Human Rig Bone Names and Standard Skeleton Hierarchy

Intro

Human rig bone naming is the process of assigning clear and consistent names to the bones of a character skeleton.

Standardized bone names improve animation retargeting, compatibility between software packages, and collaboration between artists. They are commonly used in Blender, Maya, Unity, Unreal Engine, VRChat, Mixamo, and VRM character pipelines.

This guide includes a complete human rig bone names list, a standard skeleton hierarchy, production naming conventions, and platform-specific requirements for humanoid rigs.

Skeleton vs Rig in Character Animation

In character animation, a skeleton and a rig are closely related, but they are not the same thing.

A skeleton is the internal hierarchy of bones or joints inside a 3D character. It defines the body structure, joint placement, and how the main body parts are connected. In many 3D workflows, the terms “bone” and “joint” are often used interchangeably, although technically a joint is a pivot point and a bone is the segment between two joints.

A rig is the complete animation control system built on top of the skeleton. It usually includes the skeleton, animation controls, constraints, inverse kinematics (IK), forward kinematics (FK), skinning, deformation setup, helper bones, twist bones, and custom controls for animators.

Clean bone names are important because animation tools and retargeting systems need a predictable structure. Standardized naming and humanoid mapping systems, such as Unity Humanoid, VRChat, and VRM, help software recognize body parts and apply animations or motion capture data to different characters more reliably.

Good bone naming also makes the rig easier to debug, mirror, export, retarget, and share between Blender, Maya, Unity, Unreal Engine, VRChat, Mixamo, and VRM pipelines.

Human Rig Bone Names List

The table below shows common humanoid rig bone names and their production-friendly equivalents. These names are not mandatory in every software package, but they are widely used in game-ready character rigs, animation rigs, and humanoid avatar pipelines.

Standard Human Rig Skeleton Structure

Example of a standard human rig skeleton hierarchy used in Unity, Unreal Engine, Blender, VRChat, and VRM character rigs.

root
└─ pelvis
   ├─ spine_01
   │  └─ spine_02
   │     └─ spine_03
   │        ├─ clavicle_l
   │        │  └─ upperarm_l
   │        │     └─ lowerarm_l
   │        │        └─ hand_l
   │        └─ clavicle_r
   │           └─ upperarm_r
   │              └─ lowerarm_r
   │                 └─ hand_r
   │
   ├─ thigh_l
   │  └─ calf_l
   │     └─ foot_l
   │        └─ ball_l
   │
   └─ thigh_r
      └─ calf_r
         └─ foot_r
            └─ ball_r

This hierarchy is a simplified game-ready skeleton example. Production rigs may include extra twist bones, finger bones, facial bones, IK targets, and helper bones depending on the animation pipeline.

Blender Bone Naming Convention

In Blender, a character skeleton is stored inside an Armature, and the individual skeletal elements are called bones. For left and right body parts, Blender commonly uses .L and .R suffixes.

For example:

• upper_arm.L
• forearm.L
• hand.L
• upper_arm.R
• forearm.R
• hand.R

This naming style helps Blender recognize symmetrical bones and makes it easier to mirror, flip, and edit armatures.

Blender vs Production Bone Names

Different pipelines may use different bone naming styles for the same body parts.

The important thing is to understand the difference between a bone name and a humanoid slot.

A bone name is the actual name inside your Blender armature or FBX file, such as upperarm_l, lowerarm_l, or hand_l.

A humanoid slot is the body-part field used by systems like Unity Humanoid, VRChat, or VRM. For example, upperarm_l can be mapped to the Left Upper Arm slot, and hand_l can be mapped to the Left Hand slot.

So your bones do not always need to be named exactly like Unity or VRChat slots. However, clean and predictable names make the rig easier to mirror, export, retarget, debug, and share between different tools.

If the character will stay mostly inside Blender, .L and .R names are convenient. If the character is prepared for a game engine or FBX pipeline, _l and _r names are often easier to keep consistent.

