A specific type of Alternate Continuity
in which the two continuities diverged off from a previous installment in the franchise. The two continuities are mutually exclusive, but both canon. They share identical backstory, but the outcomes of the story in either continuity may turn out very differently. Often caused by Time Travel
- Explained in-story in Star Trek. The two Star Trek timelines diverge at Kirk's birth. In the Prime timeline, Kirk is born on earth and the timeline proceeds how you remember it. In the new timeline, Kirk is born in space, his father is killed by Nero, and Vulcan is eventually destroyed.
- The Legend of Zelda has one, caused by Link's time traveling in Ocarina of Time. In one continuity, Link defeats Ganon and goes back in time. Then, Ganon rises again, causing Hyrule to be flooded. The Wind Waker follows this timeline. In the other continuity, Ganon never takes over Hyrule in the first place, and is banished to the Twilight Realm because Link warned the king about his treachery. Majora's Mask and Twilight Princess happen in this continuity.
- The Marvel Universe has tons of divergent "What If?" stories, but the Spider-Girl series takes place in the MC2 universe, which diverged from the main continuity after the Clone Saga. in this continuity, Spider-Man's daughter survives and becomes Spider-Girl in the future.
- Terminator has the main continuity, in which Judgment Day happens and John Connor leads the resistance in the future. The Sarah Connor Chronicles happens in an alternate timeline where Judgment Day was prevented.