List of inconsistencies in the Halo series

This list is compiled to show the various discrepancies spotted in the Halo universe. It is difficult to decide which resource is "superior" to another, so usually, the inconsistency is mentioned in the articles that it involves.

If you think you can explain an inconsistency, do so here, on the article's talk page.

There are two types of inconsistencies: Conflicts and Discrepancies. Conflicts happen when two sources disagree about a situation, subject or object. Discrepancies occur when a seemingly impossible event happens without any explanation.

Halo: The Fall of Reach

 * On page 46, Kelly handed out parts of a map to the seventy-five SPARTAN-II trainees. Then on page 48, when John checked to make sure the children arrived at the lake, he counted only sixty-seven...which seemed to be all of them.
 * The London was included as a mistaken reference to the UNSC Pioneer in some early editions.
 * A UNSC frigate was referred to as the UNSC Alliance, and then shortly thereafter as the UNSC Allegiance.
 * The ship UNSC Leviathan is referred to as a cruiser and then later as a carrier.
 * On page 19, Michael Stanforth was said to be a Vice Admiral, and on page 95, it said he was a Rear Admiral. It is very rare for the brass to be demoted because they achieve a lot in their rank.
 * James' left/right arm was burnt off by a Fuel Rod Cannon. However, he could easily have been given a flash-cloned arm after.
 * In 2552, Doctor Halsey is only speculating the existence of the Elite race. Elites were encountered by humans before in the Battle of the Rubble (the First Battle of Arcadia) where the Spartan Red Team and Group Omega fought. They were also recognized by Kurt in a mission recording, and most importantly, the UNSC captured an Elite alive during the Battle of the Great Bear.
 * The Pillar of Autumn was missing its port-side emergency thrusters, but later used them twice.
 * Lieutenant Keyes had seemed skeptical when Dr Halsey mentioned that John-117 had luck, which meant he probably didn't believe in it (page 27), but later it mentioned Keyes taught his students how battles were won by luck as well as skill (page 212).
 * Captain Keyes refers to Ensign Lovell as "Michael" instead of "William", page 188.
 * While riding to Reach Station Gamma, Kelly-087 tells the Chief that the Spartans are "All secure." Kelly isn't even in the Pelican at the time. Either the author meant to say "Linda", or Kelly spoke on com...
 * During Master Chief's mission to Reach Station Gamma, a Jackal's blood is said to be blue while it is clearly purple. The same mistake is made with the Elites as well, saying that their blood is green, while it is dark blue.
 * It describes Lt. Hikowa as male, but then later refers to the lieutenant as female.

Halo: Combat Evolved

 * The Main view screen on the Pillar of Autumn labels the as-of yet unidentified ring as "Halo". The name of the ring is not discovered until the level Truth and Reconciliation
 * The view screen could have been referring to it by its shape, though the level of coincidence is unlikely.
 * This could simply be an easter egg
 * Cortana says she cannot begin to calculate the pulse range of Halo just after 343 Guilty Spark finishes telling her it has a radius of exactly 25,000 light years.
 * This can be accounted for by Cortana's inherent distrust of Guilty Spark's motives, though. Additionally, since Cortana is an AI with an insatiable urge to know everything she can, she may have tried to calculate the range herself regardless of whatever 343 Guilty Spark had simply told her.
 * She did not state she wanted to know the range, she simply stated she cannot calculate it.
 * Almost every Pelican dropship bears the marking of Foehammer's bird, "E419", on its side, despite the fact that each Pelican has a different ID number.
 * This doesn't excuse it, but Bungie only designed two models. They used the two to represent every Pelican.
 * Pvt. Jenkins' Record View on the level 343 Guilty Spark shows the date as the 27th of May 2552 when The Maw clearly takes place on September 22.
 * Frankie has confirmed that the date calibration of his equipment was not performed, causing the apparent discrepancy.
 * The pilot of the Master Chief's lifeboat is referred to as "Lieutenant", but says "Aye aye, sir" to the Master Chief, even though Lieutenant is a higher rank than Master Chief. This could be due to the fact that nearly all UNSC personnel owe subordinate respect to the Spartans to some degree.
 * John-117 had mission command and thus commanded all survivors, since his orders came directly from Captain Keyes, the commander of the entire operation. His mission was to get Cortana off the ship, and therefore he had tactical superiority.
 * There wasn't time before the Covenant invasion to spread this information throughout the crew.
 * "Combat teams Alpha through November..." How was it pronounced to the rest of the crew?


