These doors can be encountered in every mission and you will have to open a lot of them. There are both silent and loud ways to open them.
You can open this door silently with a lockpick. It can also be opened with a crowbar or a drill, but these will force the door open which will get detected by NPCs. If you have the Precision Drilling perk the door will not be forced open, but NPCs will detect it if they open it or see it open. For loud you can shoot the lock of the door with any weapon to open it instantly and any explosive will open it too. In the SCRS there is a gray variant of this door. In the Scientist most wooden doors have glass windows.
Metal Doors are first encountered in The Deposit. They usually indicate a higher level of security and are more difficult to open than wooden doors. The door comes in two colors, light grey in most missions and dark grey in The Blacksite.
You can open this door silently with a lockpick. It can also be opened with a drill or a blowtorch, but these will force the doors open. The blowtorch can also be used to burn a small hole into the door, which can be used as a hole to shoot at enemies. In The Blacksite, some metal doors can also be opened by a crowbar. This door can also be opened with any explosive. You cannot shoot the door handle to forcefully open the door as it is metal.
Keycard doors are first encountered in The Freelancer. They are almost identical to the metal door with the only change being that they can not be opened with a lockpick. They can be drilled, blowtorched, and blown open like the Metal Door.
To open it silently you have to use the keycard scanner which is located next to the door. The scanner can be hacked with a keycard scrambler or opened with a keycard. Once you close the door it will lock again, so you will have to use or hack the scanner again. If the door does not have a scanner on both sides, it can be opened from the inside by interacting with it like unlocked doors. The door can also be opened by any explosive.
The glass doors can be encountered in The Deposit, Withdrawal, the Cache, and The Auction. These doors serve as the entrance to the banks. They can also be seen on The Freelancer as part of the environment with an alternative texture. Most have a white color paired with a sand texture and they will break if shot with a weapon.
These doors can only be encountered in certain missions and are usually unique.
Heavy Security door
This door can be seen in The Financier and The Lakehouse. This door can be opened by blowtorching its right side, drilling 2 places on its left side, blowing it up with C4s/Thumper shots (2 in The Financier, 3 in The Lakehouse), using a keycard scrambler to activate the timelock in The Financier, or using a code to open it in The Lakehouse.
The door can be quickly opened up from the Inside on both Financier and Lakehouse. In The Financier it will stay permanently open after that while in Lakehouse it can be closed again if the Alarm has yet to sound.
The one in The Deposit is a regular metal door that has sensors at the top. The camera operators will raise the alarm if you open the door while the sensors are active. The lower door at the back alley will always have a sensors, and door of the upper camera operator will have a sensors on Elite or above. The sensors can be disabled by an engineer and they will not trigger the alarm if both camera operators have been taken out.
The one in The Withdrawal is a fire exit which can only be opened after an engineer disables the sensors next to it. This is used as a much faster and safer way to get money to the van.
These doors with magnetic locks can be found in The Lakehouse. They can only be opened with a blowtorch or by rewiring the outer power box. However, rewiring the box only opens one of the doors. They can also be opened with explosives.
Shadow War Door
This door is only found in the PvP gamemode Shadow War. The ones on the outer edges of the map can be opened by a crowbar, the others can be opened by interacting with them. A blowtorch also allows you to burn a small hole into the doors. They make distinct noises when opened or closed.
High-security keycard doors are first encountered in The Scientist. They require a high-security keycard to open and have a short timelock to them. The ones found in The SCRS can also be opened with explosives, drills or blowtorches.
There is a special variant of this door in The Cache which can only be opened by completing a mission objective.
Chip Reader door
This door can be found in The SCRS and Black Dusk. It is similar to a keycard door, except there is a chip reader on the side instead. Unlocking a chip door requires a specific disguise, which is specified by the chip. This can also be permanently bypassed through a lengthy process with an engineer. Like keycard doors, the chip door will lock when closed, unless it has been permanently disabled by an engineer. Any NPC that sees a chip door left open will be lured over and close it.
The blast door can be found in The Blacksite and Black Dusk. It can be opened by interacting with a panel next to it, however this is only on Silent, and on Loud you must defend the panel for a long amount of time on Blacksite. In Black Dusk, you need to unlock blast doors via the control room on Loud, where you then will have to defend the panel to be able to open it.
These doors are usually only found in a certain mission and do not act like regular doors.
Vault Cell Door
This door can be found in the vault of The Withdrawal and The Freelancer. It is made up of gray metal bars and can be opened with a lockpick, drill, blowtorch or any explosive. There are also two cell doors in The Blacksite that will automatically open after meeting Rose.
Jail Cell Door
The Jail Cell Door is a gray door that can only be found in the prison block of The Blacksite. It can only be opened by interacting with the panels found in the security room. On Professional+, you need to use a drill or blowtorch to make a small hole to find Rose without having to open every door.
Server Room Door
This door can be encountered in the basement of The Lakehouse. It can be opened with the Head of Security's keycard. Scanning the keycard on the timelock begins a timelock where the amount of time it takes depends on the difficulty. It has two other unique features compared to the metal door. It cannot be opened with a Breaching Charge, however, it can be opened by using C4 or by shooting the breaker box in the server room (usually with a 480 MCS or CH-A with Sniper Mastery, although other guns can be used).