Which sources are canon and non-canon?
Canon
Everything released by Blizzard except mods and the table-top RPG is considered canon.[1] This includes
games, novels, short stories, manga, and comics[1][2] as well as trailers and cinematics. Warcraft Encyclopedia, History of Warcraft, game manuals and original Warcraft RTS games are also considered canon but in some cases they are overwritten or modified by novels (i.e. history of eredar retconned in Rise of the Horde, War of the Ancients and its aftermath slightly altered by the time-travel in the novel, Dawn of the Aspects revealing the true history of the Aspects instead of a legend told in a History chapter, and Tides of Darkness with Beyond the Dark Portal setting a canon line of events for the first RTS games which had two versions of the ending).
The current history of Warcraft was slightly retconned by the WoW Chronicle series.[3]
No longer available quests that were not replaced by new information should be canon.[4]