 * In The Maw, the main objective is to trigger a Wildcat destabilization of the Pillar of Autumn's fusion reactors. Later, Cortana tells Foehammer that the engine sustained more damage than she thought because of the Wildcat destabilization.
 * Note that this may be due to the fact that the engine decay rate was faster than Cortana originally anticipated, she theorized it must have taken damage on impact -- or, as is more commonly accepted, she didn't want to admit that they were blowing up the ship and made it up as an excuse.
 * Also in The Maw, the player has to travel over 3 kilometers atop the Pillar of Autumn to reach the Longsword fighter, but the Autumn is only 1.17 kilometers long.
 * This may be due to the route curving, detours, and other maneuvers increasing the distance. This is unlikely though, as the NAV marker does not account for such maneuvers and always points in the same direction. It adds distance when moving away from the objective.
 * The Longsword's launch bay in The Maw is also at the end of the Warthog run. The front or rear of a ship is an unlikely place to store a launch bay, which implies that Master Chief travelled from side to side. This makes even less sense than the Autumn suddenly being 2 kilometers wider.
 * In Halo: The Fall of Reach, Hikowa and Dowski are female officers of the Pillar of Autumn. However, on the level Pillar of Autumn, the bridge (HQ of a ship) has no female members.
 * Meaning that, like modern navy ships, the Autumn must have rotating shifts.
 * The only female model is the Lieutenant's, AIs don't have genders.
 * William Lovell's eyes are green, but the Autumn's crew has no green-eyed members.
 * Game designers do not generally colour the Iris. Instead, the game only shows the Pupil.
 * During the level "Assault on the Control Room", Staff Sergeant Johnson can be seen with the Chief at the time he was really with Captain Keyes searching for the Covenant's "weapon cache". Even though the Captain has been out of reach since The Silent Cartographer
 * Bungie was reusing Johnson's model instead of creating another Sergeant model.
 * In 343 Guilty Spark when John-117 arrives at the room, he finds Pvt. Jenkins' mission recording. As he opens the door a body collapses on him. This body should have been infected by the Flood.
 * It is possible he fought off the Flood only to die later of his injuries.

Halo: The Flood

 * The book consistently mistakes the 8-gauge shotgun as 12-gauge.
 * During a skirmish with a force of 100 Ghosts, the book describes how snipers and rocket-launcher-armed Marines couldn't be hit by plasma fire, as the Ghosts' weapons were fixed and the marines were on a hill. Yet in the game, the Ghost's plasma cannons can easily increase or decrease their angle. They could have easily killed the marines, unless they were positioned on an extremely tall and steep hill.
 * On page 101, it stated that "the Spartan was carrying a full combat load of ammo, grenades, and other gear, plus two magazines for the M19 launchers". The Master Chief was not carrying a Rocket Launcher at the time and if he was, he was never seen using it.
 * Two magazines, not the weapon itself.
 * It also illustrates that John ran out of ammo on his MA5B Assault Rifle, switching to an M6D Pistol but there are no pistols on that level at all.
 * Weapons in-game sometimes don't follow the ones written in the book, and stocks of ammo left behind by dead marines aren't mentioned either.
 * On the Truth and Reconciliation chapter, it describes that a Marine was killed and, "his rocket exploded harmlessly..." No Marines were seen wielding a rocket launcher on that, or on any other level.
 * Same as the above, but they don't have animations for holding a rocket launcher.
 * In the book it says that three weapons would be unwieldy for the Chief and not to mention "damn heavy." It then says he chose a shotgun and sniper rifle. Later,an Elite sliced his sniper rifle (presumably with an Energy Sword), prompting the Chief to draw a pistol. It was never explained how he obtained the pistol; however, its small size may have exempted it from the Chief's personal two-weapon limit.
 * Sergeant Parker is referred to as a he, and then a she.
 * Maybe it's just a simple typo.
 * Supposedly the Second Squad was completely consumed by the Flood, specifically saying that their numbers dwindled until two PFCs remained, before the last of the marines fell. A page later, however, Foehammer picks up the surviving Marines. This contradicts the other information, though it is possible that part of the second squad was separated, or that she didn't know second squad was entirely KIA.
 * First Lieutenant Melissa McKay's mission clock is prefixed by an extra 1. It should be noted that the last time it shows her mission clock, the clock reads D+144:38:19. Master Chief's last mission clock mention, it reads D+76:18:5 while he is en route to the Pillar of Autumn. It wouldn't take over 5 hours to detonate the ship, let alone 70 hours.
 * Near the middle of the book, Spec Ops Elite Zuka 'Zamamee lays a trap for the Master Chief near the Silent Cartographer, coinciding with the game level of the same name. Afterward, he sends a Grunt spy to Alpha Base; the spy reports that the Chief has gone there sometime before the events of the level "343 Guilty Spark". This is impossible, as from the Silent Cartographer, the Chief goes straight to the area around the Control Room, and then straight to the swamps in the level. However, the book does say that Foehammer picked up the Chief to bring him back to Alpha Base, where he "scarfed a quick meal and a couple hours of sleep", so it is possible that Yayap saw him at that time.
 * Sergeant Stacker is not mentioned in the novel. He is replaced during the raid on the Truth and Reconciliation by Sergeant Parker, and for the raid on the Silent Cartographer by Gunnery Sergeant Waller. One place where he might make an appearance is when the Chief rescued a crashed Marine squad with a Sergeant and where Stacker is normally found in the game.
 * At one point, the book states: "Consistent with his status as a veteran, the first alien to come around the corner wore red-trimmed armor, a methane rig, and a Marine's web pistol belt. The alien wore the captured gear Pancho Villa-style and dragged it across the deck. Two of his comrades brought up the rear." That is three Grunts in the Master Chief's sight. The next paragraph says, "Confident that there were more of the vaguely simian aliens on the way, the Master Chief paused long enough to let more of them appear, then opened fire. The recoil compensators in his armor dampened the effect, but he could still feel the handgun kick against his palm. All three of the Grunts went down from head shots." It is as if the extra Grunts that appeared simply disappeared. Only three Grunts were killed yet, which are the three original Grunts that first appeared, the leader and the two followers. But "...the Master Chief paused long enough to let more of them appear, then opened fire... All three of the Grunts went down from head shots." It is possible, though, that the Master Chief had simply expected more Grunts to appear; he may have simply waited in case more Grunts appeared, and then opened fire when he was sure there weren't any. It is also possible that Master Chief was simply waiting for more of the three Grunts to appear, giving him larger target silhouettes to hit.

