diff --git a/src/Tokenizer/BaseTokenizer.cs b/src/Tokenizer/BaseTokenizer.cs
index 3d87111..b2cb163 100644
--- a/src/Tokenizer/BaseTokenizer.cs
+++ b/src/Tokenizer/BaseTokenizer.cs
@@ -109,7 +109,7 @@ public TokensWithOffsets TokenizeWithOffsets(string text)
 
         foreach (var token in tokens)
         {
-            texts.Add(token.Text);
+            texts.Add(new string(token.Text));
             offsets.Add(token.ReferenceOffsets.Any() ? new Offset(token.ReferenceOffsets.First(), token.ReferenceOffsets.Last() + 1) : (Offset?)null);
             originalPositions.Add(token.ReferenceOffsets);
             masks.Add(token.Mask);
@@ -174,7 +174,7 @@ public virtual List<Token> TokenizeToTokens(Token initialToken)
 
                 return ownedToken;
             })
-            .Where(token => !string.IsNullOrEmpty(token.Text))
+            .Where(token => !string.IsNullOrEmpty(new string(token.Text)))
             .ToList();
 
         return tokens;
@@ -183,7 +183,7 @@ public virtual List<Token> TokenizeToTokens(Token initialToken)
     public void DecomposeNfkc(Token token)
     {
         // Perform NFKC normalization on the token text
-        var decomposedText = token.Text.Normalize(NormalizationForm.FormKC);
+        var decomposedText = new string(token.Text).Normalize(NormalizationForm.FormKC);
 
         // Calculate the new reference offsets
         var newReferenceOffsets = new List<uint>();
@@ -197,7 +197,7 @@ public void DecomposeNfkc(Token token)
         }
 
         // Update the token's properties
-        token.Text = decomposedText;
+        token.Text = decomposedText.ToCharArray();
         token.ReferenceOffsets = newReferenceOffsets;
         token.Offset.Begin = newReferenceOffsets.FirstOrDefault();
         token.Offset.End = newReferenceOffsets.LastOrDefault() + 1;
@@ -357,11 +357,11 @@ private string ConvertTokensToString(List<string> tokens)
     protected List<Token> SplitOnSpecialTokens(Token token, IVocab vocab)
     {
 
-        Func<string, (int, int, Mask)> testSubstr = (s) =>
+        Func<char[], (int, int, Mask)> testSubstr = (s) =>
         {
             foreach (var specialValue in vocab.SpecialValues.Keys)
             {
-                if (s.StartsWith(specialValue))
+                if (new string(s).StartsWith(specialValue))
                 {
                     return (
                         specialValue.Length,
@@ -400,7 +400,7 @@ private string CleanUpTokenization(string inputString)
 
     private List<Token> WhitespaceTokenize(Token initialToken)
     {
-        var parts = initialToken.Text.Split(new[] { ' ', '\t', '\n', '\r' }, StringSplitOptions.RemoveEmptyEntries);
+        var parts = new string(initialToken.Text).Split(new[] { ' ', '\t', '\n', '\r' }, StringSplitOptions.RemoveEmptyEntries);
         var tokens = new List<Token>();
         foreach (var part in parts)
         {
@@ -410,7 +410,7 @@ private List<Token> WhitespaceTokenize(Token initialToken)
         return tokens;
     }
 
