Every expression of D&D has its own canon.
Our studio treats D&D in much the same way that Marvel Studios treats its properties. The current edition of the D&D roleplaying game has its own canon, as does every other expression of D&D. For example, what is canonical in fifth edition is not necessarily canonical in a novel, video game, movie, or comic book, and vice versa. This is true not only for lore but art as well.
This approach allows R.A. Salvatore to write Drizzt novels without having to worry if his version of the Forgotten Realms perfectly matches what we do in the roleplaying game. It means that a D&D video game can take elements from a series of novels and present them in a way that serves the game’s needs, rather than adhering to the sequence of events chronicled in the novels. Creatively, it’s liberating. This approach also acknowledges that different media have unique challenges and requirements.
Every edition of the roleplaying game has its own canon as well. In other words, something that might have been treated as canonical in one edition is not necessarily canonical in another. For example, the succubus was classified as a devil in fourth edition, even though it had been a demon in previous editions.
It can also be said that every campaign that’s ever been run in any of our published settings has its own canon. Your version of the Forgotten Realms has its own canon, which doesn’t make it any less valid than anyone else’s version. Elminster might be a lich in your Forgotten Realms campaign. Elminster might be a miniature giant space hamster in mine—both are acceptable and awesome.
Key to our approach is the belief that the story belongs to the DM and the players, not us. We make a conscious effort to preserve as many opportunities as possible for DMs to play with their own ideas. That’s why we don’t produce sourcebooks that spool out a ton of backstory. The DM or player remains the ultimate arbiter of what’s true in their expressions of D&D.
Source: Dungeons & Dragons