Facial Action Coding System (FACS) Cheat Sheet+

A visual reference guide for the Facial Action Coding System (FACS) and beyond, featuring action units (AUs) and their corresponding musculature. Designed for animators, modelers, riggers, sculptors, and researchers.

The former “cheat sheet” is available here: “FACS Study Guide.

IMPORTANT NOTE

#notFACS indicates actions I have identified and coined that do not exist in FACS. Due to FACS’s original purpose as a facial behavior identification system, FACS lacks documentation for some finer, more nuanced facial movements. To fill this void, I have further defined my own nonFACS movements such as: vertical lip tightener, y-axis dimpler, open-eye blink, etc. If you work on lipsync technology or photoreal characters, these distinctions will be particularly useful.

FOREHEAD AREA & EARS

FACS name

muscle name

expression reference

AU1 – inner brow raiser

frontalis (the medial portion)

AU1 ACTION: Inner brow raiser lifts the medial brow and forehead area.

NOTE 1: Inner brow raiser is variable in wrinkle formation and range. This variability is due to a number of factors, a prominent factor being frontalis muscle variability. 

NOTE 2: Further reading on inner brow raiser – 1) Inner Brow Raiser Deep Dive, 2) The Secret Life of Inner Brow Raiser.

AU2 – outer brow raiser

frontalis (the lateral portion)

AU2 ACTION: Outer brow raiser lifts the lateral brow and forehead areas.

NOTE: As mentioned with inner brow raiser, outer brow raiser is also variable in wrinkle formation and range. This variability is due to a number of factors, a prominent factor being frontalis muscle variability.

AU4 – brow lowerer

corrugator supercilii, depressor supercilii, and/or procerus

AU4 ACTION: Brow lowerer knits (corrugator supercilii) and lowers (procerus, depressor supercilii, and parts of corrugator supercilii) the brow area and lower central forehead. **Read NOTE below for important considerations.

NOTE: Brow lowerer can be performed by any or all of the above listed muscles. Though FACS lumps together the actions of all three of these muscles, when I teach facial anatomy and FACS, I separate out the movements. See more in the FACS Study Guide.

ears up & back

#notFACS

auricular muscles (see notes below)

EARS UP & BACK ACTION: Ears up & back lifts the ears and pushes them back.

NOTE1: This is not a FACS action. I have included this ear movement in the FACS Cheat Sheet, because I observe it happening relatively frequently.

NOTE 2: There are multiple auricular muscles. The superior auricular moves the ears up. The posterior auricular moves the ears back. The anterior auricular the moves ears forward. At present, I cannot separate these movements. The reference here shows posterior auricular + superior auricular movement.

EYE & CHEEK AREA

FACS name

muscle name

expression reference

AU5 – upper lid raiser

levator palpebrae superioris

AU5 ACTION: Upper lid raiser pulls the top eyelid up and back to widen the eyes.

NOTE: For more on upper lid raiser: (1A) – If you are a subscriber, view All About Upper Lid Raiser – or – (1B) View Stylized Facial Expression Design. (2) If you are not a subscriber, you can view the preview post of All About Upper Lid Raiser here.

AU6 – cheek raiser

orbicularis oculi (the orbital portion)

AU6 ACTION: Cheek raiser tightens the outer rings of the eye orbit and squeezes the lateral eye corners.

NOTE: For help differentiating cheek raiser from lid tightener, see Cheek Raiser vs. Lid Tightener.

AU7 – lid tightener

orbicularis oculi (the pre-septal portion of the palpebral area)

AU7 ACTION: Lid tightener tightens the rings around the eyelids and pushes the lower eyelid skin toward the inner eye corners.

NOTE: For help differentiating cheek raiser from lid tightener, see Cheek Raiser vs. Lid Tightener.

open-eyed blink

#notFACS

orbicularis oculi (the pretarsal portion of the palpebral area)

OPEN-EYED BLINK ACTION: Open-eyed blink tightens the innermost rings around the eyelids in a circular motion toward the inner eye corners.

NOTE: The pretarsal area is the portion of our orbicularis oculi muscle that is involved with blinking. See more breakdowns here.

