Digital broadcasting proposals in the 1990s always envisioned a high-definition service for each network, and to that end, Nine Network was allocated its own entire DVB-T multiplex. However, late amendments to the Broadcasting Services Act 1992 added a mandate for simulcasting in standard definition, while still promoting high definition through the use of a quota in 2003, requiring a minimum number of hours of native HDTV content.
From the launch of digital TV on 01/01/01, the Nine Network's high definition service, a simulcast of its standard definition and analogue services, was heavily simulcasting Nine's standard definition content upconverted to HD. From 2002, this was interspersed with a loop of high definition demonstration material during business hours, for viewing in the showrooms of television retailers, at the conclusion of an equivalent service by Network Ten.
2002 saw the first revenue-generating broadcast in native HD in Australia, with the drama Judging Amy. Nine increased its native HD output in the lead-up to the commencement of the HD quota on July 1, 2003, from which point it broadcast a minimum of 1,040 hours of native HD content per year. The largest portion of this was The Today Show.
9HD was officially announced as a part-time (or "breakaway") multichannel on 27 September 2007, to replace the Nine Network's existing high definition simulcast service through the use of an amendment to the Broadcasting Services Act 1992 in 2006. The Broadcasting Legislation Amendment (Digital television) Act 2006 permitted television networks to launch digital multichannels, provided that they are broadcast exclusively in high definition.
Although originally expected to be the first free-to-air commercial television channel introduced to metropolitan areas since 1988, the surprise launch of rival Seven HD, on 15 October 2007, one month before transmissions were scheduled to begin meant that 9HD was not the first high definition multichannel in Australia. Following this, plans for a November launch in 2007 were postponed until 2008. On 10 March 2008, PBL Media announced that it would launch the channel on 17 March 2008 at 10:30pm, with its first program, Nightline.
The re-branded 9HD officially commenced transmission on 17 March 2008 from PBL Media's four metropolitan owned-and-operated stations, TCN Sydney, GTV Melbourne, QTQ Brisbane and NTD Darwin, in addition to WIN Corporation's two metropolitan stations NWS Adelaide, and STW Perth as well as on its regional stations RTQ Queensland, WIN southern New South Wales, VTV Victoria, and TVT Tasmania. The first official program on launch night began at 10:30pm, Nine News's late-night news program Nightline. This was followed by military drama E-Ring at 11:00pm, with the movie Unanswered Questions marking the end of the first night of exclusive transmission for 9HD after its conclusion at 2am.
All 9HD breakaway programming ceased transmission on Sunday 2 August 2009 in preparation for the launch of GO! (now 9Go!) on 9 August. As a result, 9HD became a full simulcast of Nine's main channel.
9HD was replaced by the GEM (now 9Gem) multichannel on 26 September 2010, which unlike the previous incarnation, was a full-time breakaway and branded separately (with one exception being the London Olympics). This removed the HD simulcast of Channel Nine entirely to allow a third channel to fit on Nine's DVB-T multiplex (due to technical and regulatory limitations). As a result, Nine lost all youth, news and comedy content in HD, but instead screened female, crime and lifestyle content on its only HD facility.
For the purposes of some sport such as cricket, GEM was still used on an occasional basis to broadcast HD under the Wide World of Sports brand, though not necessarily as a simulcast with Nine. As such, this was generally limited to events outside of prime time, while those with more prominence continued to be shown on the Nine Network.
On 26 November 2015, Nine recommenced simulcasting in HD on channel 90. As a result, 9Gem was moved to channel 92 and reduced to standard definition.
This revival marked 9HD's switch to H.264/MPEG-4 AVC broadcasting, allowing the broadcaster to operate at full quality in 1920x1080i50 resolution using a lower bitrate than in 2007. This gives the network the ability to provide all the other multichannel services launched since 2009, such as 9Go!, at the same time.
