diff --git a/Cauldron.Macos/Main.storyboard b/Cauldron.Macos/Main.storyboard
index 0634e53..5eb2ba2 100644
--- a/Cauldron.Macos/Main.storyboard
+++ b/Cauldron.Macos/Main.storyboard
@@ -684,7 +684,7 @@
                             </subviews>
                         </clipView>
                         <scroller key="horizontalScroller" hidden="YES" wantsLayer="YES" verticalHuggingPriority="750" horizontal="YES" id="vhq-Zf-7BV">
-                            <rect key="frame" x="-100" y="-100" width="240" height="16"/>
+                            <rect key="frame" x="-100" y="-100" width="700" height="16"/>
                             <autoresizingMask key="autoresizingMask"/>
                         </scroller>
                         <scroller key="verticalScroller" wantsLayer="YES" verticalHuggingPriority="750" horizontal="NO" id="S8X-st-Qy9">
diff --git a/Cauldron.Macos/SourceWriter/LineNumberRuler.cs b/Cauldron.Macos/SourceWriter/LineNumberRuler.cs
new file mode 100644
index 0000000..5ed9366
--- /dev/null
+++ b/Cauldron.Macos/SourceWriter/LineNumberRuler.cs
@@ -0,0 +1,126 @@
+using System;
+using AppKit;
+using CoreGraphics;
+using Foundation;
+
+namespace Cauldron.Macos.SourceWriter;
+
+public class LineNumberRuler : NSRulerView
+{
+	private NSColor _foregroundColor = NSColor.DisabledControlText;
+	private NSColor _backgroundColor = NSColor.TextBackground;
+
+	public float GutterWidth { get; private set; } = 40f;
+	public NSColor ForegroundColor
+	{
+		get => this._foregroundColor;
+		set
+		{
+			this._foregroundColor = value;
+			this.NeedsDisplay = true;
+		}
+	}
+	public NSColor BackgroundColor
+	{
+		get => this._backgroundColor;
+		set
+		{
+			this._backgroundColor = value;
+			this.NeedsDisplay = true;
+		}
+	}
+
+	public LineNumberRuler(NSTextView textView)
+		: base(textView.EnclosingScrollView, NSRulerOrientation.Vertical)
+	{
+		this.ClientView = textView;
+		this.RuleThickness = this.GutterWidth;
+	}
+
+	public LineNumberRuler(NSTextView textView, NSColor foregroundColor, NSColor backgroundColor)
+		: base(textView.EnclosingScrollView, NSRulerOrientation.Vertical)
+	{
+		this.ClientView = textView;
+		this.ForegroundColor = foregroundColor;
+		this.BackgroundColor = backgroundColor;
+		this.RuleThickness = this.GutterWidth;
+	}
+
+	public override void DrawHashMarksAndLabels(CGRect rect)
+	{
+		this.BackgroundColor.Set();
+		NSGraphicsContext.CurrentContext.CGContext.FillRect(rect);
+
+		if (this.ClientView is not NSTextView textView)
+			return;
+
+		NSLayoutManager layoutManager = textView.LayoutManager;
+		NSTextContainer textContainer = textView.TextContainer;
+
+		if (layoutManager is null || textContainer is null)
+			return;
+
+		NSString content = new NSString(textView.Value);
+		NSRange visibleGlyphsRange = layoutManager
+			.GetGlyphRangeForBoundingRect(textView.VisibleRect(), textContainer);
+
+		int lineNumber = 1;
+
+		NSRegularExpression newlineRegex = new NSRegularExpression(new NSString("\n"),
+			new NSRegularExpressionOptions(), out NSError error);
+		if (error is not null)
+			return;
+
+		lineNumber += (int)newlineRegex.GetNumberOfMatches(content, new NSMatchingOptions(),
+			new NSRange(0, visibleGlyphsRange.Location));
+
+		nint firstGlyphOfLineIndex = visibleGlyphsRange.Location;
+
+		while (firstGlyphOfLineIndex < visibleGlyphsRange.Location + visibleGlyphsRange.Length)
+		{
+			NSRange charRangeOfLine = content.LineRangeForRange(
+				new NSRange((nint)layoutManager.GetCharacterIndex((nuint)firstGlyphOfLineIndex), 0));
+			NSRange glyphRangeOfLine = layoutManager.GetGlyphRange(charRangeOfLine);
+
+			nint firstGlyphOfRowIndex = firstGlyphOfLineIndex;
+			int lineWrapCount = 0;
+
+			while (firstGlyphOfRowIndex < glyphRangeOfLine.Location + glyphRangeOfLine.Length)
+			{
+				CGRect lineRect = layoutManager.GetLineFragmentRect((nuint)firstGlyphOfRowIndex,
+					out NSRange effectiveRange, true);
+
+				if (lineWrapCount == 0)
+					this.DrawLineNumber(lineNumber, (float)lineRect.GetMinY()
+						+ (float)textView.TextContainerInset.Height);
+				else
+					break;
+
+				// Move to next row
+				firstGlyphOfRowIndex = effectiveRange.Location + effectiveRange.Length;
+			}
+
+			firstGlyphOfLineIndex = glyphRangeOfLine.Location + glyphRangeOfLine.Length;
+			lineNumber += 1;
+		}
+
+		if (layoutManager.ExtraLineFragmentTextContainer != null)
+			this.DrawLineNumber(lineNumber, (float)layoutManager.ExtraLineFragmentRect.GetMinY()
+				+ (float)textView.TextContainerInset.Height);
+	}
+
+	private void DrawLineNumber(int lineNumber, float yPosition)
+	{
+		if (this.ClientView is not NSTextView textView)
+			return;
+
+		NSDictionary attributes = new(NSStringAttributeKey.Font, textView.Font,
+			NSStringAttributeKey.ForegroundColor, this.ForegroundColor);
+		NSAttributedString attributedLineNumber = new(lineNumber.ToString(), attributes);
+		CGPoint relativePoint = this.ConvertPointFromView(CGPoint.Empty, textView);
+		nfloat xPosition = this.GutterWidth - (attributedLineNumber.Size.Width + 8);
+
+		attributedLineNumber.DrawAtPoint(new CGPoint(xPosition, relativePoint.Y + yPosition));
+	}
+}
+
diff --git a/Cauldron.Macos/SourceWriter/SourceTextView.cs b/Cauldron.Macos/SourceWriter/SourceTextView.cs
index acfd397..3bbcb47 100644
--- a/Cauldron.Macos/SourceWriter/SourceTextView.cs
+++ b/Cauldron.Macos/SourceWriter/SourceTextView.cs
@@ -52,6 +52,8 @@ public class SourceTextView : NSTextView
 	/// <summary>Should the editor only use default words if the keyword list is empty.</summary>
 	private bool _defaultWordsOnlyIfKeywordsEmpty = true;
 
