WinMerge plugins are custom dlls or scriptlets, written in the COM API, that preprocess data before a comparison. For example, you can use a plugin to extract text data from MS Word files for WinMerge to compare.

Plugins are not included by default when you install WinMerge, you have to select them during installation to get them installed. This is because some plugins can give unexpected behaviour if you forget that you have the plugins turned on. These few plugins may only be of interest to a few users.

Each plugin is:

1. Plugin Types

Plugins are grouped into three main categories:

Editor complement

This type of plugin performs custom operations on selected text in the active editor (File pane) of the File Compare window.

Unpacker: transform a file to a text format

This type of plugin transforms a compressed file to a viewable format by decompressing it. The original file is not changed: a temporary transformed file is created and loaded in WinMerge.

Unpacker plugins operate on entire files, not to selected text or diffs within files. Therefore, they are available only when you launch file comparisons, from either the Folder Compare window or the Select Files or Folders dialog. Unpacker plugins are not available in the File Compare window.

Sometimes the unpacked file can be repacked (see the details in Available plugins to check whether a plugin supports repacking). Then, you can merge and save the transformed file. The packing is done automatically in this case. To be safe, we suggest that you rename the transformed file when you save it.

[Note] Note

When you compare folders, WinMerge can give different results for compressed and uncompressed files. For example, files that are identical when uncompressed might be different if they include the creation date. WinMerge applies the unpacker in all situations, and you are sure to have the same result when you compare a folder, or when you merge two versions of a file.

Example plugin: DisplayXMLFiles.dll reformats XML files for readability.

Prediffer: preprocess files to hide some differences

This type of plugin does not operate on the source files displayed in the Compare window. It operates instead on temporary copies of the files, and the copies are then scanned to create the difference list.

Example plugin: IgnoreColumns.dll ignores the differences inside specified columns, while displaying the characters in these columns.

2. Suggested plugins and automatic modes

How is WinMerge able to apply the right plugin for a given file? Each plugin specifies a list of file extensions (also listed in each plugin's Available plugins section, under File filter). The extensions are used to associate one or more file types with the plugin: when a compared file's extension matches an extension in the plugin's list, the plugin is considered to be a suggested plugin.

There are separate WinMerge options for the unpacking and prediffer types, described later in this topic, that enable you to apply the plugins either manually or automatically. There is no automatic mode for editor complement plugins.

When you apply plugins to a selected file using automatic mode, WinMerge searches its list of suggested plugins for that file type, and applies the first plugin whose name matches. The search is performed in alphabetical order, so if there are multiple suggested plugins for a file type, only the first one found is applied.

3. Applying plugins

The following subsections describe how to apply each type of plugin. The methods are different for each type of plugin, and also vary depending on whether you are comparing folders or files.

3.1. Applying editor complement plugins in the File Compare window

With your cursor in either File pane of the File Compare window, click EditScripts and choose one of these functions:

  • MakeUpper

  • MakeLower

  • InsertDate

  • InsertTime

The functions are contributed to the Scripts menu by the editor addin.sct and insert datetime.sct plugins.

[Note] Note

Editor complement plugins are not available in the Folder Compare window.

3.2. Applying unpacker plugins in the Folder Compare window

Before applying unpacker plugins, you can set its mode to either automatic or manual mode.

  • To set automatic mode for this type of plugin, click PluginsAutomatic Unpacking.

  • To set manual mode, click PluginsManual Unpacking.

Remember to click F5 to reload the Folder Compare window using the new setting.

3.2.1. Using automatic mode

To apply plugins when automatic unpacking is set, simply launch a compare operation on a file in the Folder Compare window. If the file's type suggested unpacker plugin (if any) preprocesses the file before WinMerge opens it in the File Compare window.

For example, suppose you right-click an MS Word doc file and choose Compare (also assume that the CompareMSWordFiles.dll plugin is available). WinMerge converts the doc file (or rather, a copy of it ) to a plain text file and opens it in the File Compare window.

3.2.2. Using manual mode

Manual mode enables you to choose a different unpacker plugin than the one that is selected for you in automatic mode. You can also launch the compare using no plugin.

To apply plugins when manual unpacking is set:

  1. Select the file you want to compare.

  2. Click PluginsEdit with Unpacker.

    This menu item is enabled only if the selected file's type is supported by an available unpacking plugin.

  3. In the Select Unpacker dialog:

    1. Configure automatic plugin selection or choose a plugin manually:

      • To use automatic mode (which applies the first available plugin), verify that <None> is displayed in the File unpacker control.

