VTuber Model Mouth Not Moving

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VTuber Model Mouth Not Moving

How to Fix VTuber Lip Sync Issues Step by Step (PNGTuber, Live2D, 3D)

A VTuber model’s mouth not moving is one of the most common—and most frustrating—problems creators face.
Your avatar looks fine, tracking seems active, audio works, yet the mouth stays closed or barely reacts when you speak.

This issue instantly breaks immersion, makes the model feel lifeless, and signals “technical problems” to viewers—even if everything else looks polished.

This guide explains exactly why VTuber mouths stop moving, how the issue differs by model type, and the precise fixes professionals use to restore natural, reliable lip sync.

What “VTuber Model Mouth Not Moving” Really Means

When creators report this issue, it usually falls into one of these cases:

  • Mouth does not move at all

  • Mouth moves only slightly

  • Mouth opens randomly, not matching speech

  • Mouth works in preview but not on stream

  • Mouth works sometimes, then stops

In almost all cases, the problem is setup-related, not model art quality.

Quick Diagnosis: Which Model Type Are You Using?

Before troubleshooting, identify your model type:

  • PNGTuber → Audio-reactive mouth

  • Live2D → Audio + tracking-driven mouth parameters

  • 3D (VRM / FBX) → Blendshapes or visemes

Each type fails for different reasons.

PNGTuber: Mouth Not Moving (Audio Reactive Issue)

PNGTubers rely entirely on audio input, not face tracking.

Common Causes

  • Wrong microphone selected

  • Audio filters blocking volume detection

  • Mic volume too low

  • Noise suppression cutting speech

  • OBS routing issues

Fix Checklist

  • Select the correct mic in PNGTuber software

  • Disable aggressive noise suppression

  • Increase mic gain slightly

  • Test with loud, clear speech

  • Verify audio meter is actively moving

If the audio meter moves, the mouth should move.

Live2D: Mouth Not Moving (Most Common Case)

Live2D mouth issues are usually calibration or parameter problems.

Most Common Causes

  • Mouth parameters not mapped correctly

  • Mouth sensitivity set too low

  • Neutral face incorrectly calibrated

  • Tracking input not detected

  • Audio input not assigned

Step 1: Confirm Tracking Input

In your tracking software (e.g. VTube Studio):

  • Confirm webcam or iPhone is detected

  • Check that face tracking is active

  • Verify audio input is selected

If tracking is inactive, mouth will not move.

Step 2: Recalibrate Neutral Face

Bad neutral calibration locks the mouth.

Fix by:

  • Relaxing your face

  • Closing mouth naturally

  • Re-calibrating neutral position

A bad neutral baseline makes the software think your mouth is already “open.”

Step 3: Increase Mouth Sensitivity

Default settings are often too low.

Adjust:

  • Mouth open threshold

  • Mouth strength / gain

  • Lip sync sensitivity

Test while speaking normally, not whispering.

Step 4: Check Mouth Parameters

If the model was rigged incorrectly, the mouth may exist but not respond.

Confirm:

  • Mouth open parameter exists

  • Visemes (A/I/U/E/O) are mapped

  • No conflicting parameter locks

If parameters are missing, this is a rigging issue, not setup.

3D VTuber: Mouth Not Moving (Blendshape Problem)

3D VTubers rely on blendshapes (visemes).

Common Causes

  • No visemes assigned

  • Incorrect blendshape naming

  • Audio input not linked

  • Low microphone sensitivity

  • Tracking software mismatch

Fix Steps

  • Open your tracking software (e.g. VSeeFace)

  • Check that visemes are detected

  • Speak and watch viseme indicators

  • Increase mic sensitivity

  • Test another mic if needed

If visemes never activate, the model may be missing required data.

OBS: Mouth Works in App but Not on Stream

This is extremely common.

Causes

  • Audio desync

  • Monitoring delay

  • Incorrect OBS audio source

  • Virtual cable issues

Fix

  • Match OBS audio sample rate with tracking software

  • Avoid audio monitoring unless needed

  • Ensure the same mic is used everywhere

  • Test recording, not just preview

OBS issues don’t stop mouth movement—they desync it, making it look broken.

Lighting Can Break Mouth Tracking

Poor lighting causes tracking failure even with good cameras.

Symptoms

  • Mouth flickers

  • Mouth stops moving randomly

  • Works only at certain angles

Fix

  • Light your face evenly

  • Avoid shadows under nose and mouth

  • Avoid strong backlight

  • Use consistent brightness

Lighting fixes more mouth issues than people expect.

Common Mistakes That Cause Mouth Issues

  • Speaking too quietly

  • Overusing noise suppression

  • Whispering during calibration

  • Using auto camera exposure

  • Using multiple audio filters

  • Calibrating while smiling

Calibrate calmly, speak clearly, test consistently.

Beginner vs Advanced Mouth Setup

Beginner

  • Webcam mic

  • Simple lip sync

  • Moderate sensitivity

  • Minimal filters

Advanced

  • Dedicated microphone

  • Tuned visemes

  • Profile-based mouth sensitivity

  • Separate presets for gaming vs chatting

Advanced setups focus on consistency, not exaggeration.

When It’s Actually a Rigging Problem

It is the model’s fault if:

  • Mouth parameters don’t exist

  • Visemes are missing

  • Mouth doesn’t respond in any software

  • Artist delivered incomplete files

In this case, contact the artist—not your settings.

VTuber Mouth Not Moving – Fix Checklist

✔ Correct mic selected
✔ Tracking input active
✔ Neutral face recalibrated
✔ Mouth sensitivity increased
✔ Audio filters simplified
✔ OBS audio synced
✔ Lighting corrected

If any box is unchecked, mouth issues will persist.

Final Thoughts

A VTuber model without mouth movement feels broken—even if everything else works.

Fixing a VTuber model mouth not moving is about:

  • Correct input

  • Proper calibration

  • Stable audio

  • Clean tracking conditions

Once fixed, your avatar becomes expressive, natural, and engaging—exactly what viewers expect from a professional VTuber.

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