Comet is a web application model in which a long-held HTTPS request allows a web server to push data to a browser, without the browser explicitly requesting it.[1][2]Comet is an umbrella term, encompassing multiple techniques for achieving this interaction. All these methods rely on features included by default in browsers, such as JavaScript, rather than on non-default plugins. The Comet approach differs from the original model of the web, in which a browser requests a complete web page at a time.[3]
The use of Comet techniques in web development predates the use of the word Comet as a neologism for the collective techniques. Comet is known by several other names, including
Ajax Push,[4][5]Reverse Ajax,[6]Two-way-web,[7]HTTP Streaming,[7] and
HTTP server push[8]
among others.[9] The term Comet is not an acronym, but was coined by Alex Russell in his 2006 blog post.[10][citation needed]
In recent years, the standardisation and widespread support of WebSocket and Server-sent events has rendered the Comet model obsolete.