diff --git a/src/SmartFormat.Tests/Core/Output/CustomOutputTests.cs b/src/SmartFormat.Tests/Core/Output/CustomOutputTests.cs
new file mode 100644
index 00000000..36c406f8
--- /dev/null
+++ b/src/SmartFormat.Tests/Core/Output/CustomOutputTests.cs
@@ -0,0 +1,53 @@
+using System;
+using System.Globalization;
+using System.Text;
+using NUnit.Framework;
+using SmartFormat.Core.Extensions;
+using SmartFormat.Core.Formatting;
+using SmartFormat.Core.Output;
+using SmartFormat.ZString;
+
+namespace SmartFormat.Tests.Core.Output;
+
+internal class CustomOutput : IOutput
+{
+    private readonly StringBuilder _sb = new(1000);
+    private const string OutputFormat = "Format: {0}, Selector {1}, Formatted: {2}";
+
+    public override string ToString()
+    {
+        return _sb.ToString();
+    }
+
+    public void Write(string text, IFormattingInfo? formattingInfo = null)
+    {
+        Write(text.AsSpan(), formattingInfo);
+    }
+
+    public void Write(ReadOnlySpan<char> text, IFormattingInfo? formattingInfo = null)
+    {
+        var fi = (FormattingInfo) formattingInfo!;
+        _sb.AppendFormat(OutputFormat, fi.Format, fi.Selector, text.ToString());
+    }
+
+    public void Write(ZStringBuilder stringBuilder, IFormattingInfo? formattingInfo = null)
+    {
+        Write(stringBuilder.AsSpan(), formattingInfo);
+    }
+}
+
+[TestFixture]
+internal class CustomOutputTests
+{
+    [Test]
+    public void CustomOutput_GetsValid_FormattingInfo_Argument()
+    {
+        // This test ensures that the IOutput.Write method overloads
+        // get a valid IFormattingInfo argument.
+        var smart = Smart.CreateDefaultSmartFormat();
+        var output = new CustomOutput();
+        smart.FormatInto(output, CultureInfo.InvariantCulture, "{0:0.0000}", [9m]);
+        Assert.That(output.ToString(),
+            Is.EqualTo("Format: 0.0000, Selector 0, Formatted: 9.0000"));
+    }
+}
diff --git a/src/SmartFormat.Tests/Core/Output/StringOutputTests.cs b/src/SmartFormat.Tests/Core/Output/StringOutputTests.cs
index baa15719..7a2c7bdc 100644
--- a/src/SmartFormat.Tests/Core/Output/StringOutputTests.cs
+++ b/src/SmartFormat.Tests/Core/Output/StringOutputTests.cs
@@ -12,7 +12,7 @@ public class StringOutputTests
     public void Output_Of_Span()
     {
         var so = new StringOutput();
-        so.Write("text".AsSpan(), null!);
+        so.Write("text".AsSpan(), null);
         Assert.That(so.ToString(), Is.EqualTo("text"));
     }
 
@@ -20,7 +20,7 @@ public void Output_Of_Span()
     public void Output_Of_String()
     {
         var so = new StringOutput(16);
-        so.Write("text", null!);
+        so.Write("text", null);
         Assert.That(so.ToString(), Is.EqualTo("text"));
     }
 
@@ -30,7 +30,7 @@ public void Output_Of_ValueStringBuilder()
         var so = new StringOutput();
         using var sb = ZStringBuilderUtilities.CreateZStringBuilder();
         sb.Append("text");
-        so.Write(sb, null!);
+        so.Write(sb, null);
         Assert.That(so.ToString(), Is.EqualTo("text"));
     }
 }
diff --git a/src/SmartFormat/Core/Formatting/FormattingInfo.cs b/src/SmartFormat/Core/Formatting/FormattingInfo.cs
index 4eafd42a..ae22a4d1 100644
--- a/src/SmartFormat/Core/Formatting/FormattingInfo.cs
+++ b/src/SmartFormat/Core/Formatting/FormattingInfo.cs
@@ -173,7 +173,7 @@ public void Write(ReadOnlySpan<char> text)
     {
         if (Alignment == 0)
         {
-            FormatDetails.Output.Write(text);
+            FormatDetails.Output.Write(text, this);
             FormatDetails.Formatter.Evaluator.OnOutputWritten?.Invoke(this,
                 new Evaluator.OutputWrittenEventArgs(text.ToString()));
             return;
@@ -199,7 +199,7 @@ public void Write(ReadOnlySpan<char> text)
         }
 
         // Write the aligned text to the output
-        FormatDetails.Output.Write(buffer.GetSpan());
+        FormatDetails.Output.Write(buffer.GetSpan(), this);
 
         FormatDetails.Formatter.Evaluator.OnOutputWritten?.Invoke(this,
             new Evaluator.OutputWrittenEventArgs(buffer.ToString()));
diff --git a/src/SmartFormat/Core/Output/IOutput.cs b/src/SmartFormat/Core/Output/IOutput.cs
index 3766a150..bfdff630 100644
--- a/src/SmartFormat/Core/Output/IOutput.cs
+++ b/src/SmartFormat/Core/Output/IOutput.cs
@@ -16,8 +16,13 @@ public interface IOutput
     /// <summary>
     /// Writes a string to the output.
     /// </summary>
+    /// <remarks>
+    /// <b>Only implement a call</b> to <see cref="Write(ReadOnlySpan{char}, IFormattingInfo?)"/>
+    /// using <see cref="MemoryExtensions.AsSpan(string)"/> for '<see paramref="text"/>'.
+    /// </remarks>
     /// <param name="text"></param>
     /// <param name="formattingInfo"></param>
+    [Obsolete("Use Write(ReadOnlySpan<char> text, IFormattingInfo? formattingInfo = null) instead.", false)]
     void Write(string text, IFormattingInfo? formattingInfo = null);
 