-    private List<Token> SplitOnSubstr(Token token, Func<string, (int, int, Mask)> testSubstr, bool addSeparators)
+    private List<Token> SplitOnSubstr(Token token, Func<char[], (int, int, Mask)> testSubstr, bool addSeparators)
     {
         var tokens = new List<Token>();
         uint charBegin = 0;
@@ -420,7 +420,7 @@ private List<Token> SplitOnSubstr(Token token, Func<string, (int, int, Mask)> te
         if (token.Mask == Mask.None)
         {
             // Iterate over characters with byte indices
-            var itr = TokenizationUtils.Enumerate(TokenizationUtils.CharIndicesForRunes(token.Text));
+            var itr = TokenizationUtils.Enumerate(TokenizationUtils.CharIndicesForRunes(new string(token.Text)));
             foreach (var (charIdx, (bytesIdx, _)) in itr)
             {
                 charCount++;
@@ -431,7 +431,7 @@ private List<Token> SplitOnSubstr(Token token, Func<string, (int, int, Mask)> te
                     if (charBegin < charIdx)
                     {
                         // Add previous token
-                        var trimmedText = TokenizationUtils.SubstringRunes(token.Text, bytesBegin, bytesIdx - bytesBegin).TrimEnd();
+                        var trimmedText = new string(TokenizationUtils.SubstringRunes(token.Text, bytesBegin, bytesIdx - bytesBegin)).TrimEnd();
                         if (trimmedText.EnumerateRunes().Count() > 0)
                         {
                             tokens.Add(new Token(trimmedText)
@@ -468,7 +468,7 @@ private List<Token> SplitOnSubstr(Token token, Func<string, (int, int, Mask)> te
             var text = TokenizationUtils.SubstringRunes(token.Text, bytesBegin, bytesBegin + (bytesIdx - bytesBegin));
             if (charCount == 0)
             {
-                charCount = token.Text.EnumerateRunes().Count();
+                charCount = new string(token.Text).EnumerateRunes().Count();
             }
             tokens.Add(new Token(text)
             {
@@ -493,7 +493,7 @@ private List<Token> SplitOnPunct(Token token)
             if (char.IsPunctuation(charCurrent))
             {
                 var offsets = token.ReferenceOffsets.Skip(start).Take(1).ToArray();
-                tokens.Add(new Token(text.Substring(start, 1), offsets) { Mask = Mask.Punctuation });
+                tokens.Add(new Token(new string(text).Substring(start, 1), offsets) { Mask = Mask.Punctuation });
                 start++;
             }
             else
@@ -504,7 +504,7 @@ private List<Token> SplitOnPunct(Token token)
                     end++;
                 }
                 var offsets = token.ReferenceOffsets.Skip(start).Take(end - start).ToArray();
-                tokens.Add(new Token(text.Substring(start, end - start), offsets));
+                tokens.Add(new Token(new string(text).Substring(start, end - start), offsets));
                 start = end;
             }
         }
@@ -523,7 +523,7 @@ private List<Token> TokenizeCjkChars(Token token)
             if (IsCjkChar(charCurrent))
             {
                 var offsets = token.ReferenceOffsets.Skip(start).Take(1).ToArray();
-                tokens.Add(new Token(text.Substring(start, 1), offsets) { Mask = Mask.CJK });
+                tokens.Add(new Token(new string(text).Substring(start, 1), offsets) { Mask = Mask.CJK });
                 start++;
             }
             else
@@ -534,7 +534,7 @@ private List<Token> TokenizeCjkChars(Token token)
                     end++;
                 }
                 var offsets = token.ReferenceOffsets.Skip(start).Take(end - start).ToArray();
-                tokens.Add(new Token(text.Substring(start, end - start), offsets));
+                tokens.Add(new Token(new string(text).Substring(start, end - start), offsets));
                 start = end;
             }
         }
@@ -551,19 +551,19 @@ private void CleanText(Token token, bool removeControlCharacters)
     {
         if (removeControlCharacters)
         {
-            token.Text = Regex.Replace(token.Text, @"\p{C}+", "");
+            token.Text = Regex.Replace(new string(token.Text), @"\p{C}+", "").ToCharArray();
         }
-        token.Text = token.Text.Replace("``", "\"").Replace("''", "\"");
+        token.Text = new string(token.Text).Replace("``", "\"").Replace("''", "\"").ToCharArray();
     }
     
     private void Lowercase(Token token)
     {
-        token.Text = token.Text.ToLowerInvariant();
+        token.Text = new string(token.Text).ToLowerInvariant().ToCharArray();
     }
 
     private void StripAccents(Token token)
     {
-        token.Text = RemoveDiacritics(token.Text);
+        token.Text = RemoveDiacritics(new string(token.Text)).ToCharArray();
     }
 
     private string RemoveDiacritics(string text)
diff --git a/src/Tokenizer/Token.cs b/src/Tokenizer/Token.cs
index 09c6682..b031d64 100644
--- a/src/Tokenizer/Token.cs
+++ b/src/Tokenizer/Token.cs
@@ -8,7 +8,7 @@ public class Token : IToken
     /// <summary>
     /// String representation
     /// </summary>
-    public string Text { get; set; }
+    public char[] Text { get; set; }
 
