Expressions

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An example of Expressions menu in the Action Menu.

Expressions are a feature of VRChat avatars, consisting of user-customized menus that let you enable actions or toggles on your avatar; designed for flexible, easy access to unique avatar features.

More information is available at Avatar Creators Docs.

Expressions menu

The in-game Expressions menu is accessible through the Action Menu, or the Expressions wing on the Quick Menu and Main Menu. in any version of VRChat. Changes to an avatar's expressions are networked globally to other users on the same platform, and can be set-up for cross-platform synchronization.

Expressions in the SDK

Expressions are edited using various parameters in the VRChat SDK.

Base expressions

When no expressions are configured, a default expression menu with base animations is added to the avatar, containing the following animations:

• Wave
• Clap
• Point
• Cheer
• Dance
• Backflip
• Die
• Sadness

Custom expressions

To add custom expressions, create an Expression Menu asset and an Expression Parameters asset in Unity, then assign them in the Expressions section of the VRChat Avatar Descriptor. The menu defines which controls appear in the in-game menu, while the parameters asset defines the names, types, default values, and synchronization behavior of the values those controls change.

Each custom parameter can be marked as Saved and Synced. Synced custom parameters count toward the avatar's 256-bit sync budget, while avatars can define up to 8192 total custom parameters. Parameters on this asset can also be changed by Contact Receivers, parameter drivers, PhysBones, and OSC.

The SDK also includes a Default Parameters button. This restores the three alias parameters used by VRChat's default AV3 controllers: VRCEmote, VRCFaceBlendH, and VRCFaceBlendV.

Controls

You can create up to 8 controls per page. When creating a control, choose its type:

• Button sets a value while pressed, then resets after VRChat sends the change.
• Toggle sets a value when enabled and resets it when disabled.
• Sub Menu opens another Expressions menu, and can optionally set a parameter while that submenu is open.
• Two Axis Puppet drives two float parameters from horizontal and vertical input, usually in the range -1.0 to 1.0.
• Four Axis Puppet drives four float parameters, one for each direction, usually in the range 0.0 to 1.0.
• Radial Puppet drives one float parameter from 0.0 to 1.0.

Puppet Menu Example

Example of the Action Menu and Face Mirror in use. (Animated GIF)

As you move your joystick, touchpad, or mouse in different directions, you change animation parameters to blend between moods (e.g., "happy" and "surprised"). Any parameter can be controlled from this menu.

You can open one menu on either hand (or both). By default, flick to select an option. In Action Menu settings, you can choose to use the Trigger. To back out of a selection in the Expressions menu, pull the trigger.

When a puppet control is open, VRChat synchronizes its live values with the faster IK sync mode. After it is closed, the frozen value remains until it is changed again.

Expression Parameter

Expression Parameters are used to control avatar features via expression menu, contact receiver, OSC, parameter drivers or physbones. These parameters are then mapped to Animator Controller parameters in your avatar's FX, Gesture, or Action controllers.

Settings

Each entry in the Expression Parameters asset stores:

• Name, which must match the Animator parameter name exactly.
• Type, which can be Bool, Int, or Float.
• Default, which is used when the avatar is reset.
• Saved, which controls whether the value persists between sessions.
• Synced, which controls whether the value is sent to other users.

By default, custom parameter sync uses VRChat's Playable sync mode. Puppet controls temporarily use faster IK sync while they are actively open.

Built-in parameters

VRChat also provides built-in Animator parameters. These do not need to be added to the Expression Parameters asset, and they do not count toward the custom parameter budget.

Built-in parameters are read-only. They are added directly to a playable layer's Animator Controller by name, and VRChat updates them automatically at runtime. They are not set on sub-animators, only on playable-layer animators.

Additional built-in parameters include:

• Viseme (Int) — Set by lip sync from 0 (silence) to 14 (the "u" vowel) when the Avatar Descriptor's Lip Sync is set to Viseme Blend Shape or Viseme Parameter Only.
• Voice (Float) — Perceived microphone volume from 0.0 to 1.0, affected by distance and earmuff settings.
• VelocityX, VelocityY, VelocityZ, VelocityMagnitude (Float) — Movement speed in m/s along each axis and total magnitude. Locally, playspace movement does not count; remotely, it does.
• Upright (Float) — 0 when prone, 1 when standing.
• Grounded (Bool) — Whether the user is touching the ground.
• MuteSelf (Bool) — Whether the user's microphone is muted.
• Earmuffs (Bool) — Whether the user has earmuffs enabled.
• IsOnFriendsList (Bool) — Whether the viewer is friends with the avatar's wearer (shows False locally).
• ScaleFactor, ScaleFactorInverse, EyeHeightAsMeters, EyeHeightAsPercent (Float) — Scaling-related parameters for avatar scaling. EyeHeightAsMeters is recommended for scale-aware systems because it is linear and does not depend on upload height.

