Digital terrestrial television in the United Kingdom encompasses over 100 television, radio and interactive services broadcast via the UK's terrestrial television network and receivable with a standard television aerial. The majority of services, including those from the existing five analogue broadcasters, are broadcast free-to-air, and a further selection of encrypted Pay-TV services (such as ESPN) are also available.
Three companies provide DTT services in the UK: Freeview, Top Up TV, and (some) BT Vision. Freeview channels account for most, although not all, of the total available channels broadcast on digital terrestrial television, available at no extra cost and requiring no subscription other than payment of the annual TV licence fee. Top Up TV is a subscription service offering channels such as Sky Sports and ESPN, as well as on-demand content. BT Vision offers only Sky Sports and ESPN on DTT - their other services are carried via IPTV signals.
The digital broadcasting technology adopted in the UK is the DVB-T system (Digital Video Broadcasting – Terrestrial) carrying compressed digital audio, video and other data in a combined transport stream, using COFDM modulation. A total of six 'multiplexes' are broadcast in the UK, guaranteed to reach over 90% of the country when analogue signals are fully switched off. Three of the six multiplexes, carrying the free public service channels operated by the BBC, ITV, Channel 4, S4C and Channel 5, are guaranteed wider coverage still, reaching 98.5% of the country including areas dependent on low-power local relays.