Unity Humanoid Bone Names

Unity Humanoid uses a standardized Avatar Mapping system that allows animations to be retargeted between different character rigs. Unlike Generic rigs, Humanoid avatars do not require specific bone names as long as the skeleton can be correctly mapped to Unity’s humanoid bone slots.

During avatar setup, Unity assigns your rig bones to predefined slots such as Hips, Spine, Chest, Head, Upper Arm, Lower Arm, Hand, Upper Leg, and Foot. Once the mapping is completed, the character can use any Humanoid-compatible animation.

Unity Humanoid Avatar Bone Mapping

The Unity Humanoid Avatar system uses predefined bone slots rather than requiring exact bone names.

Required Unity Humanoid Slots

The following bone slots are required for a valid Unity Humanoid avatar and animation retargeting.

Optional Unity Humanoid Slots

While not always required, these bones improve animation quality and support additional Humanoid features.

Unity Bone Mapping Example

A typical production rig can use completely different bone names while still being recognized as a Unity Humanoid avatar. 

• pelvis → Hips
• spine_01 → Spine
• spine_02 → Chest
• head → Head
• upperarm_l → Left Upper Arm
• hand_l → Left Hand

This is only a short mapping example. A full bone list is provided in the Human Rig Bone Names List section above.

Unity Humanoid Bone Naming Tips

VRChat Bone Names

VRChat avatars use Unity’s Humanoid rig system, so VRChat does not require a separate bone naming convention. The most important part is that the avatar skeleton is correctly mapped as a Humanoid avatar inside Unity.

This means that production bone names such as pelvis, spine_01, upperarm_l, hand_l, thigh_l, and foot_l can work in VRChat as long as they are assigned to the correct Unity Humanoid slots.

VRChat Avatar Bone Setup

For a VRChat avatar, focus on correct humanoid mapping first and clean production names second. The main body bones should be easy to identify, correctly parented, and assigned to the right Unity Humanoid slots.

A practical VRChat-ready skeleton usually includes:

Clear production names make the avatar easier to debug in Unity, especially when checking Humanoid Avatar Configuration, hand gestures, full-body tracking, and animation retargeting.

Optional VRChat Bones for Better Animation

While the main Humanoid mapping is the most important part, additional bones can improve avatar movement, gestures, tracking, and facial features.

VRChat Bone Naming Tips

VRChat does not care whether your FBX bones are named exactly Hips, LeftUpperArm, or LeftHand. What matters is that the bones are correctly assigned in Unity’s Humanoid Avatar Configuration.

However, clear production names such as pelvis, spine_01, upperarm_l, lowerarm_l, hand_l, thigh_l, calf_l, and foot_l make the rig easier to debug, edit, and share with other artists.

VRM Humanoid Bone Names

VRM avatars use a standardized humanoid structure, similar to Unity Humanoid and VRChat avatars. The exact FBX bone names can vary, but the bones must be correctly assigned to humanoid body slots.

A VRM-ready character can use clean production bone names such as pelvis, spine_01, spine_02, neck_01, head, upperarm_l, lowerarm_l, hand_l, thigh_l, calf_l, foot_l, and ball_l.

VRM Humanoid Mapping Example

For VRM avatars, consistent naming is especially useful when preparing VTuber models, motion capture workflows, facial expressions, spring bones, and cross-application humanoid animation.

Hand and Finger Bone Names

Finger bones are not always required for a basic humanoid rig, but they are important for hand animation, VRChat gestures, VRM avatars, motion capture cleanup, and expressive character posing.

A common production naming convention uses three bones per finger: base, middle, and tip.

Some pipelines use little instead of pinky, or proximal, intermediate, and distal instead of “01”, “02”, and “03”. The exact naming style can vary, but the most important rule is consistency.

For example, do not mix thumb_01_l, index_proximal_L, and middle1Left in the same rig unless your pipeline specifically requires it.

Frequently Asked Questions