E4 is a British free-to-air television channel headquartered in London, United Kingdom owned by Channel Four Television Corporation. The "E" stands for entertainment, and the channel is mainly aimed at the 16–34 age group. Programming includes US imports such as Brooklyn Nine-Nine, The Goldbergs, The O.C., Smallville, Veronica Mars, Everwood, What About Brian, Desperate Housewives, How I Met Your Mother, 90210, Gotham, Rules of Engagement, The Big Bang Theory, RuPaul's Drag Race, 2 Broke Girls, Scream Queens, Revenge, and previously Friends (now on Comedy Central and Channel 5). Other programming includes homegrown British shows such as Skins, Misfits, The Inbetweeners, Shameless, Hollyoaks, Coach Trip, Celebs Go Dating, Made in Chelsea, and upcoming series Mae & George.

Its most successful broadcast to date was on 11 October 2010 when an episode of The Inbetweeners pulled in over 3.7 million viewers.^[1]

E4 launched as a pay-TV companion to Channel 4 on 18 January 2001. On 16 December 2004, Channel 4 announced that the subscription channel would become a free-to-air television channel by launching on the digital terrestrial television system. From its launch until the closure of ITV Digital, E4 was available as a bonus subscription channel.

E4 launched a Republic of Ireland service in June 2002 which has become the second most popular non-terrestrial channel in Ireland with 1.1% of the audience; Sky1 is the most popular.^[2]

Since 2006, E4 has sponsored the E4 UdderBELLY venue (part of Underbelly) at the Edinburgh Festival Fringe and Brighton Festival. The venue took the form of a giant upside cow in the purple colour of E4's logo.

In July 2007, it was announced Channel 4 would be launching E4 Radio, the first of a network of channels to be broadcast on DAB radio. The station was planned for launch in July 2008 and aimed at a similar demographic to its sister television channel,^[3] however this launch date was later delayed. In October 2008 Channel 4 announced it was abandoning its plans for digital radio, and thus scrapping the E4 Radio proposal.

On 14 December 2009, a high-definition simulcast of E4 launched on Sky+ HD channel 215, it was later added to Virgin Media on 1 April 2010.^[4][5] Unlike the other standard definition channels from Channel 4, which are free to air, E4 HD is only available with a subscription to either Sky's HD pack or Virgin Media's TV XL pack. Similar to this, the high-definition simulcast of its sister channel, Film4, is only available to Virgin Media's TV L and XL HD customers.^[6] E4 acquired the rights to several new US comedies throughout 2011 and 2012, a few of which were New Girl, Suburgatory, 2 Broke Girls, The New Normal, and The Mindy Project.

On 31 October 2013, E4 premiered a refreshed look as part of the channel's rebranding. This coincided with the debut of the seventh season of E4's most popular show, The Big Bang Theory, as well as the debut of new homegrown comedy Drifters.^[7]

On 27 September 2018, E4 was rebranded with a logo and identity harmonising itself within the Channel 4 family and with some new material to come as with those animated idents. This marked E4's first major rebrand since its launch in 2001.

On 14 January 2019, it was announced that Channel 4 had partnered up with the American programming block Adult Swim, to air Adult Swim shows for the first time ever on free-to-air UK television. This is part of a new brand partnership that will also see hundreds of hours of Adult Swim content being made available to stream for free on All 4. These shows include: Rick And Morty, Tim and Eric Awesome Show, Great job!, The Jellies!, Tim And Eric's Bedtime Stories, Robot Chicken, Dream Corp LLC and more.

The following is a list of the ten most watched shows on E4, based on Live +7 data supplied by BARB up to 11 November 2018.^[1] The number of viewers does not include repeats or airings on E4+1.

In August 2005, following the close of that year's Big Brother, E4 introduced the E4 Music programming block. The slot initially ran through much of the morning/daytime schedule, though was later reduced to mornings only, with the amount of scripted comedy and drama screened in daytime increased.