     /// <summary>
     /// Start and end positions of the token with respect to the original text
@@ -30,9 +30,9 @@ public class Token : IToken
     /// Creates a new owned token from a `String`.
     /// </summary>
     /// <param name="text">text reference</param>
-    public Token(string text)
+    public Token(ReadOnlySpan<char> text)
     {
-        Text = text;
+        Text = text.ToArray();
         var text_size = (uint)text.Length;
         Offset = new Offset(0, text_size);
         ReferenceOffsets = Enumerable.Range(0, (int)text_size).Select(i => (uint)i).ToList();
@@ -44,17 +44,17 @@ public Token(string text)
     /// </summary>
     /// <param name="text">text reference</param>
     /// <param name="offsets">reference positions with respect to the original text</param>
-    public Token(string text, uint[] offsets)
+    public Token(ReadOnlySpan<char> text, uint[] offsets)
     {
-        Text = text;
+        Text = text.ToArray();
         Offset = new Offset(0, (uint)offsets.Length);
         ReferenceOffsets = offsets;
         Mask = Mask.None;
     }
 
-    public Token(string text, Offset offset, IReadOnlyList<uint> referenceOffsets, Mask mask)
+    public Token(ReadOnlySpan<char> text, Offset offset, IReadOnlyList<uint> referenceOffsets, Mask mask)
     {
-        Text = text;
+        Text = text.ToArray();
         Offset = offset;
         ReferenceOffsets = referenceOffsets;
         Mask = mask;
@@ -62,7 +62,7 @@ public Token(string text, Offset offset, IReadOnlyList<uint> referenceOffsets, M
 
     public override string ToString()
     {
-        return Text;
+        return new string(Text);
     }
 
     public static Token From(string text)
diff --git a/src/Tokenizer/TokenizationUtils.cs b/src/Tokenizer/TokenizationUtils.cs
index 2d3f04e..25de862 100644
--- a/src/Tokenizer/TokenizationUtils.cs
+++ b/src/Tokenizer/TokenizationUtils.cs
@@ -11,38 +11,31 @@ namespace Lokad.Tokenizers.Tokenizer;
 
 internal static class TokenizationUtils
 {
+
     /// <summary>
     /// Substring Runes (characters)
     /// </summary>
-    public static string SubstringRunes(string text, int start, int length)
+    public static char[] SubstringRunes(ReadOnlySpan<char> text, int start, int length)
     {
         var sb = new StringBuilder();
-        text.EnumerateRunes().Skip(start).Take(length).ToList().ForEach(r => sb.Append(r));
-        return sb.ToString();
+        text.EnumerateRunes().ToList().Skip(start).Take(length).ToList().ForEach(r => sb.Append(r));
+        return sb.ToString().ToCharArray();
     }
 
     /// <summary>
     /// Substring Runes (characters)
     /// </summary>
-    public static string SubstringRunes(string text, int start)
+    public static char[] SubstringRunes(ReadOnlySpan<char> text, int start)
     {
         var sb = new StringBuilder();
-        text.EnumerateRunes().Skip(start).ToList().ForEach(r => sb.Append(r));
-        return sb.ToString();
-    }
-
-    /// <summary>
-    /// Get String Info
-    /// </summary>
-    public static StringInfo GetStringInfo(string text)
-    {
-        return new System.Globalization.StringInfo(text);
+        text.EnumerateRunes().ToList().Skip(start).ToList().ForEach(r => sb.Append(r));
+        return sb.ToString().ToCharArray();
     }
 
