diff --git a/Assets/UniGLTF/Runtime/Extensions/StringExtensions.cs b/Assets/UniGLTF/Runtime/Extensions/StringExtensions.cs
index 92dbdbb7e..62e3b7170 100644
--- a/Assets/UniGLTF/Runtime/Extensions/StringExtensions.cs
+++ b/Assets/UniGLTF/Runtime/Extensions/StringExtensions.cs
@@ -35,13 +35,13 @@ namespace UniGLTF
 
         public static bool StartsWithUnityAssetPath(this string path)
         {
-            return path.Replace("\\", "/").StartsWith(UnityBasePath + "/Assets");
+            return path.Replace("\\", "/").FastStartsWith(UnityBasePath + "/Assets");
         }
 
         public static string ToUnityRelativePath(this string path)
         {
             path = path.Replace("\\", "/");
-            if (path.StartsWith(UnityBasePath))
+            if (path.FastStartsWith(UnityBasePath))
             {
                 return path.Substring(UnityBasePath.Length + 1);
             }
@@ -72,5 +72,42 @@ namespace UniGLTF
             }
             return path;
         }
+
+        // https://docs.unity3d.com/Manual/BestPracticeUnderstandingPerformanceInUnity5.html
+        public static bool FastStartsWith(this string a, string b)
+        {
+            var aLen = a.Length;
+            var bLen = b.Length;
+            if (aLen < bLen)
+            {
+                return false;
+            }
+
+            var p = 0;
+            while (p < bLen && a[p] == b[p])
+            {
+                ++p;
+            }
+
+            return p == bLen;
+        }
+
+        public static bool FastEndsWith(this string a, string b)
+        {
+            var aLen = a.Length;
+            var bLen = b.Length;
+            if (aLen < bLen)
+            {
+                return false;
+            }
+
+            var p = 1;
+            while (p <= bLen && a[aLen - p] == b[bLen - p])
+            {
+                ++p;
+            }
+
+            return p - 1 == bLen;
+        }
     }
 }
diff --git a/Assets/UniGLTF/Runtime/Extensions/glTFExtensions.cs b/Assets/UniGLTF/Runtime/Extensions/glTFExtensions.cs
index 526706773..e93568cd3 100644
--- a/Assets/UniGLTF/Runtime/Extensions/glTFExtensions.cs
+++ b/Assets/UniGLTF/Runtime/Extensions/glTFExtensions.cs
@@ -368,7 +368,7 @@ namespace UniGLTF
             }
             else
             {
-                if (image.uri.StartsWith("data:"))
+                if (image.uri.FastStartsWith("data:"))
                 {
                     textureName = !string.IsNullOrEmpty(image.name) ? image.name : string.Format("{0:00}#Base64Embedded", imageIndex);
                 }
diff --git a/Assets/UniGLTF/Runtime/UniGLTF/Format/glTFTexture.cs b/Assets/UniGLTF/Runtime/UniGLTF/Format/glTFTexture.cs
index 20d3a8be2..b04b2549c 100644
--- a/Assets/UniGLTF/Runtime/UniGLTF/Format/glTFTexture.cs
+++ b/Assets/UniGLTF/Runtime/UniGLTF/Format/glTFTexture.cs
@@ -58,11 +58,11 @@ namespace UniGLTF
                     return ".jpg";
 
                 default:
-                    if (uri.StartsWith("data:image/jpeg;"))
+                    if (uri.FastStartsWith("data:image/jpeg;"))
                     {
                         return ".jpg";
                     }
-                    else if (uri.StartsWith("data:image/png;"))
+                    else if (uri.FastStartsWith("data:image/png;"))
                     {
                         return ".png";
                     }
diff --git a/Assets/UniGLTF/Runtime/UniGLTF/IO/AnimationExporter.cs b/Assets/UniGLTF/Runtime/UniGLTF/IO/AnimationExporter.cs
index d30c21378..4a55e5d64 100644
--- a/Assets/UniGLTF/Runtime/UniGLTF/IO/AnimationExporter.cs
+++ b/Assets/UniGLTF/Runtime/UniGLTF/IO/AnimationExporter.cs
@@ -65,23 +65,23 @@ namespace UniGLTF
 
         public static glTFAnimationTarget.AnimationProperties PropertyToTarget(string property)
         {
-            if (property.StartsWith("m_LocalPosition."))
+            if (property.FastStartsWith("m_LocalPosition."))
             {
                 return glTFAnimationTarget.AnimationProperties.Translation;
             }
-            else if (property.StartsWith("localEulerAnglesRaw."))
+            else if (property.FastStartsWith("localEulerAnglesRaw."))
             {
                 return glTFAnimationTarget.AnimationProperties.EulerRotation;
             }
-            else if (property.StartsWith("m_LocalRotation."))
+            else if (property.FastStartsWith("m_LocalRotation."))
             {
                 return glTFAnimationTarget.AnimationProperties.Rotation;
             }
-            else if (property.StartsWith("m_LocalScale."))
+            else if (property.FastStartsWith("m_LocalScale."))
             {
                 return glTFAnimationTarget.AnimationProperties.Scale;
             }
-            else if (property.StartsWith("blendShape."))
+            else if (property.FastStartsWith("blendShape."))
             {
                 return glTFAnimationTarget.AnimationProperties.BlendShape;
             }
@@ -97,7 +97,7 @@ namespace UniGLTF
             {
                 return 0;
             }
-            if (property.EndsWith(".y") || property.StartsWith("blendShape."))
+            if (property.EndsWith(".y") || property.FastStartsWith("blendShape."))
             {
                 return 1;
             }
diff --git a/Assets/UniGLTF/Runtime/UniGLTF/IO/FileSystemStorage.cs b/Assets/UniGLTF/Runtime/UniGLTF/IO/FileSystemStorage.cs
index c2c07932b..99961fea8 100644
--- a/Assets/UniGLTF/Runtime/UniGLTF/IO/FileSystemStorage.cs
+++ b/Assets/UniGLTF/Runtime/UniGLTF/IO/FileSystemStorage.cs
@@ -39,7 +39,7 @@ namespace UniGLTF
         public ArraySegment<byte> Get(string url)
         {
             var bytes =
-                (url.StartsWith("data:"))
+                (url.FastStartsWith("data:"))
                 ? UriByteBuffer.ReadEmbedded(url)
                 : File.ReadAllBytes(Path.Combine(m_root, url))
                 ;
@@ -48,7 +48,7 @@ namespace UniGLTF
 
