A browser extension is a plug-in that extends the functionality of a web browser.

Some extensions are authored using web technologies such as HTML, JavaScript, and CSS.

Others are developed using machine code and application programming interfaces (APIs) provided by web browsers, such as NPAPI and PPAPI.

Browser extensions can change the user interface of the web browser without directly affecting viewable content of a web page; for example, by adding a browser toolbar.

YouTube is an American video-sharing website headquartered in San Bruno, California.

The service was created by three former PayPal employees—Chad Hurley, Steve Chen, and Jawed Karim—in February 2005.

Google bought the site in November 2006 for US$1.65 billion; YouTube now operates as one of Google's subsidiaries.

The site allows users to upload, view, rate, share, add to favorites, report and comment on videos, subscribe to other users, and it makes use of WebM, H.264/MPEG-4 AVC, and Adobe Flash Video technology to display a wide variety of user-generated and corporate media videos.

Available content includes video clips, TV show clips, music videos, short and documentary films, audio recordings, movie trailers and other content such as video blogging, short original videos, and educational videos.

Home cinema, also called home theater or home theatre, refers to home entertainment audio-visual systems that seek to reproduce a movie theater experience and mood using consumer electronics-grade video and audio equipment that is set up in a room or backyard of a private home.

In the 1980s, home cinemas typically consisted of a movie pre-recorded on a LaserDisc or VHS tape; a LaserDisc or VHS player; and a heavy, bulky large-screen cathode ray tube TV set.

In the 2000s, technological innovations in sound systems, video player equipment and TV screens and video projectors have changed the equipment used in home theatre set-ups and enabled home users to experience a higher-resolution screen image, improved sound quality and components that offer users more options (e.g., many of the more expensive Blu-ray players in 2016 can also "stream" movies and TV shows over the Internet using subscription services such as Netflix).

The development of Internet-based subscription services means that 2016-era home theatre users do not have to commute to a video rental store as was common in the 1980s and 1990s (nevertheless, some movie enthusiasts buy DVD or Blu-ray discs of their favourite content).