Each built-in parameter has a sync type determining when it is sent to remote users: IK for tracking-derived values (gestures, velocity, grounded), Speech for voice-related values (viseme, voice), Playable for user-state values (mute, earmuffs, tracking type, scale), or None for local-only values (IsLocal, PreviewMode).

Network synchronization

Only synced expression parameters and certain built-in parameters are sent over the network. The full list of data sent for each avatar includes:

• IK targets — Head, jaw, and hands for desktop and 3-point tracking; additionally hip and feet for full-body tracking. Index controller users also sync finger positions.
• Synced expression parameters — Only parameters marked as Synced are transmitted. Values are quantized: Int values sync in the range 0–255, Float values sync as multiples of 1/127 between −1 and 1, and Bools sync as true or false.
• Built-in VRC parameters — Including gestures, velocity, voice, and other runtime parameters.
• PhysBones — Pose position data is sent to late joiners.

For reliable late-joiner support, a recommended pattern is to split animator logic using the IsLocal parameter: local-side layers handle contacts, parameter drivers, and all logic, then set synced parameters, while remote-side layers only read those synced parameters to play the correct visualization.

Gestures and facial expressions

The built-in GestureLeft and GestureRight parameters identify the user's hand gesture, while GestureLeftWeight and GestureRightWeight expose analog trigger pressure. On humanoid avatars, the Gesture playable layer is commonly used for hand poses, while facial expressions are often driven from the FX layer with blendshapes, material properties, or other non-humanoid animations.

On tracked controllers where finger tracking overrides animation by default, creators can use a Tracking Control state behavior to switch the relevant fingers from Tracking to Animation when needed.

Expression Parameter Mismatching

Expression Parameter Mismatching refers to the practice of using different parameter types between your Expression Parameters and your local Animator Controller parameters. While it is recommended to keep parameter types consistent, mismatching is supported and the system will convert values between types according to specific rules. This can be useful in certain advanced setups. The same conversion behavior can also be used with built-in VRChat Animator parameters.

Unity's Animator system uses floats on the backend for all parameter types, while VRChat stores synced custom parameters in compact network-friendly formats. The user interface in Unity and the VRCSDK lets creators choose parameter types for convenience, but under the hood, value conversion is possible. This means that parameters are not being cast in the C# sense, but rather mismatched across systems. This behavior is also supported by popular tools such as Av3Emulator and Gesture Manager.

Expression Parameter Bool

Animator Controller Parameter

Type	Expression Bool = False	Expression Bool = True
Bool → Bool	Bool = False	Bool = True
Bool → Int	Int = 0	Int = 1
Bool → Float	Float = 0.0	Float = 1.0

Expression Parameter Int

Animator Controller Parameter

Type	Behaviour
Int → Bool	Any Int value that isn't 0 sets bool to True
Int → Int	Expected Behaviour
Int → Float	Straight Conversion: e.g. Int = 2 → Float = 2.0

Expression Parameter Float

Animator Controller Parameter

Type	Behaviour
Float → Bool	Any Float value that isn't 0 sets bool to True
Float → Int	Rounded Conversion: ≥0.5 → 1 ; <0.5 → 0
Float → Float	Expected Behaviour

Resources

• Avatar 3.0 Hub world on VRChat
• Expression Menu and Controls on Creator Docs
• Action Menu - Expression Menu on Creator Docs
• Animator Parameters on Creator Docs
• Playable Layers on Creator Docs
• State Behaviors on Creator Docs

See also

• Avatars
  • Avatar Dynamics
• Action Menu
• VRChat SDK

References

• VRC School: Expressions Menu and Parameters
• VRC School: Hand Gestures/Facial Expressions
• VRC School: Built-In VRC Parameters
• VRC School: Network Sync
• VRC School: Expression Parameter Mismatching