         public string GetPath(string url)
         {
-            if (url.StartsWith("data:"))
+            if (url.FastStartsWith("data:"))
             {
                 return null;
             }
diff --git a/Assets/UniGLTF/Runtime/UniGLTF/IO/ImporterContext.cs b/Assets/UniGLTF/Runtime/UniGLTF/IO/ImporterContext.cs
index 906cdeba6..d32b9af49 100644
--- a/Assets/UniGLTF/Runtime/UniGLTF/IO/ImporterContext.cs
+++ b/Assets/UniGLTF/Runtime/UniGLTF/IO/ImporterContext.cs
@@ -165,7 +165,7 @@ namespace UniGLTF
         {
             if (string.IsNullOrEmpty(generatorVersion)) return false;
             if (generatorVersion == "UniGLTF") return true;
-            if (!generatorVersion.StartsWith("UniGLTF-")) return false;
+            if (!generatorVersion.FastStartsWith("UniGLTF-")) return false;
 
             try
             {
@@ -475,7 +475,7 @@ namespace UniGLTF
                 var image = GLTF.GetImageFromTextureIndex(i);
                 if (imageBaseDir.IsUnderAssetsFolder
                     && !string.IsNullOrEmpty(image.uri)
-                    && !image.uri.StartsWith("data:")
+                    && !image.uri.FastStartsWith("data:")
                     )
                 {
                     ///
diff --git a/Assets/UniGLTF/Runtime/UniGLTF/IO/UnityPath.cs b/Assets/UniGLTF/Runtime/UniGLTF/IO/UnityPath.cs
index 9a4cebe0d..11cccb200 100644
--- a/Assets/UniGLTF/Runtime/UniGLTF/IO/UnityPath.cs
+++ b/Assets/UniGLTF/Runtime/UniGLTF/IO/UnityPath.cs
@@ -40,7 +40,7 @@ namespace UniGLTF
                 {
                     return false;
                 }
-                return Value == "Assets" || Value.StartsWith("Assets/");
+                return Value == "Assets" || Value.FastStartsWith("Assets/");
             }
         }
 
@@ -53,7 +53,7 @@ namespace UniGLTF
                     return false;
                 }
 
-                return FullPath.StartsWith(Application.streamingAssetsPath + "/");
+                return FullPath.FastStartsWith(Application.streamingAssetsPath + "/");
             }
         }
 
@@ -276,7 +276,7 @@ namespace UniGLTF
                     Value = ""
                 };
             }
-            else if (fullPath.StartsWith(BaseFullPath + "/"))
+            else if (fullPath.FastStartsWith(BaseFullPath + "/"))
             {
                 return new UnityPath(fullPath.Substring(BaseFullPath.Length + 1));
             }
@@ -288,7 +288,7 @@ namespace UniGLTF
 
         public static bool IsUnderAssetFolder(string fullPath)
         {
-            return fullPath.Replace("\\", "/").StartsWith(AssetFullPath);
+            return fullPath.Replace("\\", "/").FastStartsWith(AssetFullPath);
         }
         #endregion
 
diff --git a/Assets/VRM/Runtime/IO/VRMImporterContext.cs b/Assets/VRM/Runtime/IO/VRMImporterContext.cs
index 5c018092f..4bb9f6c6c 100644
--- a/Assets/VRM/Runtime/IO/VRMImporterContext.cs
+++ b/Assets/VRM/Runtime/IO/VRMImporterContext.cs
@@ -150,7 +150,7 @@ namespace VRM
             var asset = ScriptableObject.CreateInstance<BlendShapeClip>();
             var groupName = group.name;
             var prefix = "BlendShape.";
-            while (groupName.StartsWith(prefix))
+            while (groupName.FastStartsWith(prefix))
             {
                 groupName = groupName.Substring(prefix.Length);
             }
@@ -195,8 +195,8 @@ namespace VRM
 
                     var material = GetMaterials().FirstOrDefault(y => y.name == x.materialName);
                     var propertyName = x.propertyName;
-                    if (x.propertyName.EndsWith("_ST_S")
-                    || x.propertyName.EndsWith("_ST_T"))
+                    if (x.propertyName.FastEndsWith("_ST_S")
+                    || x.propertyName.FastEndsWith("_ST_T"))
                     {
                         propertyName = x.propertyName.Substring(0, x.propertyName.Length - 2);
                     }