A fan's unverified beliefs about a story
In my headcanon, Peter Parker was totally that little boy Iron Man saved in Iron Man 2. It just makes sense.
|Fandom||Community of fans|
|Superfan||An extremely dedicated fan|
|Shipping||Hoping for two people to get into a relationship|
|Fanboy||A dedicated male fan|
|Fangirl||A dedicated female fan|
|Hot take||A controversial opinion|
Headcanon means "a fan's unverified, unique beliefs about a story they love." Superfans of many media properties (most often, comics, TV shows, and novels) maintain a headcanon that supplements the property's official story.
For example, for much of the TV show Adventure Time's run, many fans' headcanon maintained that Princess Bubblegum and Marceline were (or had been) romantically involved. After dropping several hints implying these fans were correct, the show made Bubblegum and Marceline's relationship canon in its final episode.
Many fans' headcanons are related to the ships they support, but headcanons are also used to explain away non-sensical story points and fill in blanks about characters, locations, and lore. If you've ever assumed you know what a character's favorite food would be or what kind of car they'd drive, you've begun creating your own personal headcanon.