Prior to the launch of E4 Music, E4 was off-air during daytime for much of the year, only going on air in daytime for rolling coverage of reality shows such as Big Brother. The introduction of E4 Music led to E4 broadcasting 24/7 all year round. Initially, E4 Music would take a summer break to allow Big Brother coverage to replace it, but in later years Big Brother coverage was reduced, allowing a cut-down E4 Music to run during the summer.

In 2008, the launch of 4Music as a channel led to questions being asked about the future of E4 Music. However, E4 retained its commitment to music content, stating that E4 Music had been commissioned to run until at least the start of Big Brother in 2009.^[8]

At 10 am on Thursday 4 June 2009, the day before the launch of the 2009 Big Brother series, E4 Music ceased broadcasting.

Between 2001 and 2010 when the reality series Big Brother (and Celebrity Big Brother) were being transmitted on Channel 4, E4 devoted much of its schedule to live coverage from inside the Big Brother house; interactive features that gave access to additional camera angles have also been transmitted. The channel also had Big Brother voting options, Big Brother spin-off shows such as Big Brother Live, Big Brother's Little Brother, Big Brother's Big Mouth, Diary Room Uncut and Big Brother highlights repeats. Big Brother coverage was among the highest-rating programming on the channel, and came at a time when most of the year's US imports had ended. Past editions of the American and Continental African versions of Big Brother have also broadcast on E4.

Programme trailers sometimes have the narrator repeating things that characters have said, such as, in a trailer for Ugly Betty that includes one character asking Betty "Why are you crying in the bathroom?", the narrator immediately asks "Why is Betty crying in the bathroom?!". And on another occasion, he says "Oh No! Kerry Katona must be double booked." commenting on a cameo by Victoria Beckham. Sometimes the narrator appears to interact with the characters of the programme, especially notable in trailers for Miss Match and What About Brian. The announcers also occasionally gently poke fun at the series they introduce, such as heralding an episode of Life Unexpected by calling it "The show where no one - except Cate - has a sensible name."

Films are usually gently ridiculed in their promotion, such as with the voice of E4 telling viewers they "probably will" guess the ending of She's All That, naming actress Kim Cattrall as "That slaggy one from Sex and the City" when advertising Big Trouble in Little China, and re-dubbing a scene from Entrapment where the two characters are running along a rooftop before being caught in a helicopters' search light with "Catherine Zeta-Jones! This is the old man recovery unit!". There is also quite heavy use of British words which have generally fallen out of circulation, such as 'ruddy' and 'gaff'.

E4's continuity often sent up the channel's Friends-reliant schedule – while in the past, announcements would generally be the same for example "Now it's time to relax with Friends", more recently the announcers have been more inventive with phrases such as "....after an episode of Friends we've shown so many times the tape's gone a bit wobbly" before a Series 1 episode which indeed had a distorted soundtrack. There had only been a handful of days since the creation of E4 when Friends wasn't shown, but it was announced on 10 February 2010 that E4 and Channel 4 would stop airing the programme in Autumn 2011,^[9] although the series continues to be shown in Britain on Comedy Central.

On one occasion when a playout-error caused part of an episode of Desperate Housewives to be repeated, continuity announcer Dominic O'Shea said, "I know we repeat ourselves a lot on E4 but that was of course a technical fault. Hopefully we'll have it fixed by the time it's repeated on Sunday,"^[10] playing on the fact that many of E4's imported American drama programmes are shown at least twice for each episode.

Following the US premiere of Glee the first episode was aired as a sneak peek on 15 December 2009, one month before the actual premiere. Due to the launch of the second series of 90210 and the UK premiere of Glee both premiered with a "double bill" effect, the first two episodes of the second series of 90210 ("To New Beginnings" and "To Sext or Not to Sext") was screened on 5 January 2010, with the first two episodes of Glee ("Pilot" – which was already screened on 15 December 2009 as a sneak-peek and "Showmance") on 11 January 2010. The Cleveland Show and Accidentally on Purpose also premiered like this.