Series 1-6 of Big Brother (2000-2005), including the four series of Celebrity Big Brother in between, were some of the very few programs on mainstream British terrestrial television that were broadcast in the old 4:3 aspect ratio as opposed to the more common 16:9 wide-screen format. (Except the Big Brother Panto, which was in wide-screen). The reason for this is unclear, but was believed to be because of the size of some of the hidden cameras. However, from Big Brother 7 (2006) the aspect ratio has been switched in favor of the 16:9 format, with Big Brother, and all of its sister shows, broadcasting in wide-screen.
The action from within the house is streamed live over the Internet for a one-off fee subscription that lasts until the end of a series. Since the second series Channel 4's sister station E4 has also carried live pictures and audio from the Big Brother house. However the stream had a delay of 15 minutes so that audio and/or pictures can be edited out to comply with TV regulations.
Following the end of Big Brother 7, 156 house-mates have inhabited the house (not including the 8 participants in Teen Big Brother). 33 of those were celebrities, including Chantelle Houghton, the non-celebrity contestant in Celebrity Big Brother (2001) series 4.
Each year Big Brother is a ratings winner for Channel 4. The final of Big Brother 3 on 27 July 2002 was watched by 10 million viewers, the highest ever ratings for a non-film on the channel, and BB3 as a whole averaged almost 6 million viewers. Big Brother 6 had an average of 4.4 million, the poorest in the show's history. BB7 was ahead of it, averaging 4.7 million viewers. However the finale of Big Brother 7 at its peak reached 8.2 million viewers.
In BB7, Dawn Blake became the first contestant to be ejected for having contact with the outside world. Dawn organized a special code with her family: if there was any bad press regarding her, then their family would tell Big Brother that her sister was ill. Dawn received this message and informed the other housemates of this code.
Series 7 was the first series to allow a random member of the public to enter the house. 100 golden tickets were placed in Kit-Kat chocolate bars, granting the finder a chance to enter the Big Brother house. Of those tickets, 58 were found before the deadline, but two people decided not to put themselves forward for the show, three dropped out, and 19 did not pass the required background checks, leaving a total of 34. The competition began at 10:30pm on May 18, 2006, the launch date of Big Brother. Susie Verrico became the "Golden Housemate" after being randomly selected in a Bingo style machine, as each ticket-holder were randomly given numbers to wear as hats and armbands on the day.