+	private LineNumberRuler LineNumberRuler;
+
 	#endregion
 
 	#region Computed Properties
@@ -245,6 +247,28 @@ public class SourceTextView : NSTextView
 		this.UsesAdaptiveColorMappingForDarkAppearance = true;
 	}
 
+	public override void AwakeFromNib()
+	{
+		base.AwakeFromNib();
+
+		this.LineNumberRuler = new LineNumberRuler(this);
+
+		this.EnclosingScrollView.VerticalRulerView = this.LineNumberRuler;
+		this.EnclosingScrollView.HasVerticalRuler = true;
+		this.EnclosingScrollView.RulersVisible = true;
+
+		this.PostsFrameChangedNotifications = true;
+		NSView.Notifications.ObserveBoundsChanged((_, _) => this.DrawGutter());
+		this.OnTextChanged += (_, _) => this.DrawGutter();
+	}
+
+	[Export("drawGutter")]
+	public void DrawGutter()
+	{
+		if (this.LineNumberRuler is not null)
+			this.LineNumberRuler.NeedsDisplay = true;
+	}
+
 	#endregion
 
 	#region Private Methods
@@ -678,6 +702,7 @@ public class SourceTextView : NSTextView
 		// Console.WriteLine ("Read selection from pasteboard");
 		bool result = base.ReadSelectionFromPasteboard(pboard);
 		Formatter?.Reformat();
+		this.OnTextChanged?.Invoke(this, null);
 		return result;
 	}
 
@@ -695,6 +720,7 @@ public class SourceTextView : NSTextView
 		// Console.WriteLine ("Read selection from pasteboard also");
 		var result = base.ReadSelectionFromPasteboard(pboard, type);
 		Formatter?.Reformat();
+		this.OnTextChanged?.Invoke(this, null);
 		return result;
 	}