An alter vu is the feeling of either remembering something differently, or experiencing visions or dreams of events that never happened, allegedly as the result of changes to a worldline.
The term alter vu is primarily associated with the alleged time traveler John Titor, who first began posting online under the forum handle TimeTravel_0 at the Time Travel Institute (TTI) on November 2, 2000.
After Titor stopped posting on March 24, 2001, several forum users shared their experiences with strange memories and feelings that their current worldline had somehow changed. Many of these same users had previously sent Titor private messages, which he agreed to take back with him on his temporal trip to 1998 and deliver to alternate-worldine versions of themselves.
Pamela, a prominent figure of the John Titor story, claimed to have had a dream in April 1998 about a time traveler visiting her in a car. It wasn’t until Titor’s appearance in 2001 that she remembered, and found the description of that dream in her dream diary.
This dream, she believed, may have been an alter vu, a vision from another worldline in which Titor had visited her in 1998 to deliver her message from 2001.
The term alter vu may have itself been coined by TTI poster Florida_Jim, in an attempt to describe “awareness of the changes” to a timeline.
Alter Vu Vs. Mandela Effect
Alter vus may be similar to the Mandela Effect. However, a difference may be drawn: While the Mandela Effect is said to occur when people notice a detail in their history (or knowledge) that now seems different from what they once knew (for example, in the case of the Berenst#in Bears Problem), an alter vu generally seems to be a much more personal experience.
In particular, the cases of alter vu described above happened to individuals with knowledge that they may have affected a different worldline through their own actions (by sending a message to the past of an alternate worldline) or though the actions of someone they’ve interacted with (in the case of John Titor).