     /// <summary>
     /// Get UTF 8 Bytes Count
     /// </summary>
-    public static int GetUtf8BytesCount(string text)
+    public static int GetUtf8BytesCount(ReadOnlySpan<char> text)
     {
         return Encoding.UTF8.GetByteCount(text);
     }
@@ -66,7 +59,7 @@ public static int GetUtf8BytesCount(string text)
     /// NFKC decomposition
     /// </summary>
     public static IEnumerable<(Rune Character, int ExtraCharSize)> NFKC(string str)
-    {
+            {
         var runes = str.EnumerateRunes().ToList();
         for (var i = 0; i < runes.Count; i++)
         {
@@ -89,18 +82,18 @@ public static int GetUtf8BytesCount(string text)
     /// <summary>
     /// Substring by byte offset
     /// </summary>
-    public static string SubstringByByteOffset(string s, int start)
+    public static char[] SubstringByByteOffset(char[] s, int start)
     {
         var bytes = Encoding.UTF8.GetBytes(s);
         var substringBytes = new byte[bytes.Length - start];
         Array.Copy(bytes, start, substringBytes, 0, bytes.Length - start);
-        return Encoding.UTF8.GetString(substringBytes);
+        return Encoding.UTF8.GetChars(substringBytes);
     }
 
     /// <summary>
     /// Substring by byte offset
     /// </summary>
-    public static string SubstringByByteOffset(string s, int start, int end)
+    public static char[] SubstringByByteOffset(char[] s, int start, int end)
     {
         var bytes = Encoding.UTF8.GetBytes(s);
         if (end > bytes.Length || start > end)
@@ -109,7 +102,7 @@ public static string SubstringByByteOffset(string s, int start, int end)
         }
         var substringBytes = new byte[end - start];
         Array.Copy(bytes, start, substringBytes, 0, end - start);
-        return Encoding.UTF8.GetString(substringBytes);
+        return Encoding.UTF8.GetChars(substringBytes);
     }
 
     /// <summary>
@@ -120,7 +113,7 @@ public static void CleanText(Token token, bool strict)
         var cleanedString = new StringBuilder(token.Text.Length);
         var characterMapping = new List<uint>(token.Text.Length);
 
-        foreach (var (character, position) in token.Text.EnumerateRunes().Zip(token.ReferenceOffsets))
+        foreach (var (character, position) in token.Text.AsSpan().EnumerateRunes().ToList().Zip(token.ReferenceOffsets))
         {
             if (IsControl(character, strict) || character == new Rune('\x00') || character == new Rune('\uFFFD'))
             {
@@ -131,7 +124,7 @@ public static void CleanText(Token token, bool strict)
             characterMapping.Add(position);
         }
 
-        token.Text = cleanedString.ToString();
+        token.Text = cleanedString.ToString().ToCharArray();
         token.ReferenceOffsets = characterMapping;
         token.Offset = new Offset(token.ReferenceOffsets.FirstOrDefault(), token.ReferenceOffsets.LastOrDefault() + 1);
     }
@@ -191,7 +184,7 @@ public static void Lowercase(Token token)
             }
         }
 
-        token.Text = lowerCasedString.ToString();
+        token.Text = lowerCasedString.ToString().ToCharArray();
         token.ReferenceOffsets = characterMapping;
         token.Offset = new Offset(token.ReferenceOffsets.FirstOrDefault(), token.ReferenceOffsets.LastOrDefault() + 1);
     }
@@ -205,13 +198,13 @@ public static void DecomposeNfkc(Token token)
         var decomposedString = new StringBuilder(capacity);
         var characterMapping = new List<uint>(capacity);
         var curPosition = 0;
-        var normalizedString = token.Text.Normalize(NormalizationForm.FormKC);
+        var normalizedString = new string(token.Text).Normalize(NormalizationForm.FormKC);
         foreach (var (character, currentExtraCharSize) in TokenizationUtils.NFKC(normalizedString))
         {
             var extraCharSize = 0;
 
