Headcanon is when the fans use their owm interpretations of a or over a fictional universe that they find accepted to themselves as a fan, but yet its not entirely found within or supported by the official canon source material.
Headcanon is basically another word for Fanfic because its a fan using their own canon and not the official established canon as a source material.
Please take notes that this is not them using actual researcyed Theories since these are what they believe to be canon fact within the series, its more or less them using actual fan logic aka Fan Theories.
- False Canon: Headcanon: "Classic Infinity Gauntlet is Multiverse level!
- Canon: Canon: Infinity Gauntlet only works inside its native universe.
- False Canon: Headcanon: "Pre-Retcon/Cosmic Cube Beyonder isnt Omnipotent."
- Canon: Canon: Beyonder is Omnipotent by Marvel.
- False Canon: Headcanon: "Goku once almost destroyed the macrocosm! So he should be atleast Small Universe+ level because we said so!"
- Canon: Canon: Goku hasnt even once destroy a planet,solar system,galaxy or a Universe.