A .NET tool that compares two Word documents side by side using Microsoft Word's built-in document comparison feature.

• MsWordDiff (diffword) — Compare two Word documents using Microsoft Word's built-in document comparison feature
• MsExcelDiff (diffexcel) — Compare two Excel workbooks using Microsoft's Spreadsheet Compare

See Milestones for release notes.

Requirements

• Windows
• .NET 10.0 or later

MsWordDiff

Requires Microsoft Word installed (for MsWordDiff)

Installation

dotnet tool install -g MsWordDiff

Nuget: https://nuget.org/packages/MsWordDiff/

Usage

diffword <path1> <path2> [--quiet]

Where <path1> and <path2> are paths to the Word documents to compare.

Example:

diffword original.docx modified.docx

This will open Microsoft Word with a comparison view showing the differences between the two documents. The tool will wait until Word is closed before exiting.

Options

--quiet

Hide source documents in the comparison view, showing only the comparison document.

Example:

diffword original.docx modified.docx --quiet

Showing Original and Revised Panes in Quiet Mode

When using --quiet mode, the original and revised document panes are initially hidden. They can be shown at any time within Word:

1. Click the Review tab in Word's ribbon
2. In the Compare group, click Compare
3. Select Show Source Documents
4. Choose the preferred view:
   • Show Both - Displays both original and revised documents in the right pane
   • Show Original - Shows only the original document
   • Show Revised - Shows only the revised document
   • Hide Source Documents - Returns to quiet mode (comparison only)

When both documents are visible, they scroll in sync with the comparison document for side-by-side review.

Learn more:

• Compare and merge two versions of a document - Microsoft Support
• How to Compare Two Microsoft Word Documents

On first execution

On first execution the user will be prompted to choose their preferred UX mode (Standard or Quiet).

Configuration

The default behavior of options can be configured using settings commands.

View settings

diffword settings

This displays the settings file path and current settings.

C:\Users\SimonCropp\.config\MsWordDiff\settings.json
{
  "Quiet": true
}

By default, settings are stored in:

%USERPROFILE%\.config\MsWordDiff\settings.json

Configure default Quiet mode

diffword set-quiet <true|false>

Set the default value for the Quiet option. When set to true, the source documents will be hidden by default.

Examples:

diffword set-quiet true
diffword set-quiet false

Note: Command-line options always override settings file values.

DiffEngine Integration

MsWordDiff is supported by DiffEngine, making it available as a diff tool for Verify snapshot testing.

When using Verify to test Word document output, DiffEngine can launch MsWordDiff to show differences between expected and actual documents.

To prioritize MsWordDiff as the diff tool:

DiffTools.UseOrder(DiffTool.MsWordDiff);

See DiffEngine Diff Tool documentation for more details.

How It Works

The tool uses COM automation to:

1. Open both documents in Microsoft Word (read-only)
2. Generate a comparison document using Word's CompareDocuments feature
3. Display the comparison with tracked changes highlighting differences
4. Automatically close Word when the parent process exits

MsExcelDiff

Requires Microsoft Office Professional Plus / Microsoft 365 Apps for Enterprise as Spreadsheet Compare is only included in these editions

Installation

dotnet tool install -g MsExcelDiff

Nuget: https://nuget.org/packages/MsExcelDiff/

Usage

diffexcel <path1> <path2>

Where <path1> and <path2> are paths to the Excel workbooks to compare.

Example:

diffexcel original.xlsx modified.xlsx

This will open Microsoft Spreadsheet Compare showing the differences between the two workbooks. The tool will wait until Spreadsheet Compare is closed before exiting.

Spreadsheet Compare Availability

Spreadsheet Compare is only included with certain Office editions:

• Microsoft 365 Apps for Enterprise (formerly Office 365 ProPlus)
• Office Professional Plus (2013, 2016, 2019, 2021, 2024)

It is not included with:

• Microsoft 365 Personal or Family
• Office Home & Student
• Office Home & Business
• Office Standard

Configuration

View settings

diffexcel settings

This displays the settings file path and current settings.

By default, settings are stored in:

%USERPROFILE%\.config\MsExcelDiff\settings.json

Configure Spreadsheet Compare path

If Spreadsheet Compare is installed in a non-standard location, set the path:

diffexcel set-path "C:\Custom\Path\SPREADSHEETCOMPARE.EXE"

To clear the override and revert to auto-detection:

diffexcel set-path ""

How It Works

The tool:

1. Writes both file paths to a temp file (one per line)
2. Launches SPREADSHEETCOMPARE.EXE with the temp file as an argument
3. For Click-to-Run Office installs, launches via AppVLP.exe (the App-V virtualization layer)
4. Creates a Windows Job Object to terminate Spreadsheet Compare when the parent process exits
5. Waits until Spreadsheet Compare is closed before exiting