Have you ever tried to determine the changes between two versions of a spreadsheet, only to be thwarted by the comparison feature in your Office Suite?  My encounters with Microsoft Office versions 95 through to 2007 certainly have had mixed results.  While Microsoft Word’s capabilities are generally OK, the comparison features in the rest of the suite (assuming one is provided at all) have not been able to meet my requirements.  Thankfully we don’t need to rely upon these any longer.

WinMerge is an Open Source application best known for its ability to compare and merge text files and directories.  What is not so well known is it can compare Office files as well. 

Basic Office Document Support (Word/Excel Only)

If you only require the ability to compare Excel or Word files:

1. Download the WinMerge installer and begin the install
2. When you reach the "Installation Type" dialog, select the Plugins entry in component list
3. When prompted ensure the "Enable Explorer context menu integration" option is selected
4. Finish the installation

If you have Microsoft Office installed on your system, you are now able to compare Excel spreadsheets or Word documents using WinMerge.  Simply select two documents in Windows Explorer, right click on them, and select the WinMerge item on the context menu.  An example of the comparison between two spreadsheets is included below.

Extended Office Document Support (Various Office Document Types and Suites)

If your Office document comparison requirements are a little more sophisticated, or you don’t have Microsoft Office installed on your system, it is fairly easy to add support for the following document types:

These capabilities are added by the freely available xdocdiff WinMerge Plugin.  To install (with thanks to the xdocdiff WinMerge Plugin homepage):

1. Follow the "Basic Office Document Support" steps above
2. Run WinMerge
3. Select the "Automatic Unpacking" option from the "Plugins" menu
4. Close WinMerge
5. Download the xdocdiff WinMerge Plugin
6. Unzip the file
7. Copy xdoc2txt.exe and zlib.dll to the WinMerge program folder. (Where WinMerge.exe is located. Default: "C:\Program Files\WinMerge")
8. Copy amb_xdocdiffPlugin.dll to the "MergePlugins" sub folder in the WinMerge program folder

The usage steps are the same as before: select two documents in Windows Explorer, right click on them, and select the WinMerge item on the context menu.  An example of the comparison between two spreadsheets is included below.  You will noticed that this plugin does not support comparison of document properties (a feature included in the builtin Excel functionality) but I believe that is a small price to pay for the additional document support.

So next time you need to compare two Office documents don’t go hunting around your Office suite’s menus - WinMerge them!