One end of the Rift was located in the Cardiff area, said by Rose Tyler to run straight through the centre of Cardiff. (TV: Boom Town) When the Rift fractured, it temporarily spread out from Cardiff to cover parts of the entire Earth, including London and Tokyo. (TV: End of Days)
The other end of the Rift varied, and encompassed various times (TV: Out of Time, End of Days, To the Last Man, AUDIO: Asylum) and places. (TV: The Unquiet Dead, End of Days, Meat, Adrift) According to Vox, the Rift had many openings, particularly in the Sanctified's area of their galaxy. (COMIC: Rift War!)
Travel through the Rift
When the Rift became active, beings and objects could be transported through Rift flares either from one end of the Rift to another, or to another point in time on the same end of the Rift. Rift storms were also capable of transporting objects and beings caught up inside of them through the Rift. (TV: Kiss Kiss, Bang Bang, COMIC: Rift War!)
The Rift could cause time shifts, which could cause two different points in time to overlap and could transport beings from one of the two overlapping times to the other. (TV: Captain Jack Harkness, To the Last Man)
Some extraterrestrials were also known to be able to manipulate travel through the Rift, as the Weevils could use the Rift to cross into Cardiff, and the Sanctified were able to transport their Harrowkind troops through the Rift and could create and manipulate Rift storms to transport wanted objects through the Rift to them. (COMIC: Rift War!)
The Rift several times displayed traits similar to those of a living or sentient creature. For example, the Rift would sometimes after a length of time return those it abducted from Cardiff, which Jack Harkness believed was an attempt by the Rift to correct its mistakes and the damage it was doing. (TV: Adrift) Also, when Vox attempted to absorb the power of the Rift, the Rift sent antibodies to eliminate Vox. (COMIC: Rift War!)
Prison of Abaddon
During Abaddon's and the Light's war against Pwccm and the Dark, both sides eventually became caught up in and trapped within the Rift, although they could escape the Rift and fight when it was opened wide enough. (PROSE: The Twilight Streets)
The Gelth's use of the Rift
Following the Last Great Time War, the Gelth attempted to flee through the Rift to 1869 Cardiff, but initially, only a few of the Gelth were successful in travelling through to Cardiff. Using a psychic named Gwyneth as a bridge through the Rift, the Gelth successfully began to come through into Cardiff and tried to invade Earth and kill off the entire human race and use their corpses to become corporeal. During the Gelth's attempted invasion, Gwyneth was able to trap the Gelth already on Earth inside and close the Rift. (TV: The Unquiet Dead) The closing of the Rift left behind a "scar" which released energy. On his first visit to Cardiff, Jack Harkness considered this radiation "harmless" to humans, but viable as a power source that the Doctor's TARDIS could "soak up". (TV: Boom Town)
Torchwood Institute's interest in the Rift
Around the turn of the 20th century, the Torchwood Institute became aware of the Cardiff Rift. Agnes Havisham believed it was a threat and helped set up Torchwood Three to study it. (PROSE: Risk Assessment)
Located in an underground base called the Hub and under the command of Captain Jack Harkness, Torchwood Three had the tasks of monitoring the Rift and phenomena associated with it and with securing for Torchwood any artefacts that came through. (TV: Everything Changes et al) The Hub also possessed a Rift Manipulator which allowed them to control the Rift to a limited extent. (TV: Captain Jack Harkness, End of Days, COMIC: Rift War!)
The widening of the Rift
The Rift was used in September 2006 by both the Ninth Doctor to power up the TARDIS from the energy released from Gwyneth closing the Rift, and by Blon Fel-Fotch. Blon Fel-Fotch, then mayor of Cardiff, plotted to cause a core meltdown with the Blaidd Drwg nuclear power plant. The meltdown would have destroyed the Earth, generating a shock wave that she could ride to escape off into space using a tribophysical waveform macro-kinetic extrapolator. The extrapolator, connected to the Doctor's TARDIS, accidentally widened the Rift and caused a powerful earthquake. (TV: Boom Town)
The fracturing of the Rift
In early 2008, Bilis Manger contrived to trick Torchwood Three's Owen Harper into using the Rift Manipulator to widen the Rift on purpose. This caused the Rift to fracture, resulting in time slips worldwide. Many believed the end of the world had come. (TV: Captain Jack Harkness, End of Days)
In Cardiff, more Weevils came through the Rift, as well as a Roman soldier and sufferers of bubonic plague. Finally, as Manger had planned, the Rift opened wide enough for Abaddon to escape. Jack stated that the area would become more active after the opening of the Rift and the death of Abaddon. (TV: End of Days)
Later uses and discoveries
The Rift caused an overlap in time between 1918 and 2008, creating the illusion of "ghost sightings" in both times. The time shift was initially confined to a Cardiff hospital, but as it worsened it quickly spread out throughout the city. Torchwood Three sent a cryogenically frozen soldier from 1918, Tommy Brockless, back from 2008 through a time hole with a "Rift key", and he was able to close the hole. (TV: To the Last Man)
The same year, Gwen Cooper discovered an unknown property of the Rift, that it abducted people from Cardiff as well as depositing creatures and objects from the other sides. She found out that a number of missing people could be connected to the activity of the Rift. (TV: Adrift)
The Rift war
The Sanctified used the Rift's energy to power their empire. In 2008, when the Sanctified were led to believe that Torchwood Three would use their Rift Manipulator to destroy their empire, the Sanctified declared war on Torchwood and used the Rift to send their Harrowkind troopers to Cardiff to attack Torchwood.