Halo 2

 * In the video "Another Day at the Beach", soldiers depicted are the ODSTs. During gameplay, the soldiers at the hotel are just standard Marines. Also, the location of the crashed Pelican does not match its position in game.
 * This can be because the cutscene was cut from the original game.
 * In the level Delta Halo, you can find dead ODSTs all around the level -- 7 to be exact. However, In Amber Clad only dropped 11 HEVs... 3 ODSTs, the Master Chief, 3 more dead, and the seven ODSTs makes 14 dead soldiers. This may just be a secret 7 reference, however, as 7=7 and 7x2=14. It is also possible that In Amber Clad launched more HEVs.

Halo: First Strike

 * The Longsword that landed in the Ascendant Justice is repeatedly referred to as a Pelican.
 * Vinh is referred to as Spartan-029, even though that was Joshua's tag. The mistake is probably a typo.
 * It is stated that Dr. Halsey always referred to John by name, and never by rank or serial number. But in Halo: The Fall of Reach, she called him "Master Chief" repeatedly.

Halo 3

 * Every Longsword fighter bears the marking 7-89 on its side, despite that each Longsword has a different ID number. This is likely the result of reusing the same model.
 * In the ending cutscene of the level The Storm, all of the UNSC Frigates have the same serial code, and all are labeled "Forward Unto Dawn". One of the Frigates is actually the Forward Unto Dawn. This is also likely the result of reusing the same model.
 * The portal to the Ark is an actual physical object on Earth, but above the Ark, the Fleet of Retribution appears as if it were coming out a Slipspace jump. When the Arbiter and the Master Chief were going back to Earth, the tip of Forward Unto Dawn went through a physical portal, even though there wasn't one in the cutscene before The Ark.
 * The huge glow of the portal on Earth could be a result of the Slipspace rift energizing atmosphere. The portal would therefore be invisible in outer space. When Instilation 05(b) was falling apart it was likely leaking atmosphere rendering the portal visible.
 * It is possible that the ortal on Earth simply sent them to the Ark and a return portal was ignited off screen in the viscinity of the Ark. in other words the portals wern't linked to each other

