Under night in-birth is new to steam, but it’s been out for over a year on playstation 3 and even longer than that in arcades, so many players are already really strong. While that means it might be hard to win online, it also means there’s a lot already known about how to play the game. This guide will explore universal system mechanics and introduce higher-level concepts important for competitive play.

The under night community largely uses numpad notation for in-game actions. In numpad notation directions are represented by numbers corresponding to their location on a keyboard numpad, thus 2=down, 6=forward, 4=back, 8=up, and 5=neutral. You can combine the numbers to make joystick motions, IE the motion for hyde’s orbiter special move would be written as 236A for down, down-forward, forward and then the A button. Throughout this guide I’ll be using numpad notation, but I’ll also provide a description of each action as well for players not used to it.

Run vs Dash
Inputting 66(double tapping forward) or 6A+B (hold forward, hit A and B at the same time) will cause most characters to start a run. Runs last for as long as you hold down forward and can be canceled at any time by any action, including blocking. This makes them very useful for closing distance since you retain all of your options.
Akatsuki, Vatista, and Waldstein don’t have runs, instead they get a short dash which moves a fixed distance. Dashes are slower than runs, but they can still be canceled into anything. While the slower speed of dashes generally makes them worse, they have 1 big advantage over steps. Since the distance they move is fixed you can input a dash, then hold back or down-back to move forward while blocking.

Backdash
Inputting 44(double tapping back) or 4A+B (hold back, hit A and B at the same time)will cause your character to quickly move backwards. Backdashes all have invincibility on start-up, although how long that lasts varies from character to character, so they’re not always dependable reversals.

Assault
Inputting 6D (hold forward, hit D) will cause your character to quickly hop up into the air. The horizontal distance that an assault travels depends on how far away you are from your opponent, but their total duration is always the same. Once you’ve assaulted you do any 1 normal air action, but you cannot airblock. This makes them good for pressuring an opponent, trying to open someone up with fairly quick overheads, or for escaping your opponents throws
Performing an assault in the air or hitting 66(double tapping forward) while airborne will let you assault from mid-air. An air assault always travels the same distance, and lets you do as many air actions as you want afterwards (although you only get 1 assault per jump and still cannot airblock). Air assaults are mostly useful for changing air momentum or delaying your landing.

Blocking
Holding back will cause your character to block. Some attacks are overheads and must be blocked while standing, some are lows and must be blocked while crouching, some are mids and can be blocked in any direction.

Shielding
Hitting the D button while holding back will cause your character to shield block. While shielding you cannot change your block state, but will experience less blockstun and will push the opponent back. Shielding is also one of the main ways to build GRD. Shielding is similar to instant block mechanics in games like blazblue and guilty gear. If you shield a jump attack, the opponent will lose all their cancel options and they’ll get extra landing recovery, making them much easier to punish.

Green Shield/Guard Shield
If you press the D button while in blockstun, your character will flash green and be considered shielding. While green shielding you are allowed to change your block state, but it will take 10 points of meter.

Air blocking
While in the air, holding back will cause your character to air block. Many moves are air unblockable in under night, most ground normals and ground specials are, and all air normals are only air blockable through air shield.

Guard thrust
Guard thrust is an attack done by inputting 214D(Down, Down-back, back +D) while in blockstun. Because it removes you from blockstun guard thrusts can be very useful for escaping pressure, however doing so takes all of your super meter (you must have aleast 100 to attempt a guard thrust) and will put you in a GRD break state (for more on GRD break check the misc mechanics section)

Throws
Throws are done by inputting A+D. They cannot be blocked, but can be teched by hitting A+D right as you’re getting thrown. If you attempt to throw an opponent who is in blockstun or hitstun, they’ll flash yellow and will have a much longer tech window. When coming out of blockstun or hitstun, characters have a brief period of grab invincibility. Normal grabs cannot hit an opponent who is airborne, but some command grabs can. Additionally, Akatsuki and Eltnum both have air grabs, done by inputting A+D while airborne, these will grab airborne opponents, but whiff against grounded opponents.

Meter
There are 2 universal meters in under night, one is a super meter called either EXS or FLS depending on your character (both EXS and FLS function the same) which works like a standard fighting game super meter. And the other one is called the Grind Grid which is unique to under night.