AU45 – blink

orbicularis oculi (the pretarsal portion of the palpebral area)**

AU45 ACTION: Blink closes and opens the eyes in a swift, fluid manner.

NOTE: Beyond pretarsal activation, blink also often consists of: (1) relaxation of levator palpebrae superioris and/or (2) forced closure from the preseptal portion of orbicularis oculi.

AU46 – wink

orbicularis oculi

AU46 ACTION: Wink closes one eye, usually with some compression.

NOTE: Unless you are a facial coder conducting behavioral research (and even then, the official FACS Manual lists AU46 – wink as “optional”), the FACS shape for wink is not the most useful. I have included it because other FACS lists include it; however, I find it to be a clunky, unnecessary addition to most shape sets. That being said, orbicularis oculi does deserve better functional breakdowns beyond cheek raiser, blink, and lid tightener – but wink is not the way to go. In the near future, I will post a functional breakdown of orbicularis oculi. Sign up for monthly post updates to keep tabs on the latest content and breakdowns.

MIDDLE FACE & NASOLABIAL AREA

FACS name

muscle name

expression reference

AU9 – nose wrinkler

levator labii superioris alaeque nasi (+ usually depressor supercilii and/or procerus)

AU9 ACTION: Nose wrinkler lifts the sides of the nose, nostrils, and central upper lip area. 

NOTE: The brow lowering you see in nose wrinkler is not directly caused by the levator labii superioris alaeque nasi (LLSAN) muscle. Rather, it is caused by the brow lowering muscles often paired with nose wrinkler: depressor supercilii and procerus. There is variable interconnectivity between these muscles and the LLSAN.

AU10 – upper lip raiser

levator labii superioris

AU10 ACTION: Upper lip raiser lifts top lip (in a more lateral manner than nose wrinkler).

NOTE: For help differentiating between upper lip raiser and nasolabial furrow deepener: (1) If you are a subscriber view: Upper Lip Raiser vs. Nasolabial Furrow Deepener. (2) If you are not a subscriber, you can view the preview post of Upper Lip Raiser vs. Nasolabial Furrow Deepener here.

AU11 – nasolabial furrow deepener

zygomaticus minor

AU11 ACTION: Nasolabial furrow deepener lifts and stretches the top lip (in a more lateral and oblique manner than nose wrinkler or upper lip raiser).

NOTE: For help differentiating between upper lip raiser and nasolabial furrow deepener: (1) If you are a subscriber view: Upper Lip Raiser vs. Nasolabial Furrow Deepener. (2) If you are not a subscriber, you can view the preview post of Upper Lip Raiser vs. Nasolabial Furrow Deepener here.

AU38 – nostril dilator

dilator naris (alar portion of nasalis) 

AU38 ACTION: Nostril dilator expands / widens the nostril wings allowing for deeper air intake.

AU39 – nostril compressor

compressor naris (tranverse portion of nasalis)+ depressor septi

AU39 ACTION: Nostril compressor narrows the nostril wings while also often lowering the nose tip.

LIP CORNER MOVERS

FACS name

muscle name

expression reference

AU12 – lip corner puller

zygomaticus major

AU12 ACTION: Lip corner puller draws the lip corners up, back, and laterally.

AU13 – sharp lip puller

levator anguli oris

AU13 ACTION: Sharp lip puller (formerly known as cheek puffer) draws the lip corners upward.

AU14 -dimpler

partially #notFACS

 See “NOTE” below.

buccinator

y-axis type

z-axis type

AU14-y ACTION: Dimpler of the y-axis type pinches the lip corners against each other on a vertical plane.

AU14-z ACTION: Dimpler of the z-axis type pinches and pushes the lip corners back against the teeth

NOTE: y-axis and z-axis dimplers are not FACS-official terms. Classic FACS describes the z-axis type. Learn why I’ve coined y and z distinctions here.

AU15 – lip corner depressor

depressor anguli oris

AU15 ACTION: Lip corner depressor draws the lip corners downward.

AU18 – lip pucker

incisivus labii inferioris & incisivus labii superioris

AU18 ACTION: Lip pucker draws the lip corners medially.

