Ceefax (, punning on "seeing facts") was the world's first teletext information service and a forerunner to the current BBC Red Button service. Ceefax was started by the BBC in 1974 and ended, after 38 years of broadcasting, at 23:32:19 BST (11:32 PM BST) on 23 October 2012, in line with the digital switchover being completed in Northern Ireland.

To receive a desired page of text on a teletext-capable receiver, the user would enter a three-digit page number on the device. Once the page number was entered, the selected page would display on the user's screen upon its actual transmission, which would have required a wait of several seconds. There were many pages to choose from and they could be displayed either on a black background or superimposed over the broadcast programme picture. This latter feature made it technically possible for the first time for British broadcasters to transmit subtitles which could be turned on or off by the viewer, rather than as part of the broadcast image.