Games Workshop 'canon' is often quoted in many a forum argument, and while many game universes do have a strict canonical source that can be quoted as 'fact', 40K seems to have a very liberal view of what 'canon' is and how the background books, novels and 'colour text' should be viewed.
This quote is taken from the Black Library forums FAQ
Is Black Library fiction canon background material?
"The BL editors work with the GW studios to keep the fiction the way that it should (very hard might I add! - RK), though due to the sheer volume of detail involved there can be the odd discrepancy here and there. If you want to consider anything "canonical" then both BL fiction - be it novel, graphic novel, art or background book - and GW fiction - be it White Dwarf, Codex, Army book or rulebook - are such.
Keep in mind Warhammer and Warhammer 40,000 are worlds where half truths, lies, propaganda, politics, legends and myths exist. The absolute truth which is implied when you talk about "canonical background" will never be known because of this. Everything we know about these worlds is from the viewpoints of people in them which are as a result incomplete and even sometimes incorrect. The truth is mutable, debatable and lost as the victors write the history ..."
My take: As I understand it, is that there is no strictly 'canon' background and it's all down to interpretation. In addition the Black Library uses an extended or expanded version of the 40K background and the Wargame uses are restricted background. To really tidy up this concept;
Quote taken from the Old Black Library Forum thread: The question of "canon"?
"I think the real problem for me, and I speak for no other, is that the topic as a "big question" doesn't matter. It's all as true as everything else, and all just as false/half-remembered/sort-of-true. The answer you are seeking is "Yes and no" or perhaps "Sometimes". And for me, that's the end of it.
Now, ask us some specifics, eg can Black Templars spit acid and we can answer that one, and many others. But again note thet answer may well be "sometimes" or "it varies" or "depends".
But is it all true? Yes and no. Even though some of it is plainly contradictory? Yes and no. Do we deliberately contradict, retell with differences? Yes we do. Is the newer the stuff the truer it is? Yes and no. In some cases is it true that the older stuff is the truest? Yes and no. Maybe and sometimes. Depends and it varies.
It's a decaying universe without GPS and galaxy-wide communication, where precious facts are clung to long after they have been changed out of all recognition. Read A Canticle for Liebowitz by Walter M Miller, about monks toiling to hold onto facts in the aftermath of a nuclear war; that nails it for me.
Sorry, too much splurge here. Not meant to sound stroppy.
To attempt answer the initial question: What is GW's definition of canon? Perhaps we don't have one. Sometimes and maybe. Or perhaps we do and I'm not telling you."
So that's an unofficial answer on what 'canon' means to the Cruel Overlord of the Black Library, which is very much a part of Games Workshop. There is also this fun thread where I manage to chip in a few thoughts on the subject of canon in: Canon or not (<-- now a dead link because BL keep changing their forum and deleting everything!).
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