NOTE 1: Incisivus labii superioris and incisivus labii inferioris are considered accessory muscles to orbicularis oris.

NOTE 2: Lip pucker typically co-activates vertical lip tightener (as seen in this example). Learn more about vertical lip tightener under the “ORBICULARIS ORIS ACTIONS” section below.

AU20 – lip stretcher

risorius

AU20 ACTION: Lip stretcher draws the lip corners laterally, stretching the lips.

NOTE1: Not to be confused with mouth stretch. Mouth stretch refers to forced (not due to relaxation) jaw lowering (see “JAW ACTIONS” section below).

NOTE2: Risorius is one of the most variable facial muscles in humans. Depending on the study, it has been reported missing in anywhere from 1-94% of research subjects. Risorius is narrow and difficult to locate; so it is possible that this discrepancy in statistics is partly inflated due to methodological study errors. For more on anatomical variation, book a studio lecture on facial muscle diversity. 

LOWER LIP & CHIN AREA

FACS name

muscle name

expression reference

AU16 – lower lip depressor

depressor labii inferioris

AU17 – chin raiser

mentalis

ORBICULARIS ORIS ACTIONS

FACS name

muscle name

expression reference

AU8 – lips toward each other

orbicularis oris

AU22 – lip funneler

orbicularis oris (peripheral portion)

AU23 – lip tightener

partially #notFACS

 See “NOTE” below.

orbicularis oris (marginal portion)

horizontal type

vertical type

NOTE: This 2-type distinction is a deviation from official FACS. Only “horizontal type” qualifies as lip tightener in original FACS. I have chosen to divide lip tightener into two types, because the lips tighten in distinct manners. The muscle behind both movements, orbicularis oris, possesses rich variation in fiber directionality; such directional variation yields more potential actions for orbicularis oris than have thus far been documented. The distinction of horizontal vs. vertical lip tightening proves especially useful when breaking down speech. For speech references, visit the Viseme Cheat Sheet.

AU24 – lip presser

orbicularis oris (marginal portion)

Read about lip presser asymmetries in speech here: M-B-P Bilabial Visemes. (Useful for those working on lipsync and automated speech solutions.)

AU28 – lips suck

orbicularis oris (marginal and peripheral portions)

NOTE 1: AU17 – chin raiser appears during the in-between steps. I cannot perform this action without assistance from AU17 during the transition to the final pose. Mentalis appearance during lips suck is likely the case for many others as well.

NOTE 2: Jaw drop is almost always required for lips suck.

JAW ACTIONS

FACS name

muscle name

expression reference

AU26 – jaw drop

masseter, relaxed temporalis and relaxed internal pterygoid

AU27 – mouth stretch

pterygoids, digastric

AD29 – jaw thrust

pterygoids (& some masseter)

NOTE: “AD” refers to “action descriptor.” An action descriptor is basically a less fleshed out action unit (AU). ADs differ in that they function more as event descriptors.

AD30 – jaw sideways

pterygoids & temporalis

AU31 – jaw clencher

temporalis, masseter, pterygoids

MISCELLANEOUS ACTIONS

FACS name

muscle name

expression reference

AD19 – tongue show

it depends**

NOTE: “AD” refers to “action descriptor.” An action descriptor is basically a less fleshed out action unit (AU). ADs differ in that they function more as event descriptors. In this case, AD19 – tongue show, simply means the tongue is protruding in a notable way beyond typical protrusion for speech, eating, breathing, etc. For a deep dive into tongue actions and tongue-related muscles, book a mini course on tongue movements and tongue anatomy.

AU21 – neck tightener

platysma

NOTE: You may see some AU20 – lip stretcher in the AU21 – neck tightener example and vice versa. This concurrence is due to a close relationship between the risorius and platysma muscles.

AU25 – lips part

it depends**

NOTE: In FACS, AU25 – lips part, refers to the state of the lips being parted. This parting can be caused by any action that separates the lips – e.g. relaxation of mentalis, relaxation of orbicularis oris, contraction of other muscles, etc.

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