Canon refers to the body of work within the Harry Potter universe. When it comes to canon for the series on the Potterpedia wiki, there is one rule - if it can be proved to have originated from Rowling, then it is law. More specifically, anything that directly originates from the Harry Potter books is considered canon on this wiki. Material from other projects, such as the films or games, may only be considered canon if it is known to have been directly developed and endorsed by Rowling. Material from Rowling's official website and Pottermore is also considered canon. In cases where Rowling has contradicted herself, her most recent statement regarding a matter shall be taken as canon, unless there is good reason to consider that it does not fit accurately with other given canon information.
In the case of any confusion, material from the novels will always be treated as primary canon. If an issue is ambiguous, then only what is known from the novels will be credited.