Halo Wars

 * In the level Dome of Light, after requesting the first Rhino to be deployed, the radio operator on the Spirit of Fire will identify you as "Harvest Surface Command" even though the level takes place on Arcadia, however this could be that the Spirit of Fire was still assigned to Harvest.
 * The Spartans must be wearing Mark IV armor because the story takes place in 2531, 24 years before Reach would fall to the Covenant. However, the Spartans in the game possess recharging energy shields, a feature that would only be added in the Mark V armor. This is only a gameplay mechanic and should not be taken as canon.
 * The Spirit of Fire is presumably equipped with a standard UNSC MAC. A destroyer-class vessel can fire 2 rounds with one charge, as it possesses 2 separate MACs. The Pillar of Autumn could shoot 3 rounds with one charge, as it possessed an advanced prototype. Super MACs around Reach and Earth could fire one round every 5 seconds. But somehow, the MAC aboard the Spirit of Fire is able to deliver 4 rounds with a single charge, something that is unheard of in a shipborne MAC. However, as the rounds do very little damage to the area surrounding their targets, it may be assumed that the rounds, or the MAC itself, are not standard, or that the rounds are fired with a lower-than-normal charge.
 * Only Honor Guards are permitted to wield energy staves. However, in the cutscene "Monsters", in which the Spartans are fighting with the Elites when Sergeant Forge is trying to activate the reactor, blue-armored Elites are equipped with energy staffs. This may mean that these were Honor Guards composed of Elite Minors, or Elite Minors were given energy staffs to fight with.
 * In previous cutscenes with the Prophet of Regret, the Elites that are guarding him are clad in red armor, as Elite Majors are. Later, the Honor Guards are shown fighting the Spartans in blue armor. An explanation might be that the Arbiter ordered the red-armored Honor Guards to accompany the Prophet of Regret back to High Charity.
 * In the cutscene where Professor Anders is captured, Red Team pulls up in a Warthog armed with a quad-barreled Gatling gun. Throughout the entire Halo series, the M41 LAAG has only 3 barrels. This is either a new variant of the M41 LAAG or simply an error on the part of the developers. This four-barreled design is featured on all renders of the weapon that have been produced for Halo Wars, including those created for franchising purposes.
 * The Mk IV armor worn by Red Team and Team Omega differs in many aspects with the armor in Halo: The Cole Protocol. Though Gray Team's armor may simply be highly customized, the differences are present in everything from the waist up, showing either a complete upgrade of the Mk IV, or different artistic intentions were involved.

Manual vs Books
(These discrepancies are created when material from the game manuals is inconsistent with material from the novels.)


 * The Halo: Combat Evolved Manual states that the Harvest incident took place in 2520, while all other sources specify 2525.
 * The manual also states that Captain Keyes has served in the UNSC since 2526, though he was fresh out of the UNSC OCS in 2517.
 * The Grunts are referred to as being five feet tall, but in The Fall of Reach, they are referred to as being a meter tall (a little over three feet).
 * In Halo: The Flood, the Chief spots some 12-gauge shotgun shells near an entrance. In the manual and in all other media, they are said to be 8-gauge.

Game vs Books
(These are created when the novels describe events that are not the same as what is seen in gameplay. As explained in this forum post, the games are considered by Bungie to be more canon.)


