Justice League Snyder Cut is NOT CANON to the DCEU. None other than Zack Snyder, the brainchild of Justice League Snyder Cut, acknowledged this fact that his version of the film is not canon to the DCEU while the 2017 theatrical release of the film, the version of Joss Whedon, is the one that is canon.
Justice League Snyder Cut is called for by various fans of DCEU rattling on the internet #ReleaseTheSnyderCut for years and after quite some time, it is finally seeing the light of day as the film arrives in a few days.
To say the least, Justice League Snyder Cut is a totally different film from the theatrical release of the film in 2017. Joss Whedon's Justice League reportedly only has about 10% to 15% of the shoots done by Zack Snyder and almost all the storylines and arcs were changed making the film into something that is far from what the original director had in mind.
From the tone of the film, to the runtime, to the storyline, Justice League Snyder Cut and Joss Whedon's Justice League are completely different from each other. (You may see all the notable differences between the two films in this link.)
Joss Whedon's Justice League sets up the stage for various DCEU films that followed the film making it canons such as Aquaman in 2019, Shazam! in 2019, Birds of Prey in 2020, and Wonder Woman 1984 in 2020. Given that the Justice League of Joss Whedon is the Warner Bros. produced same as the previously mentioned films, it stands to be the canon film of the DCEU.
Zack Snyder left mid-production after not being able to sort out his creative differences with Warner Bros. which explains why the film is unlike what the director had in mind. Now that he has been given the avenue to show his version of the film, fans calling for #ReleaseTheSnyderCut clearly achieved their victory.
In a recent interview of Snyder in the podcast DC Cinematic Cast, the four-hour Justice League Snyder Cut still stands canon with his previous films Man of Steel (2015) and Batman v Superman: Dawn of Justice (2016), however, when it comes to the films released by DCEU afterward, what holds canon is Joss Whedon's Justice League.
Snyder said, "Canon for Warner Bros. is the Joss Whedon version of Justice League, right? That's—in their mind—that's canon. And what I'm doing is not, everything I'm doing is not."
It has been years since the release of Joss Whedon's Justice League and much of the DCEU fanbase still doesn't accept the film to be canon even when the story of the film has a continuity with the films that succeeded it. It was also revealed in an interview with Wonder Woman director Patty Jenkins that even the DCEU directors have the same regard for the film as the fans as they don't consider the film canon as well.
Canon or not, the clamor of the fans were still given respect and now that the Snyder Cut is only a few days away from release, Snyder says that he understands the frustration of the fans as he is, too, but then again, it's not his call to take, not his decision to make.
It's not everyday films like this that get the chance of seeing the light of day, a great example is the Ayer Cut of the Suicide Squad. Many other films don't get the chance Snyder Cut has right now and the clamor of fans standing firm on their side calling for the release of the picture the director originally has in mind.
The humility of Zack Snyder in accepting that his version is not canon mirrors the reality that sometimes, things do not go the way we plan for them to be. There would be times that things would go sideways or times that it would not be part of the bigger picture but that doesn't mean it shouldn't be given a chance.
Despite all these, it's safe to say that upon the release of the Snyder Cut, we all should just take it in and breathe at the moment that despite the overwhelming odds the film has gone through, it's here, it's finally here, canon or not, it is finally arriving.
Justice League Snyder Cut premieres on HBO Max at 2 AM EST. (release time will be different for various locations) The 4K Ultra HD DVD/ Blu-Ray release of the film will be between March to April 2021.