     /// <summary>
@@ -25,12 +30,18 @@ public interface IOutput
     /// </summary>
     /// <param name="text"></param>
     /// <param name="formattingInfo"></param>
+    // v4: Remove formattingInfo argument? Or make it non-optional and non-nullable?
     void Write(ReadOnlySpan<char> text, IFormattingInfo? formattingInfo = null);
 
     /// <summary>
     /// Writes text of a <see cref="ZStringBuilder"/> to the output.
     /// </summary>
+    /// <remarks>
+    /// <b>Only implement a call</b> to <see cref="Write(ReadOnlySpan{char}, IFormattingInfo?)"/>
+    /// using <see cref="ZStringBuilder.AsSpan()"/> for '<see paramref="stringBuilder"/>'.
+    /// </remarks>
     /// <param name="stringBuilder"></param>
     /// <param name="formattingInfo"></param>
+    [Obsolete("Use Write(ReadOnlySpan<char> text, IFormattingInfo? formattingInfo = null) instead.", false)]
     void Write(ZStringBuilder stringBuilder, IFormattingInfo? formattingInfo = null);
-}
\ No newline at end of file
+}
diff --git a/src/SmartFormat/Core/Output/StringOutput.cs b/src/SmartFormat/Core/Output/StringOutput.cs
index 9f5371c2..0b9ebd78 100644
--- a/src/SmartFormat/Core/Output/StringOutput.cs
+++ b/src/SmartFormat/Core/Output/StringOutput.cs
@@ -57,7 +57,7 @@ public StringOutput(StringBuilder output)
     /// <param name="formattingInfo">This parameter from <see cref="IOutput"/> will not be used here.</param>
     public void Write(string text, IFormattingInfo? formattingInfo = null)
     {
-        Output.Append(text);
+        Write(text.AsSpan(), formattingInfo);
     }
 
     /// <summary>
@@ -77,11 +77,7 @@ public void Write(ReadOnlySpan<char> text, IFormattingInfo? formattingInfo = nul
     ///<inheritdoc/>
     public void Write(ZStringBuilder stringBuilder, IFormattingInfo? formattingInfo = null)
     {
-#if NETSTANDARD2_1 || NET6_0_OR_GREATER
-        Output.Append(stringBuilder.AsSpan());
-#else
-        Output.Append(stringBuilder);
-#endif
+        Write(stringBuilder.AsSpan(), formattingInfo);
     }
 
     /// <summary>
diff --git a/src/SmartFormat/Core/Output/TextWriterOutput.cs b/src/SmartFormat/Core/Output/TextWriterOutput.cs
index 582dbbae..d51bb7b6 100644
--- a/src/SmartFormat/Core/Output/TextWriterOutput.cs
+++ b/src/SmartFormat/Core/Output/TextWriterOutput.cs
@@ -31,7 +31,7 @@ public TextWriterOutput(TextWriter output)
     ///<inheritdoc/>
     public void Write(string text, IFormattingInfo? formattingInfo = null)
     {
-        Output.Write(text);
+        Write(text.AsSpan(), formattingInfo);
     }
 
     ///<inheritdoc/>
@@ -47,10 +47,6 @@ public void Write(ReadOnlySpan<char> text, IFormattingInfo? formattingInfo = nul
     ///<inheritdoc/>
     public void Write(ZStringBuilder stringBuilder, IFormattingInfo? formattingInfo = null)
     {
-#if NETSTANDARD2_1 || NET6_0_OR_GREATER
-        Output.Write(stringBuilder.AsSpan());
-#else
-        Output.Write(stringBuilder.ToString());
-#endif
+        Write(stringBuilder.AsSpan(), formattingInfo);
     }
 }
diff --git a/src/SmartFormat/Core/Output/ZStringOutput.cs b/src/SmartFormat/Core/Output/ZStringOutput.cs
index ffecf586..48d57180 100644
--- a/src/SmartFormat/Core/Output/ZStringOutput.cs
+++ b/src/SmartFormat/Core/Output/ZStringOutput.cs
@@ -60,7 +60,7 @@ public ZStringOutput(ZStringBuilder stringBuilder)
     ///<inheritdoc/>
     public void Write(string text, IFormattingInfo? formattingInfo = null)
     {
-        Output.Append(text);
+        Write(text.AsSpan(), formattingInfo);
     }
 
     ///<inheritdoc/>
@@ -72,7 +72,7 @@ public void Write(ReadOnlySpan<char> text, IFormattingInfo? formattingInfo = nul
     ///<inheritdoc/>
     public void Write(ZStringBuilder stringBuilder, IFormattingInfo? formattingInfo = null)
     {
-        Output.Append(stringBuilder);
+        Write(stringBuilder.AsSpan(), formattingInfo);
     }
 
     /// <summary>