The UK digital terrestrial television platform commercially launched a high definition service in spring 2010, initially seeing relatively modest sales of receiver equipment, taking just under a year to pass 1m.
However, as Freeview HD has expanded to cover 80% of the population, sales of integrated TVs and set top boxes have picked up, passing 3.1m units as of the end of September.
Of the 10.2 million homes with Freeview on their main television set, around 1.75m have the Freeview HD service, roughly one in five Freeview homes.
Freeview, which is owned by its five shareholders (the BBC, Sky, Channel 4, ITV and transmission firm Arqiva), has sold more than 70m products since it launched in 2002.
Freeview managing director Ilse Howling said that 90% of Freeview HD sales have been for integrated TVs (TVs with Freeview HD built-in), while 10% have been for set top boxes.
She said that this is indicative of Freeview's overall shift from mainly an STB service in the early years to a more integrated offering built into TVs today.
Howling noted that further improvements to flash memory drives and solid state storage in TV technology could result in sets built with both HD and the Freeview+ timeshift services in the future.
Many Freeview HD-equipped TV sets also come with Smart functionality, meaning they have a web connection supporting services such as BBC iPlayer, YouTube, Facebook and LoveFilm.
Howling believes that by the end of 2012 there will be 8m Freeview HD homes in the UK with access to Smart TV functionality, particularly as the digital switchover will be completed.
Currently 80% of the UK can receive HD through Freeview, but that will increase to almost very household by October when analogue TV is switched off in all parts of the UK. That will also coincide with Freeview's tenth birthday as a TV platform.
In a statement, Howling added: "Breaking through the three million sales barrier is huge achievement for Freeview HD. Television remains an incredibly important part of people's lives and Freeview has continued to provide the most-loved programmes in the format people want since Freeview launched in 2002. Our focus now is to ensure we continue to develop and give viewers what they want over the next ten years, post-switchover and beyond.
"We're seeing a shift in what viewers want from their TV provider. The ability to access high definition has become something people expect as normal when buying a new television. Also, most Freeview HDTVs and some Freeview+ HD recorders now offer smart features giving viewers access to more entertainment such as BBC iPlayer, YouTube and Facebook."
Freeview HD currently offers four HD channels - BBC One HD, the BBC HD Channel (due to turn into the BBC Two HD under BBC plans), ITV1 HD and Channel 4 HD - but a fifth channel is scheduled to launch in April 2012.
Ofcom's deadline for parties to submit proposals for the available fifth HD channel slot on Freeview expired last week, and currently Channel 5 is viewed as the frontrunning bidder.
Channel 5 was expected to bring Channel 5 HD to Freeview last year, but failed to meet Ofcom's requirements for launch, resulting in the capacity being handed back to the BBC and enabling the launch of BBC One HD.
Howling said that further announcements on the fifth HD slot on DTT are expected "in a few months", but potentially not until the start of 2012. Channel 5 HD is already available on Sky and Virgin Media.
The Freeview MD also noted that Sky offers considerably more HD channels on its platform (more than 50), but Freeview's four networks broadcast the vast majority of shows people actually watch in HD (apart from sport).
> Subscription-free satellite service Freesat tops 2m sales