 * Jackals and Special Ops Elites are on board the Pillar of Autumn. This does not occur during gameplay on any difficulty.
 * The primary insertion group during the Truth and Reconciliation assault is made up of ODSTs, while in-game there are only Marines. ODST's did appear in Halo: Combat Evolved (contrary to popular belief), although they did not wear ODST Body Suits in that game. These could have been separate insertions, but a singular attack is more likely.
 * Cortana identifies Halo in Halo: The Flood when escaping the Pillar of Autumn, but it isn't identified until the level Truth and Reconciliation in the game.
 * Halo: The Flood describes only four Scorpion tanks being retrieved from the Pillar of Autumn, which does not account for the one in Assault on the Control Room. Fire Team Zulu was working out of Alpha Base, so they could have been ordered to bring the tank, which would account for it being near a downed dropship.
 * Cortana accesses Halo's Control Center by having the Master Chief remove the memory chip from his helmet and place it in the console, while in the novel she broadcasts herself into the system using the suit's transmitter.
 * UNSC ships use rotating sections to simulate gravity yet no such mechanism is seen in-game. This could be accounted for if the rotating parts were inside the ship. The Pillar of Autumn may also have been using the reverse-engineered Covenant technology called Gravity Plating instead of rotating sections.
 * The Pillar of Autumn's MAC cannon is depolarized and cannot fire, yet the gun is apparently used, and the loss of fire control still makes headlines (Halo:CE, opening cinematic).
 * The cutscene in Halo:CE at the end of the level "The Pillar of Autumn" clearly shows the Autumn being fired upon with plasma. However, in the novel, the Prophet at the ring forbids the Covenant ships to fire, lest they strike the "sacred relic". However, the order could have been ignored or overruled (perhaps by the Supreme Commander to stop the Autumn from hitting the surface, as the Prophet's demand was made before the ship was even boarded.)
 * Grunts love to overcharge their plasma pistols in the books, yet they never do so in the games.
 * In the game, Master Chief throws Pvt. Jenkins' Record View away, but he still has it in First Strike. This could be explained by the Chief's suit automatically making a copy of Jenkins' recording as a possible means of gathering intelligence, like today’s armed forces gathering dog tags from the dead, although this is only a theory.
 * On several occasions in the books (too numerous to list), UNSC forces are mentioned as switching their MA5Bs from bursts to full auto, although in the games, they are only capable of fully automatic fire. Likewise, in First Strike, Vinh fires two single shots at an Elite with her BR55.
 * In the Halo Graphic Novel -- specifically the Last Voyage of the Infinite Succor -- the Flood are shown consuming every possible living creature they can find, yet in the games, it seems that they are only interested in intelligent beings. Additionally, the Halo Array was mentioned as only being able to kill beings with sufficient biomass and intelligence to support the Flood. However, the Flood was in its feral stage, and could have been searching for more calcium to sustain its Proto-Gravemind.
 * In the game Halo 3, under the Multiplayer Armor Permutations menu, it states that the ODST helmets were used for the Spartans to train in. However, this is never mentioned in Halo: The Fall of Reach. It may have been omitted, however, as large sections of the training are missing from the book.
 * In Halo: The Flood, most of the Marines described in the book were female, despite no female marines being in Halo: Combat Evolved at all.
 * In Halo 2, Cortana says that the Covenant didn't expect humanity to be on Earth, but in Halo: First Strike, immediately prior to the Battle of Earth, the Covenant clearly knew that humanity was on Earth, and had a gigantic fleet to deal with it.
 * In Halo: The Flood it describes the hunters spikes as being retractable.

Books vs Books
(These errors happen when information from some of the novels is inconsistent with information from other novels.)


