A webcast is a media file distributed over the Internet using streaming media technology. A webcast may either be distributed live or on demand. Essentially, webcasting is “broadcasting” over the Internet.

The generally accepted use of the term webcast is the "transmission of linear audio or video content over the Internet".

A webcast uses streaming media technology to take a single content source and distribute it to many simultaneous listeners/viewers.

The largest "webcasters" include existing radio and TV stations who "simulcast" their output, as well as a multitude of Internet only "stations". The term webcasting is usually reserved for referring to non-interactive linear streams or events.

Rights and licensing bodies offer specific "webcasting licenses" to those wishing to carry out Internet broadcasting using copyright material.

Webcasting is also used extensively in the commercial sector for investor relations presentations (such as Annual General Meetings), in E-learning (to transmit seminars), and for related communications activities. However, webcasting does not bear much, if any, relationship to the idea of web conferencing which is designed for many-to-many interaction.

The ability to webcast using cheap/accessible technology has allowed independent media to flourish. There are many notable independent shows that broadcast regularly online. Often produced by average citizens in their homes they cover many interests and topics. Webcasts relating to computers, technology, and news are particularly popular and many new shows are added regularly.

Origins

"Webcasting" was first publicly described and presented by Brian Raila of GTE Laboratories at InterTainment '89, 1989, held in New York City, USA. Raila recognized that a viewer/listener need not download the entirety of a program to view/listen to a portion thereof, so long as the receiving device ("client computer") could, over time, receive and present data more rapidly than the user could digest same. Raila used the term "buffered media" to describe this concept.

Raila was joined by James Paschetto of GTE Laboratories to further demonstrate the concept. Paschetto was singularly responsible for the first workable prototype of streaming media, which Raila presented and demonstrated at the Voice Mail Association of Europe 1995 Fall Meeting of October, 1995, in Montreux, Switzerland. Alan Saperstein (Visual Data, now known as Onstream Media (Nasdaq:ONSM), was the first company to feature video webcasting in June 1993 with HotelView, a travel library of 2 minute videos featuring thousands of hotel properties worldwide.

On November 7, 1994, WXYC, the college radio station of the University of North Carolina at Chapel Hill became the first radio station in the world to broadcast its signal over the internet.