Goofs

The janitor at S.T.A.R Labs is wearing an ID badge of someone else in his first scene, and then his own in his second scene.

As Bruce talks to Barry about joining the Justice League, Barry's hairstyle changes.

After saving the fisherman, Arthur gets a glass of whiskey and notices green goo on his hand and glass. In the next shot, the goo is no longer on his hand nor the glass.

During the gang's discussion about Superman and the Mother Box, Arthur wears the same coat he ditched in the village.

When the Russian family's home is first shown, there is a small moped outside. In the next scene, the moped is now a large motorcycle.

A powerful bomb that is about to destroy four "city blocks" from inside a bank, does not explode harmlessly just above the roof of that bank.

In the beginning of the film as the opening credits show, one store in the city has the sign reading "stationary". The correct spelling is stationery.

When the Flash/Barry Allen is going undercover into S.T.A.R. Labs as an Air Force MP, and Cyborg/Victor Stone hacks the computer to give him clearance, he puts his date of birth as 11/06/10. This would make him 7 years old. He wouldn't quite meet the age requirement for the military if that were the case.

A grave is typically six feet deep. Even allowing for the thickness of the coffin, Cyborg and The Flash should have had to dig much deeper before their shovels made contact with the lid.

In real life, Hippolyta's cape would have been caught in the collapsing gate as she slides under it.

In the Tunnel fight scene, before Flash starts saving civilians, Flash states how he is afraid. This should have attracted the parademons since they can smell fear, but given multiple civilians much closer to parademons and much more afraid than him, it's perfectly reasonable to assume that their fear was overwhelmingly stronger and completely masked Flash's fear.

It is claimed by Cyborg that the mother box came to life after Superman was killed in the events of Batman vs Superman, however in the video that Wonder Woman watches during BvS it can be seen as reacting and creating Cyborg. However, it created Cyborg in lab conditions and could have been artificially activated similar to how the Flash activated it in this film.

When Batman is driving the batmobile one of the flying aliens rips the cannon off of the batmobile and starts to smash the batmobile with it. However later when Aquaman is standing on the batmobile the cannon is still attached. Actually the creature tore off one the smaller machine gun barrels to destroy the other one. The bigger cannon that Aquaman is standing next to fires much heavier ammunition and was never destroyed.

Near the beginning, when Wonder Woman uses the "Lasso of Hestia" to compel a man to tell the truth about who he and his compatriots are, he replies "we're a small group of reactionary terrorists". Terrorists usually think of themselves as freedom fighters, patriots, warriors of God etc., not terrorists. However, not every terrorist is a true believer, becoming a member of a terrorist group for other reasons (greed, revenge, confusion, coercion, etc.), and even true believers can feel the error of their ways deep down, not even admitting that to themselves until the Lasso compels them to.

When the Flash goes undercover to sneak into S.T.A.R. labs, he is wearing an Air Force uniform with one stripe on his sleeve. He then hands his military I.D. card to the guard who then scans it. After scanning, the computer screen displays information indicating his pay grade is E7. An E7 in the Air Force would have six stripes on his sleeve, not one stripe. However Victor who is hacking the system to grant Barry access is still figuring out his powers and as the team are on a time limit it's so he just picked a random rank that would allow Barry to enter a top secret base.

Most of Superman's scenes feature a poorly animated CGI lip in closeup shots. This was because Henry Cavill was filming scenes for Mission: Impossible - Fallout (2018) (in which his character has a mustache) simultaneously with re-shoots for this film. He was contractually prohibited from shaving his mustache and his scenes were filmed with it. Because of a tight production schedule, there was little time to properly apply CGI in post-production, leaving the results painfully obvious.

The Amazons trying to prevent Steppenwolf from grabbing the Mother Box merely have his hands on him; they are not grasping his garments or pulling on him.

Flipped shot: When Cyborg tries to hack the Nightcrawler, the writings on the panels etc seem to be in reverse.

When the Amazonian Queen fires the flame-arrow her hand keeps moving back but the front of the arrow doesn't move along, making it appear as it the arrow is stretching.

Obvious studio shot of Arthur standing in the water as he talks to Bruce, as evidenced by poor chroma-keying and color correction.

When he meets Barry, Bruce describes Barry's costume as being made of the same material used by the space shuttle during reentry. This does not correlate with the suit as shown. The material on the shuttle is made of feather-light ceramic that is easily damaged by impacts and it cannot work properly with a painted surface as is seen in the costume.

Another issue with the costume is that it is wildly irregular and in such a way that it would cause extreme wind resistance and catastrophic turbulence at lightning-fast speeds.

It's been established there are aliens from other worlds on Earth, yet the man who reports on the woman who claims her husband was abducted by aliens does so in a smug, condescending manner.

While the gang discusses Superman and the Mother Box, Aquaman swipes something off of the table, but we never learn what it is.

When Lois Lane tells Clark Kent, "You smell good", her lip movements do not match up. This was because she originally said, "You spoke", which was overdubbed for the theatrical release. The original line was subsequently reinstated in Zack Snyder's Justice League (2021).

When Cyborg says "I don't even understand the physics of how my toes hurt", his lip movements are badly mismatched.

The Parademons are shown to have super strength (as, for example, they ripped off parts of the Batmobile and they easily caused it severe damage), but they were attacking the Russian family's house (which has a very poor structure) for a long period of time and they couldn't even storm in.

Steppenwolf finds two of the boxes with ease, so needing the Parademons to find the third box makes no sense.

The Atlantean "A" symbol is on Arthur's suit, signifying his acceptance by the Atlanteans as their king, yet he does not wield the Trident of Atlan. Without the Trident of Atlan, Arthur is not King of Atlantis.

During Wonder Woman's rescue of the hostages in London one of the terrorists, who is clearly British, says the bomb will destroy four city blocks. The term city block is not used at all in the UK.

Cyborg tells Gordon: "The lines on the map don't converge. On land. These lead back to Stryker's Island". An island is land, the lines do converge in the bay, and Stryker's Island is clearly seen on the map.

As she talks to Lois about Clark, Martha references his superpowers within earshot of everyone in the newsroom.

The Parademons attacking the fishing boat makes no sense.

After speaking with Gordon, Batman, Wonder Woman, and Cyborg "vanish" and the Flash is taken by surprise by this. The Flash would have easily seen this and departed at the same time they did.