diff --git a/src/libraries/System.Private.Uri/src/System/UriExt.cs b/src/libraries/System.Private.Uri/src/System/UriExt.cs
index 6f2f61c76721d..ee35d01e96232 100644
--- a/src/libraries/System.Private.Uri/src/System/UriExt.cs
+++ b/src/libraries/System.Private.Uri/src/System/UriExt.cs
@@ -1,6 +1,7 @@
 // Licensed to the .NET Foundation under one or more agreements.
 // The .NET Foundation licenses this file to you under the MIT license.
 
+using System.Buffers;
 using System.Diagnostics;
 using System.Diagnostics.CodeAnalysis;
 using System.Globalization;
@@ -216,32 +217,49 @@ private void InitializeUri(ParsingError err, UriKind uriKind, out UriFormatExcep
             }
         }
 
-        // Unescapes entire string and checks if it has unicode chars
-        // Also checks for sequences that are 3986 Unreserved characters as these should be un-escaped
+        /// <summary>SearchValues for all ASCII characters other than %</summary>
+        private static readonly SearchValues<char> s_asciiOtherThanPercent = SearchValues.Create(
+            "\u0000\u0001\u0002\u0003\u0004\u0005\u0006\u0007\u0008\u0009\u000A\u000B\u000C\u000D\u000E\u000F" +
+            "\u0010\u0011\u0012\u0013\u0014\u0015\u0016\u0017\u0018\u0019\u001A\u001B\u001C\u001D\u001E\u001F" +
+            "\u0020\u0021\u0022\u0023\u0024" +  "\u0026\u0027\u0028\u0029\u002A\u002B\u002C\u002D\u002E\u002F" +
+            "\u0030\u0031\u0032\u0033\u0034\u0035\u0036\u0037\u0038\u0039\u003A\u003B\u003C\u003D\u003E\u003F" +
+            "\u0040\u0041\u0042\u0043\u0044\u0045\u0046\u0047\u0048\u0049\u004A\u004B\u004C\u004D\u004E\u004F" +
+            "\u0050\u0051\u0052\u0053\u0054\u0055\u0056\u0057\u0058\u0059\u005A\u005B\u005C\u005D\u005E\u005F" +
+            "\u0060\u0061\u0062\u0063\u0064\u0065\u0066\u0067\u0068\u0069\u006A\u006B\u006C\u006D\u006E\u006F" +
+            "\u0070\u0071\u0072\u0073\u0074\u0075\u0076\u0077\u0078\u0079\u007A\u007B\u007C\u007D\u007E\u007F");
+
+        /// <summary>
+        /// Unescapes entire string and checks if it has unicode chars.Also checks for sequences that are 3986 Unreserved characters as these should be un-escaped
+        /// </summary>
         private static bool CheckForUnicodeOrEscapedUnreserved(string data)
         {
-            for (int i = 0; i < data.Length; i++)
+            int i = data.AsSpan().IndexOfAnyExcept(s_asciiOtherThanPercent);
+            if (i >= 0)
             {
-                char c = data[i];
-                if (c == '%')
+                for ( ; i < data.Length; i++)
                 {
-                    if ((uint)(i + 2) < (uint)data.Length)
+                    char c = data[i];
+                    if (c == '%')
                     {
-                        char value = UriHelper.DecodeHexChars(data[i + 1], data[i + 2]);
-
-                        if (!char.IsAscii(value) || UriHelper.Unreserved.Contains(value))
+                        if ((uint)(i + 2) < (uint)data.Length)
                         {
-                            return true;
-                        }
+                            char value = UriHelper.DecodeHexChars(data[i + 1], data[i + 2]);
+
+                            if (!char.IsAscii(value) || UriHelper.Unreserved.Contains(value))
+                            {
+                                return true;
+                            }
 
-                        i += 2;
+                            i += 2;
+                        }
+                    }
+                    else if (c > 0x7F)
+                    {
+                        return true;
                     }
-                }
-                else if (c > 0x7F)
-                {
-                    return true;
                 }
             }
+
             return false;
         }