 * 33 SPARTAN-IIs successfully adapted to the augmentations, but there have been too many listed. Kurt-051, Sheila, and Randall were listed as MIA before 2552, as were Jai-006, Adriana-111, and Mike. Samuel-034 and three other Spartans were KIA, and one WIA , but thirty SPARTAN-IIs were present to defend Reach (John-117, Linda-058, James, and twenty-seven of Red Team), when there should have been only twenty-two (or possibly only nineteen, as it is unknown whether Jerome-092, Alice-130, and Douglas-042 returned to UNSC-controlled space).
 * it is possible some of the "washouts" that survived recovered from their side affects
 * Pelican's operational maximum is listed as 12 Marines, elsewhere as 3 crew, 10 seated, 5 standing , yet still elsewhere they can carry 75 children , 30 Elites , or 27 Spartans . It should be noted, though, that the Pelican in Halo: First Strike has all the unnecessary equipment removed -- likely including the seats -- and the Spartans are more or less jam-packed into the small craft.
 * It is possible, that there may be different variations of Pelicans though we only see the one type in game, or that these were equipped with some kind of troop bay extension.
 * During the Battle of Reach, many Covenant ships are destroyed, but not before they can loose their own lethal plasma attacks. However, later plasma en route to a target merely dissipates as the originating ship and its magnetic controls are destroyed. It is possible that the magnetic controls were not destroyed in the former instance, allowing the plasma to continue to its target.
 * Halo: The Fall of Reach states that Harvest has a population of 3 million. However, in Halo: Contact Harvest, it is stated to have a little over 300,000.
 * Lieutenants Hall and Dominique are introduced as members of the command crew of the Pillar of Autumn, but are absent when the ship arrives at Installation 04. It should be noted, though, that Halo: The Fall of Reach states that there was a flutter in Dominique's heart when he came out of cryosleep prior to the discovery of Alpha Halo, perhaps indicating cardiac arrest.
 * Engineers are supposedly first seen by humans during the Battle Of Sigma Octanus IV in 2552. However, in Halo: Ghosts Of Onyx, when Kurt is reviewing a mission of the SPARTAN-IIIs some years prior to that battle, he saw Engineers. Such information could have been kept classified by the ONI due to the secrecy of the SPARTAN III program. Engineers are also occasionally seen in the campaign of Halo Wars, which takes place in 2531.
 * Chronologically, the first time Brutes are encountered by the UNSC was at the Battle of Harvest in 2525, yet the Master Chief has no intelligence on them until the attack on the Unyielding Hierophant in 2552. This could be accounted for by the secrecy of the first encounter with the Covenant, as ONI could have tried to cover up the failure of the negotiations with the Brutes. Like the Huragok, Brutes are also seen during the events of Halo Wars.
 * In 2525, when Harvest was glassed by the Covenant, UNSC technology took approximately two months to traverse between Harvest and Reach, but in 2552 it takes a ship only 19 days to travel between Reach and Earth, when the distances between the three planets are only between 10 and 11 light years.
 * Human Slipspace travel times are inconsistent because of limited technology
 * Throughout Halo: Ghosts of Onyx, Elites referred to superiors as "sir", while in Halo: The Flood, they said "Excellency". It is possible, though, that the two words are English translations of the same Sangheili phrase.
 * In Halo: First Strike, Dr. Halsey puts 4 sub-machine guns and 16 clips of ammunition in a bag. In Halo: Ghosts of Onyx, Kelly found the same weapons, but they were 4 MA5B Assault Rifles instead.
 * The BR55 (Battle Rifle) is said to be a prototype weapon on the planet Harvest for Captain Ponder's militia in Halo: Contact Harvest. However, in Halo: First Strike, some thirty years later, the SPARTAN IIs only just get the weapons, despite being the top choice to receive the weapons.
 * Jai remembers being abducted and brought to Reach along with seventy-five other children. In fact, there would have only been seventy-four other children.
 * it is possible he is rounding up
 * Prior to 2525, UNSC ships used rotating sections to simulate gravity, and the Spartan-II's were surprised to discover artificial gravity on the Covenant ship they boarded. However, since then, multiple human facilities and ships are shown to have artificial gravity capability. It is possible that this technology was adapted from the Covenant, but that is unlikely due to the difficulty in capturing intact Covenant ships, much less reverse-engineering them. The most likely possibility is that the writers use anti-gravity technology for convenience purposes. It is also possible, though, that the rotating sections exist between the walls and outer hulls of UNSC vessels.
 * When Lieutenant Keyes is warned of the incoming Covenant fleet and asks what UNSC ships are nearby in Halo: The Cole Protocol, the book first states that three Destroyers are picketing, but immediately counters that the and three frigates wouldn't be able to repel a Covenant assault. However, they are later confirmed to be Destroyers, one of which is the Do You Feel Lucky?.
 * Chief Petty Officer Mendez remarks that some of the Alpha Company candidates were orphaned at Jericho VII. His speech takes place on December 12, 2531, yet Jericho VII was not glassed until the February of 2535.
 * In Halo Wars: Genesis, Ellen Anders mentions the planet Onyx in passing, while giving a talk about an alien presence. However, in Ghosts of Onyx, Kurt reads a file that says Onyx has been classified since 2511. Genesis takes place in around 2531.
 * In Halo: The Flood, it is stated that lowering your eyes is a sign of respect. However, in The Cole Protocol, it was said that refusing to meet one's eyes or lowering their head was a sign of their shame.
 * In Halo: The Flood it says Captain Keyes killed his first human with a pistol however the Cole Protocol states it was a plasma rifle.

Game vs Game
(This occurs when information from one game is not consistent with information from another.)
 * In Halo: Combat Evolved, the Master Chief needs to insert a chip into the back of his helmet to house Cortana in his Mark V Mjolnir armour. In Halo 2, with the upgrade to Mark VI, all he needs to do is touch something to allow her to move from his suit to another power source. It is reverted back to the chip in Halo 3, however, it gains some of the properties of the touch ability in Halo 2. Why technology went backwards in between Halo 2 and 3 is unknown. Although this could be because the suit might interface differently with a bomb as opposed to Halo's control center, or because Master Chief's armor suit was damaged in the fall from the Forerunner Dreadnought to Earth.


 * In Halo: CE, the Sniper Rifle had night vision, but it is absent from Halo 2 and Halo 3. This is likely due to its limited purposes, but it is still strange to see a weapon losing an advantage, and the different versions of the Sniper Rifles during the era could not be accounted for that loss.


 * The doors in High Charity are different in Halo 2 and Halo 3. This could be because the High Charity part of Halo 2 takes place near the Prophets' Sanctum, and in Halo 3, near the core area so there is a difference in design.