             //HINT: [@eslam] check if character is removed from the original text after normalization
-            if (!token.Text.EnumerateRunes().Contains(character))
+            if (!token.Text.AsSpan().EnumerateRunes().ToList().Contains(character))
                 extraCharSize -= currentExtraCharSize;
 
             decomposedString.Append(character);
@@ -236,7 +229,7 @@ public static void DecomposeNfkc(Token token)
             curPosition += 1; // Adjust based on Unicode character width if needed
         }
 
-        token.Text = decomposedString.ToString();//.Normalize(NormalizationForm.FormKC);
+        token.Text = decomposedString.ToString().ToCharArray();//.Normalize(NormalizationForm.FormKC);
         token.ReferenceOffsets = characterMapping;
         token.Offset.Begin = token.ReferenceOffsets.FirstOrDefault();
         token.Offset.End = token.ReferenceOffsets.LastOrDefault() + 1;
@@ -475,4 +468,17 @@ public static (TokenIdsWithOffsets, TokenIdsWithOffsets?, List<long>, List<Offse
         }
     }
 
+    /// <summary>
+    /// extension method to enumerate span runes to list
+    /// </summary>
+    public static List<Rune> ToList(this SpanRuneEnumerator enumerator)
+    {
+        var runes = new List<Rune>();
+        foreach (var rune in enumerator)
+        {
+            runes.Add(rune);
+        }
+        return runes;
+    }
+
 }
\ No newline at end of file
diff --git a/src/Tokenizer/XLMRobertaTokenizer.cs b/src/Tokenizer/XLMRobertaTokenizer.cs
index ccaf379..10b7b24 100644
--- a/src/Tokenizer/XLMRobertaTokenizer.cs
+++ b/src/Tokenizer/XLMRobertaTokenizer.cs
@@ -75,15 +75,15 @@ public override List<Token> TokenizeToTokens(Token tokenRef)
 
                 // Manually replacing whitespace characters
                 var newText = new StringBuilder();
-                foreach (var c in token.Text.EnumerateRunes())
+                foreach (var c in token.Text.AsSpan().EnumerateRunes().ToList())
                 {
                     newText.Append(TokenizationUtils.IsWhitespace(c) ? new Rune(Constants.LowerOneEighthBlock) : c.ToString());
                 }
-                token.Text = newText.ToString();
+                token.Text = newText.ToString().ToCharArray();
 
-                if (!token.Text.StartsWith(Constants.LowerOneEighthBlock))
+                if (!new string(token.Text).StartsWith(Constants.LowerOneEighthBlock))
                 {
-                    token.Text = Constants.LowerOneEighthBlock + token.Text;
+                    token.Text = (Constants.LowerOneEighthBlock.ToString() + new string(token.Text)).ToCharArray();
                     var newReferenceOffsets = new List<uint> { 0 };
                     newReferenceOffsets.AddRange(token.ReferenceOffsets);
                     token.ReferenceOffsets = newReferenceOffsets;
diff --git a/src/Vocab/SentencePieceUnigramModel.cs b/src/Vocab/SentencePieceUnigramModel.cs
index 8423ec5..d49d2ee 100644
--- a/src/Vocab/SentencePieceUnigramModel.cs
+++ b/src/Vocab/SentencePieceUnigramModel.cs
@@ -125,7 +125,7 @@ public List<TrieNode> CommonPrefixSearch(string text)
     {
         var charPositions = new List<int>();
 
-        var runes = TokenizationUtils.CharIndicesForRunes(token.Text).ToList();
+        var runes = TokenizationUtils.CharIndicesForRunes(new string(token.Text)).ToList();
         runes.ForEach((i => charPositions.Add(i.Index)));
         charPositions.Add(TokenizationUtils.GetUtf8BytesCount(token.Text));
 
