television (IPTV). OTT refers to content from a third party that is delivered to an end-user, with the ISP simply transporting IP packets.
This section needs expansion with: a thorough, sourced description of the types of OTT content current transmitted. You can help by adding to it. (December 2016)
OTT television, usually called internet television or streaming television, remains the most popular OTT content. This signal is received over the internet or through a cell phone network, as opposed to receiving the television signal from a terrestrial broadcast or satellite. Access is controlled by the video distributor, through either an app or a separate OTT dongle or box, connected to a phone, PC or television set. By mid-2017, 58 per cent of US households would access one in a given month and advertising revenues from OTT channels exceeded those from web browser plug-ins.
OTT messaging is defined as instant messaging services or online chat provided by third parties, as an alternative to text messaging services provided by a mobile network operator. An example is the Facebook-owned mobile application WhatsApp, that serves to replace text messaging on Internet connected smartphones. Other providers of OTT messaging include Viber, WeChat, Skype, and Google Allo. 
OTT voice calling, usually called VOIP, capabilities, for instance, as provided by Skype, WeChat, Viber, and WhatsApp use open internet communication protocols to replace and sometimes enhance existing operator controlled services offered by mobile phone operators.
Consumers can access OTT content through Internet-connected devices such as phones (including Android, iOS, and Windows-type mobile devices), smart TVs (such as Google TV and LG Electronic's Channel Plus),[better source needed] set-top boxes (such as Apple TV, Fire TV and Roku), gaming consoles (such as the PlayStation 4, Wii U, and Xbox One), and desktop and laptop computers and tablets.