Vox hid from the Sanctified in the gaps and non-places inside the Rift, until Toshiko Sato unintentionally led the Harrowkind to Vox when she and the Torchwood Hub became one moment out of sync with time as a result of a Rift storm. Vox subsequently returned with Tosh and the Hub to Cardiff.
Vox subsequently used the Rift Manipulator and alien technology to absorb the power of the Rift, which caused the Rift to produce antibodies and send them to Cardiff to try to eliminate Vox. When Torchwood Three restored a natural focal point for the Rift's energy which Vox had previously destroyed, the focal point became a new outlet other than Vox for the Rift's energy, and thus Vox lost the Rift's power. (COMIC: Rift War!)
Contacting the Doctor
In the year 2009, when Earth was transported by the Daleks to the Medusa Cascade, the Rift seemed to move to there with Earth. Jack Harkness, Gwen Cooper, and Ianto Jones of Torchwood Three used the Rift's power via the Rift Manipulator in conjunction with Sarah Jane Smith's supercomputer, Mr Smith, to power a message to the Doctor via Martha Jones' superphone. (TV: The Stolen Earth) They later used the combination of the Rift and Mr Smith again to help the Doctor return the Earth back to its regular orbit. (TV: Journey's End)
Use by other extraterrestrials
The Weevils used the Rift to cross over into Cardiff for reasons of their own, more so as the Rift de-stabilised. (TV: Everything Changes, Combat, End of Days) The Sanctified Empire were also known to harvest energy from the Rift, and used it to send their Harrowkind troopers to their intended destinations. (COMIC: Rift War!)
Behind the scenes
The closing of the Rift
There are two different sources on how the Rift closed. According to AUDIO: The House of the Dead, the Rift finally closed when the House of the Dead was destroyed. However, this is contradicted by Russell T Davies, who stated that the Rift closed with the Cracks in Time when the Eleventh Doctor rebooted the universe.  As none of Davies or his production team's scripts, as of 2014[update], have narratively contradicted Dead, this wiki only considers Dead a valid source as to how the Rift was closed.
A file on the series 1 version of the Torchwood website says that one end of the rift is fixed, ±5 miles from Cardiff Bay, while the other end is "wandering in a seemingly random progression across the universe". Though it notes Rift activity has increased since the "recent" Cardiff Earthquake, it notes that after the events in December 1869, the Rift has not been quiet. 
The series 1 version of the Torchwood website had a letter home dated 92 AD addressed from the soldier Q. Asinus Balbus to Ti. Marcus Musca. Toshiko Sato noted it had "interesting references". It said that the girls who hang around camp brought back messages of a "terrible god" beneath that land that became restless and hungry. When Balbus went on an expedition to the territory, he found entire empty villages along the shore. After hearing what sounded like "the howling of a giant beast", Balbus headed back to camp. By the time the expedition made it back, three of the patrol were "lost". Despite not hearing or seeing anything, the rest of the group "knew" that they were being "melted away", and carried on, knowing they could do nothing about it. 
The series 1 version of the Torchwood website features a speech from Queen Victoria, calling the Rift a "chilling" example of what the British Empire can "only" be defended from. She was concerned how the Empire could protect against a "border" like the Rift and how anyone can be safe if "unimaginable demons" could step through the rift at any moment. She claimed that the Rift need "[v]igilant, tireless and fearless" guardians to protect the "infinite shores" of the Empire. 
The series 1 version of the Torchwood website had a "rift memo", dated 13 April 1913. It alerted the "chief" that on that day there was a sudden increase in Rift activity that manifested as "a series of small ground tremors". It was concerned about Robertson's conclusions from the data: it seemed to be a ripple from a "much bigger" event, or "[an] aftershock washing back to towards us through time – call it a preshock, if you will." Robertson calculated that it orginated at some point in the 21st century. The memo claimed that Cardiff has "got about a century to go before the rift tears it apart." It said it "might be an idea" to increase safeguards on the rift manipulator. 
- ↑ More Torchwood Updates. Blogger - The Doctor In The TARDIS (29 July 2010). Retrieved on 25 July 2013.
- ↑ The Rift. Torchwood website. Archived from the original on 26 August 2007. Retrieved on 25 July 2013.
- ↑ Balbus, Q. (92 AD). Roman letter. Torchwood website. Archived from the original on 26 August 2007. Retrieved on 25 July 2013.
- ↑ Queen Victoria (August 1883). Queen Victoria on the Rift. Torchwood website. Archived from the original on 27 August 2007. Retrieved on 25 July 2013.
- ↑ End of Days - Rift memo, 1913. Torchwood website (13 April 1913). Archived from the original on 27 August 2007. Retrieved on 25 July 2013.