@@ -136,7 +136,7 @@ public List<TrieNode> CommonPrefixSearch(string text)
         for (var charStart = 0; charStart < charPositions.Count - 1; charStart++)
         {
             var prefix = TokenizationUtils.SubstringByByteOffset(token.Text, charPositions[charStart]);
-            var matches = CommonPrefixSearch(prefix.ToString());
+            var matches = CommonPrefixSearch(new string(prefix));
 
             foreach (var node in matches)
             {
@@ -148,7 +148,7 @@ public List<TrieNode> CommonPrefixSearch(string text)
                     var t = TokenizationUtils.SubstringByByteOffset(token.Text, charPositions[charStart], charPositions[charEnd]);
                     results[charEnd] = new Node
                     (
-                        text: t,
+                        text: new string(t),
                         score: localScore,
                         index: node.Index,
                         start: charStart,
@@ -165,7 +165,7 @@ public List<TrieNode> CommonPrefixSearch(string text)
                 var t = TokenizationUtils.SubstringByByteOffset(token.Text, charPositions[charStart], charPositions[charStart + 1]);
                 results[charStart + 1] = new Node
                 (
-                    text: t,
+                    text: new string(t),
                     score: float.MinValue,
                     index: 0,
                     start: charStart,
@@ -217,13 +217,13 @@ public List<Token> ParseNodesToTokens(List<Node> nodes)
             if (isPrevUnknown && (node.Index == 0))
             {
                 var prevToken = output.Last();
-                var text = new StringBuilder(prevToken.Text);
+                var text = new StringBuilder(new string(prevToken.Text));
                 text.Append(node.Text);
                 var referenceOffsets = new List<uint>();
                 referenceOffsets.AddRange(node.ReferenceOffsets);
                 var consolidatedUnknown = new Token(text.ToString())
                 {
-                    Text = text.ToString(),
+                    Text = text.ToString().ToCharArray(),
                     Offset = new Offset(0, 0),
                     ReferenceOffsets = referenceOffsets,
                     Mask = Mask.Unknown,
@@ -235,7 +235,7 @@ public List<Token> ParseNodesToTokens(List<Node> nodes)
             {
                 output.Add(new Token(node.Text)
                 {
-                    Text = node.Text,
+                    Text = node.Text.ToCharArray(),
                     Offset = new Offset(0, 0),
                     ReferenceOffsets = node.ReferenceOffsets.ToList(),
                     Mask = Mask.None,
@@ -278,7 +278,7 @@ public void PopulateMasks(List<Token> tokens, char whitespaceToken)
                 }
             }
 
-            if (!token.Text.StartsWith(whitespaceToken) && previousMask != Mask.Punctuation && previousMask != Mask.Whitespace)
+            if (!new string(token.Text).StartsWith(whitespaceToken) && previousMask != Mask.Punctuation && previousMask != Mask.Whitespace)
             {
                 token.Mask = Mask.Continuation;
                 previousMask = Mask.Continuation;
diff --git a/test/Tokenizer/TokenizationUtilsTests.cs b/test/Tokenizer/TokenizationUtilsTests.cs
index 7d2274c..183e9b0 100644
--- a/test/Tokenizer/TokenizationUtilsTests.cs
+++ b/test/Tokenizer/TokenizationUtilsTests.cs
@@ -135,10 +135,10 @@ public void TestSubString_01()
         var s = "▁tokénized";
 
 
-        var prefix = TokenizationUtils.SubstringByByteOffset(s, 0);
+        var prefix = TokenizationUtils.SubstringByByteOffset(s.ToCharArray(), 0);
 
         // Expected positions
-        var expected = "▁tokénized";
+        var expected = "▁tokénized".ToCharArray();
         // Assert that the character positions match the expected positions
         Assert.Equal(expected, prefix);
     }
@@ -149,10 +149,10 @@ public void TestSubString_02()
         var s = "▁tokénized";
 
 
-        var prefix = TokenizationUtils.SubstringByByteOffset(s, 3);
+        var prefix = TokenizationUtils.SubstringByByteOffset(s.ToCharArray(), 3);
 
         // Expected positions
-        var expected = "tokénized";
+        var expected = "tokénized".ToCharArray();
         // Assert that the character positions match the expected positions
         Assert.Equal(expected, prefix);
     }