diff --git a/Packages/nadena.dev.modular-avatar/Editor/AvatarProcessor.cs b/Packages/nadena.dev.modular-avatar/Editor/AvatarProcessor.cs
index 6417e2fd..66cc997d 100644
--- a/Packages/nadena.dev.modular-avatar/Editor/AvatarProcessor.cs
+++ b/Packages/nadena.dev.modular-avatar/Editor/AvatarProcessor.cs
@@ -188,6 +188,8 @@ namespace nadena.dev.modular_avatar.core.editor
 
                     context.AnimationDatabase.Commit();
 
+                    new GCGameObjectsPass(context, avatarGameObject).OnPreprocessAvatar();
+
                     AfterProcessing?.Invoke(avatarGameObject);
                 }
                 finally
diff --git a/Packages/nadena.dev.modular-avatar/Editor/OptimizationPasses.meta b/Packages/nadena.dev.modular-avatar/Editor/OptimizationPasses.meta
new file mode 100644
index 00000000..bd8c2f7e
--- /dev/null
+++ b/Packages/nadena.dev.modular-avatar/Editor/OptimizationPasses.meta
@@ -0,0 +1,4 @@
+fileFormatVersion: 2
+guid: 2f3bf44d18c6489ab4425ec3cdee360d
+timeCreated: 1677488644
+folderAsset: yes
\ No newline at end of file
diff --git a/Packages/nadena.dev.modular-avatar/Editor/OptimizationPasses/GCGameObjectsPass.cs b/Packages/nadena.dev.modular-avatar/Editor/OptimizationPasses/GCGameObjectsPass.cs
new file mode 100644
index 00000000..dc0a19a9
--- /dev/null
+++ b/Packages/nadena.dev.modular-avatar/Editor/OptimizationPasses/GCGameObjectsPass.cs
@@ -0,0 +1,170 @@
+using System;
+using System.Collections.Generic;
+using UnityEditor;
+using UnityEngine;
+using VRC.SDK3.Dynamics.PhysBone.Components;
+
+namespace nadena.dev.modular_avatar.core.editor
+{
+    /// <summary>
+    /// Remove all GameObjects which have no influence on the avatar.
+    /// </summary>
+    internal class GCGameObjectsPass
+    {
+        private readonly BuildContext _context;
+        private readonly GameObject _root;
+        private readonly HashSet<GameObject> referencedGameObjects = new HashSet<GameObject>();
+
+        internal GCGameObjectsPass(BuildContext context, GameObject root)
+        {
+            _context = context;
+            _root = root;
+        }
+
+        internal void OnPreprocessAvatar()
+        {
+            MarkAll();
+            Sweep();
+        }
+
+        private void MarkAll()
+        {
+            foreach (var obj in GameObjects(_root,
+                         node =>
+                         {
+                             if (node.CompareTag("EditorOnly"))
+                             {
+                                 if (EditorApplication.isPlayingOrWillChangePlaymode)
+                                 {
+                                     // Retain EditorOnly objects (in case they contain camera fixtures or something),
+                                     // but ignore references _from_ them. (TODO: should we mark from them as well?)
+                                     MarkObject(node);
+                                 }
+
+                                 return false;
+                             }
+
+                             return true;
+                         }
+                     ))
+            {
+                foreach (var component in obj.GetComponents<Component>())
+                {
+                    switch (component)
+                    {
+                        case Transform t: break;
+
+                        case VRCPhysBone pb:
+                            MarkObject(obj);
+                            MarkPhysBone(pb);
+                            break;
+
+                        case AvatarTagComponent _:
+                            // Tag components will not be retained at runtime, so pretend they're not there.
+                            break;
+
+                        default:
+                            MarkObject(obj);
+                            MarkAllReferencedObjects(component);
+                            break;
+                    }
+                }
+            }
+        }
+
+        private void MarkPhysBone(VRCPhysBone pb)
+        {
+            var rootTransform = pb.GetRootTransform();
+            var ignoreTransforms = pb.ignoreTransforms ?? new List<Transform>();
+
+            foreach (var obj in GameObjects(rootTransform.gameObject,
+                         obj => !obj.CompareTag("EditorOnly") && !ignoreTransforms.Contains(obj.transform)))
+            {
+                MarkObject(obj);
+            }
+
+            // Mark colliders, etc
+            MarkAllReferencedObjects(pb);
+        }
+
+        private void MarkAllReferencedObjects(Component component)
+        {
+            var so = new SerializedObject(component);
+            var sp = so.GetIterator();
+
+            bool enterChildren = true;
+            while (sp.Next(enterChildren))
+            {
+                enterChildren = true;
+
+                switch (sp.propertyType)
+                {
+                    case SerializedPropertyType.String:
+                        enterChildren = false;
+                        continue;
+                    case SerializedPropertyType.ObjectReference:
+                        if (sp.objectReferenceValue != null)
+                        {
+                            if (sp.objectReferenceValue is GameObject refObj)
+                            {
+                                MarkObject(refObj);
+                            }
+                            else if (sp.objectReferenceValue is Component comp)
+                            {
+                                MarkObject(comp.gameObject);
+                            }
+                        }
+
+                        break;
+                }
+            }
+        }
+
+        private void MarkObject(GameObject go)
+        {
+            while (go != null && referencedGameObjects.Add(go) && go != _root)
+            {
+                go = go.transform.parent?.gameObject;
+            }
+        }
+
+        private void Sweep()
+        {
+            foreach (var go in GameObjects())
+            {
+                if (!referencedGameObjects.Contains(go))
+                {
+                    Debug.Log("Purging object: " + RuntimeUtil.AvatarRootPath(go));
+                    UnityEngine.Object.DestroyImmediate(go);
+                }
+            }
+        }
+
+        private IEnumerable<GameObject> GameObjects(GameObject node = null,
+            Func<GameObject, bool> shouldTraverse = null)
+        {
+            if (node == null) node = _root;
+            if (shouldTraverse == null) shouldTraverse = obj => !obj.CompareTag("EditorOnly");
+
+            if (!shouldTraverse(node)) yield break;
+
+            yield return node;
+            if (node == null) yield break;
+
+            // Guard against object deletion mid-traversal
+            List<Transform> children = new List<Transform>();
+            foreach (Transform t in node.transform)
+            {
+                children.Add(t);
+            }
+
+            foreach (var child in children)
+            {
+                foreach (var grandchild in GameObjects(child.gameObject, shouldTraverse))
+                {
+                    yield return grandchild;
+                }
+            }
+        }
+    }
+}
\ No newline at end of file
diff --git a/Packages/nadena.dev.modular-avatar/Editor/OptimizationPasses/GCGameObjectsPass.cs.meta b/Packages/nadena.dev.modular-avatar/Editor/OptimizationPasses/GCGameObjectsPass.cs.meta
new file mode 100644
index 00000000..db4e3c5d
--- /dev/null
+++ b/Packages/nadena.dev.modular-avatar/Editor/OptimizationPasses/GCGameObjectsPass.cs.meta
@@ -0,0 +1,3 @@
+fileFormatVersion: 2
+guid: 3c155e44d9874f2ba44e67f129112d63
+timeCreated: 1677488653
\ No newline at end of file