EXS and FLS
Characters can stock up to 200 points of super meter. Ex moves require 100 points of meter, and Super moves (called infinite worth) require 200 points.

Concentrate
By holding down the D button a character can concentrate, which builds GRD at a rapid pace, but also drains super meter.

Grind Grid
The Grind Grid (or GRD gauge) is very unique to under night, both players gain and lose chunks of it (called GRD) by doing various actions including moving forward, assaulting, successfully shielding, hitting an opponent, whiffing a throw, using their force function, and many more. A ring in the center of the gauge slowly fills up (about once every 11 seconds) and when it does whichever player has more GRD starts glowing and enters a state called “Vorpal”. If the players are ever both will enter vorpal.

Vorpal
While in vorpal, characters do more damage, can guard thrust for no meter and have the option to perform a “chain shift” by double tapping the D button.

Chain shift
A chain shift is similar to a roman cancel from guilty gear, it can cancel most moves, will freeze the game for a split second, and returns you to neutral. Performing a chain shift will drain all your GRD, end vorpal, and give you super meter relative to how much GRD you had. Chain shifts are useful for extending pressure, extending combos, and just for meter gain.

Veil off
By inputting A+B+C with at least 100 meter, any character can perform an invincible explosion. After the explosion their super meter will be replaced by a veil off timer that slowly drains. As long as this timer exists, the character is considered to have infinite meter, although doing any ex moves drains chunks of the Veil off timer and doing an infinite worth drains it completely

Infinite worth & infinite worth EXS
Infinite worths are universally done by inputting 41236D (back, down-back, down, down-forward, forward, D), but their properties vary from character to character. Most character’s Infinite worths are invincible (only byakuya’s and hilda’s aren’t). Infinite worth EXS is done by pressing A+B+C+D and is universally a giant pillar with little horizontal range, but huge vertical range. Infinite worth EXS is universally hit invincible, but vulnerable to grabs.

GRD break
When hit out of a shield, hit by a veil off, or after performing a guard thrust or Infinite worth EXS outside of vorpal, characters will enter GRD break. GRD break is visually shown by half of the Grind Grid cracking, a timer will also show up near the broken half of the grind grid and count down how long the GRD break will last. While GRD broken any action normally done with the D button cannot be performed with the exception of infinite worth moves. This includes assaulting and shielding, so it can be very dangerous. Performing a veil off will remove GRD break status.

Force function
Pressing B+C will perform a force function. Each character has a unique force function and has different uses for them, but all force functions cost 1 block of GRD. If you don’t have any GRD you can still use your force function, but it will instead give GRD to your opponent.

Increase
Some moves can be held for extra properties. This is called increase and once a move has been charged, the character will flash white. Increase is usually abbreviated as “IC”

Passing link
All normals can be chained into each other once and only once (with the universal exception of 2a, which can chain into itself an unlimited number of times). This is the same chain system as “reverse beat” that Crescent and Half moon characters have in melty blood.

Smart Steer
By pressing 5A(standing A) repeatedly the game will do a preset combo for you. This is very similar to persona 4 arena's auto combo, although instead of having completely unique normals like persona, smart steer uses a characters pre-existing normals. An important aspect of smart steer is that smart steered attacks will always come out, even if the rules of passing link say they shouldn't. This means a character like Gordeau can do 2A>5B>5A>5A (crouching A>standing B>standing A>standing A) to use 5B(standing B) twice in a single chain.

Chaining into whiffed normals
Most normals have a lot of recovery, so much so that it’s usually faster to chain into a quick shorter range move and have it whiff than it is to just let the slower move recover. This means that it’s usually best to save an A normal in your passing link string for the end as you can make unsafe normals safe.

Taking advantage of a knock down
When an opponent is knocked down, you typically have a lot of time to both move close to them, and to start pressure. Because you have so much time, moves that are otherwise too slow to use on a defending opponent can be started while they’re still knocked down and then hit them as soon as they wake-up. This is called a “meaty attack” and is part of the larger concept of pressure done on a knocked down opponent, or “okizeme” (often abbreviated as “oki”). Carmine and Byakuya are examples of characters who have strong Okizeme, since they can force you to block blood wheels or webs as you wake up, however every character has some form of okizeme.

