Canon can be split into three categories, "Canon", "Non-Canon", and 'Anime Campaign".
Canon
Canon is the Epithet Erased Show and Novels, as well as any supplementary media that does not contradict it. If there is a contradiction in canon (ex: Meryl also being on dispatch in EP 5-7 Novelization contradicts the conversation in "Redwood Run" between Percy and Eros), we would find a solution to amend it whether it's ignoring one, acknowledging both whenever it appears, or finding a less than obvious to make both true.
Unknown Canon
In cases where a piece of media's canonicity is unclear, it is assumed to be canon. That is a piece of media that does not contradict the Canon media but is not confirmed by Brendan Blaber (or another crew member) or by Canon media itself.
Non-Canon
Non-Canon is any media said to be non-canon, like TWO-LOWEEN, or can't be Canon due to contradicts, like the ads involving the Epithet Erased dolls. Although information revealed in them may be taken as canon (at least in the case of TWO-LOWEEN where it was said to be the case) but not the main events of the story.
Anime Campaign
Anime Campaign Canon is the Canon of Epithet Erased's source material, Anime Campaign. This wiki will only cover re-released episodes.