Other than during the 2008-2010 period of 9HD as a breakaway service, the channel has been a broadcast of simulcast content from Nine's main channel 'Nine' in high definition. However, in the 2008-2010 period, exclusive breakaway programming was broadcast for several hours a day, usually from 10.30pm til around 2am the next morning most nights of the week. During other hours, 9HD remained a simulcast of Nine.
In May 2009, in addition to late night breakaways, 9HD marked changes to its daytime schedule with the addition of breakaway programs between 11am and 4.30pm. The new-look daytime schedule featured a midday movie and repeats of Bewitched and I Dream of Jeannie.
Exclusive programming which aired during breakaways on the channel included Comedy Inc. (reruns only), E-Ring, The Mountain, Related, Invasion, Four Kings, The Comeback, Big Day, Twenty Good Years, Hot Properties, Happy Hour, Kidnapped, Notes from the Underbelly and a few episodes of Justice. 9HD also broadcast most of Nine Melbourne's football-themed programming, notably Footy Classified and the AFL version of The Footy Show to a national audience.
In its former inception, 9HD was available in 1080i50 high definition through Nine's owned-and-operated stations, TCN Sydney, GTV Melbourne, QTQ Brisbane, NWS Adelaide, STW Perth, NTD Darwin and NBN Northern New South Wales. 9HD programming was also carried via WIN Corporation's regional stations RTQ Queensland, WIN Southern New South Wales, VTV Victoria and TVT Tasmania as "WIN HD". 9HD was not carried by regional affiliates Southern Cross in Spencer Gulf & Broken Hill or Imparja Television.
Upon its revival on 26 November 2015, 9HD returned to 1080i50 high definition, but was broadcast in MPEG-4 format as opposed to the standard MPEG-2 format. 9HD covered all Nine-owned metropolitan stations as well as its Darwin station. Nine's regional station NBN Northern New South Wales launched 9HD on 1 March 2016.
Regional affiliate WIN Television announced on 10 February 2016 it would launch its own HD simulcast in the coming months. It was later confirmed the HD simulcast would be titled WIN HD and would launch on 1 March 2016. Four WIN regions were excluded from the 1 March launch date. Griffith, Tasmania, and Eastern South Australia did not receive the channel until 2 March 2016 due to technical issues. In addition, the Regional WA station did not launch the channel until 10 March 2016.
Upon the media shakeup on 1 July 2016, WIN lost its Nine affiliation in favour of Southern Cross Austereo. As such, WIN HD switched its feed to the Ten HD feed in all WIN markets. Southern Cross then took over the Nine affiliation in Queensland, Southern NSW, Victoria, Spencer Gulf, SA and Broken Hill, NSW. In these areas except Spencer Gulf, SA and Broken Hill, NSW, 9HD became available from 1 July 2016, over a month earlier from the original mid-August expectation that cited the time consumption of installing new broadcasting equipment. 9HD also became available in Tasmania on 1 July 2016 when the joint venture station TDT changed its affiliation from Ten to Nine.
As of 10 March 2016, no plans were announced yet in launching the channel in BDN Broken Hill NSW, MDN Griffith NSW, MDV Mildura, GDS Spencer Gulf SA, SDS/RDS Eastern SA, WDT Regional WA and Remote Central & Eastern Australia.
Originally the logo was only displayed in place of the standard Nine Network logo when native HD programming replaced upscaled material, and switched from "HDTV" to "HIGH DEFINITION" in 2003. When the network dropped the dots from their logo, a more custom design was deployed. When 9HD's breakaway service was launched in 2008, the logo became a permanent fixture even on upscaled material, and used the Nine Network's nine dot logo with "HD" in a circle beside the numeral 9. The on-air look featured a dark look inside one of the 3D discs used in the 2008 logo. The slogan accompanying 9HD promotions was "You're Watching 9HD", which was replaced by " Choose Nine and Welcome Home", the same slogan as the primary channel, after breakaway programming ceased on 2 August 2009. An updated logo introduced when broadcast recommenced on 26 November 2015, accompanied by the slogan "Crystal Clear".