Dealing with reversals on wake-up
Reversals (also known as DPs or “Dragon punches”) are moves that have invincibility on startup, it’s common for people to do them when getting up from a knocked down state since that’s a simple way to beat a meaty attack. Invincible moves are usually punishable on block, so waiting and blocking is the simple, universal way to beat them. But, it’s possible to do both a meaty and block a reversal with a technique called a “safe jump”. Since jump attacks are canceled on landing, doing one very close to the ground right as the opponent gets up can let you hit them if they do nothing, or land during the startup of their reversal and block it if they DP. This requires a fairly long knockdown, so it’s not always possible, and timing for a safe jump them can be tight. An example that’s not too hard to do is ending an akatsuki corner combo with neutral jump C>j.2C(neutral jump C, then jumping down C), then assaulting and doing jumping B close to the ground as the opponent wakes up. You can see a demonstration in this video:
If you want to try it yourself I suggest using an easier starter, like 6C(forward C) to launch the opponent up rather than trying to use parry.

Dealing with assault/throw
Teching grabs can be hard, since if the opponent doesn’t grab you and tried to tech you’ll end up whiffing a grab. But if you input A+D while crouching you won't whiff a grab, instead you’ll either get crouching shield or 2A(crouching A) depending on if you’re blocking or not and if you get thrown you’ll still tech it. While randomly crouch shielding is really risky, it can be better than whiffing throw, and 2A(crouching A) isn’t particularly risky.
You can then take things a step further and input 3A+D+ B or C(down-forward A+D+ B or C) to get some kind of anti-air. 3B/3C(down-forward B/down-forward C) is a common input for anti-air normals (Carmine’s 3b(down-forward b), and Hyde’s 3C(down-forward C) are both good examples) so you end up either teching a throw or hitting an opponent out of an assault. This is nice since throw/assault is a universal mix-up that can be otherwise hard to defend against.
This technique is an option select generally called a “crouch tech” or a “grap”

Dealing with empty jump low
Usually when defending against an opponent that’s jumping at you you try and stand block since jump attacks are typically overheads and are generally too fast to react to. Because of that, an opponent who jumps at you, presses nothing in the air, then lands and does a low hitting attack can be hard to block. This can be especially hard to block when dealing with a character like carmine, who can start to do his jumping C attack, then charge it long enough that the move never even comes out, and then do a low. To make blocking these easier, rather than trying to react to an opponent doing a move in the air or landing, simply hold back, then the moment when the jump attack would hit (regardless of weather it did or not) you switch to blocking low. This sounds complicated but is very simple to execute in practice. This technique is an option select sometimes called “fuzzy guard” but be aware that there are many other different techniques also called fuzzy guard. It is also sometimes referred to as “OS blocking.”

Understanding frame data
You might hear terms like “frame advantage” “active frames” or see things like “-3” and be confused, but don’t worry, despite seeming very mathy, frame data is very easy to understand. First you need to know what a frame is. Under night in-birth runs at 60 frames per second (or should at least), so “frame” is used as a measurement of time which is equal to one sixtieth of a second. Moves are broken down into 3 parts: Startup, active, and recovery. Startup frames are frames before the attack can hit, active frames are frames where the attack can hit, and recovery frames are frames after the attack has hit. Startup also encompases the first active frame. Frame advantage is the concept of being able to act before your opponent, so if a move is +5, that means you have 5 frames to do something before your opponent can do anything. Alternatively, if a move is -5 that means your opponent can do something 5 frames before you can do anything.
So if you’re at -5, and your opponent has a move that’s 5 frames or faster, they can hit you and you cannot block.

Basic system guide
A shorter look at the game's system mechanics

Dustloop under night subforum[www.dustloop.com]
Forum for discussion, there's lots of character specific tech in the various character threads as well

In-birth wikia[in-birth.wikia.com]
Wiki with lots of story info if you're into that, but also lots of detailed info for each character

Under night mizuumi wiki[wiki.mizuumi.net]
Wiki exclusively devoted to competitive play

Under night beginner character guides
If you like this guide check out my series of video guides for characters, There aren't many but there are some!

7/13 - Added a section on smart steer to misc cause I realized I forgot it originally
7/15 - Reworded the intro
7/16 - Added a link to character guides