Since there are different sources of information for Harry Potter canon and sources do, on occasion, conflict with one another, the following guide is to be used on the Harry Potter Wiki. In order to simplify the different areas that exist as sources for canon information in the Harry Potter universe we have devised a three tier system summarised below. Please remember any type of fanon, information created by fans using the Harry Potter characters, is not considered canon at all and must be marked as such, unless made canon by a legitimate source.
Although there are different levels of canon, this does not mean relevant information cannot be included in situations where there are conflicting canon sources. Ambiguous continuity should always be noted. If an "official" canon source has been chosen, (e.g. J. K. Rowling has said that a fact was a mistake and it was meant to be something else), the information from the conflicting source should still appear in the article in the "Behind the scenes" section.
Basically put, everything is canon unless specifically contradicted by a "higher" source.
- JKR - These sources come from J. K. Rowling herself. When J. K. Rowling contradicts herself, the newest source is to be taken as the "most" canon.
- Other writings by Rowling set within the Harry Potter universe, i.e. the Harry Potter Prequel short story.
- J. K. Rowling's Official Website
- Harry Potter and the Cursed Child 
- JKR Involved - These sources do not contain information directly from the "mouth" of J. K. Rowling, yet they are projects in which she was involved.
- JKR Licensing - These sources are where J. K. Rowling licensed the use of the Harry Potter universe to another company or individual.
Examples of usage
- Oliver Wood mentions in the Philosopher's Stone film that he took a Bludger to the head in the first few minutes of his first ever Quidditch game. This is never mentioned in the books. Is it canon according to our guide? Yes, since there is no evidence from the books to say that it didn't happen. Whatever the quidditch team were saying just before the game started is not mentioned in the book but it is shown in the film. So the fact that Wood told harry about it is also canon too. If the book explicitly told us what harry did just before he did Quidditch (E.G Fred and George talking about Bludgers) and that Wood never told him anything about being hurt, then wood telling Harry wouldn't be canon but what happened to wood in the past would be canon.
- The Harry Potter games contain a spell known as Avifors to change statues into birds. Is this canon according to our guide? Yes, since there is no evidence to suggest that such a spell doesn't exist. This can generally be applied to most spells/items from the games.
- In the Goblet of Fire film, Krum attacks Fleur in the Maze during the Triwizard Tournament. Is this considered canon? No, because the book, a higher source of canon, specifically states that Crouch/Moody did it. However, it should be noted in the "Behind the scenes" section.
- Mafalda is a cut character from an early draft of Goblet of Fire. Is she canon according to our guide? Yes and no. The fact that she exists may be considered canon, but anything about her intended part in the story cannot be considered canon because it did not happen in the books. Her physical appearance would be canon, and any particular traits, skills or personality expressed by her omitted lines would be part of her character.
- In the games, are the various challenges/levels considered canon according to our guide? Yes and no. Levels like the Glacius Challenge from the Prisoner of Azkaban game should not be considered canon since it is highly unlikely that the students would be put in danger like that. However, challenges like helping to assemble Dumbledore's Army for their first meeting in Order of the Phoenix could conceivably be considered canon because they usually involve helping out with a task to free the student up to attend.
- The millennium bridge being destroyed in the Half Blood Prince Film is not contradicted in the books so it is canon.