      • To choose a different plugin (if available), use the File unpacker control to choose the plugin.

        By default, this control lists only suggested plugins for the file type you selected to compare. To see all available plugins, enable the option, Display all packers, don't check the extension.

      • To launch the compare without using any plugin, choose <None> in the File unpacker control.

    2. Click OK to close the Select Unpacker dialog.

  4. Click OK to close the Select Unpacker dialog and launch the file comparison.

3.3. Applying unpacker plugins in the Select Files or Folders dialog

You can use the Select Unpacker dialog to apply a plugin when you launch a file comparison from the Select Files or Folders dialog. See Selecting an unpacker for file comparisons for details.

3.4. Applying prediffer plugins in the Folder Compare window

With prediffer plugins, you set the mode (Auto prediiffer or No prediffer) for individual files. (Contrast this with unpacker plugins, where you set the mode for all files.) That is, some files in the same folder have different prediffer modes.

To set the mode for one or more files in the Folder Compare window, right-click the files and choose Plugin SettingsPrediffer Settings, then choose one of the submenu options:

  • Auto Prediffer selects the first prediffer plugin available for the file type.

  • No prediffer means that no prediffer plugin is used.

Click F5 to update the window.

[Note] Note

When you open a subfolder during a non-recursive compare, the mode is always reset to No prediffer.

When you open a file from the Folder Compare window, your prediffer setting for that file is applied before the File Compare window is opened.

3.5. Applying prediffer plugins in the File Compare window

In the File Compare winodw, you can apply a prediffer plugin by clicking PluginsPrediffer and choosing one of the plugins in the list. Suggested plugins are indicated at the top of the list. The files are compared again after the plugin is applied, so you don't need to rescan the files.

4. Available plugins

4.1. CompareMSExcelFiles.dll

Displays the text contents of a Microsoft® Excel file, stripping away all formatting and embedded objects.

Category: Unpacker
File filter: *.xls
Packing: No
Requirement: Microsoft® Excel, Visual Basic runtime library

4.2. CompareMSWordFiles.dll

Displays the text content of a Microsoft® Word file, stripping away all formatting and embedded objects.

Category: Unpacker
File filter: *.doc, *.dot
Packing: No
Requirement: Microsoft®Word, Visual Basic runtime library

4.3. DisplayXMLFiles.dll

This plugin pretty-prints XML files nicely by inserting tabs and line breaks. This is useful for XML files that do not have line returns in convenient locations.

Category: Unpacker
File filter: *.xml
Packing: No

4.4. editor addin.sct

Adds two functions to the EditScripts menu:

  • MakeUpper convert the selection to UPPER CASE.
  • MakeLower convert the selection to lower case.
Category: Editor complement

4.5. IgnoreColumns.dll

This plugin ignores characters at specified columns. The first column is number 1

Note that this plugin does not support files with tabs: the plugin does not fail, but all tabs are be treated as normal characters.

To specify columns, rename the dll using following fields as parameters:

  • Delimiters between ranges: _ or ,
  • Delimiters between min and max: anything else
  • Min and max are included.
  • When max = min, max can be omitted.

Example 1. IgnoreColumns.dll examples

IgnoreColumns _ 3 _ 10 - 20 _ 32 - 33.dll
Ignore all characters at column 3, and in columns 10 to 20, and 32 to 33.
IgnoreColumns_1,30 to 40.dll
Ignore all the characters in column 1, and in columns 30 to 40.

Category: Prediffer
File filter: *.txt

4.6. IgnoreCommentsC.dll

The plugin ignores comments within //... and /* ... */ delimiters in C, C++, PHP and JavaScript files.

Category: Prediffer
File filter: *.cpp, *.cxx, *.h, *.hxx, *.c, *.php, *.js,

4.7. IgnoreFieldsComma.dll

This plugin is for files with fields and commas as delimiters (CSV files, for example). It ignores the delimiter characters. The first field is number 1.

To specify the delimiters, rename the dll using the same parameter fields used for IgnoreColumns.dll.

Category: Prediffer
File filter: *.csv

4.8. IgnoreFieldsTab.dll

This plugin is for files that use fields and tabs as delimiters (for examle, Excel files saved in the *.txt format). It ignores the delimiter characters. The first field is number 1.

To specify the delimiters, rename the dll using the same parameter fields used for IgnoreColumns.dll.

Category: Prediffer
File filter: *.txt

4.9. IgnoreLeadingLineNumbers.dll

This plugin ignores the leading line numbers in text files (for example, NC and BASIC files).

Category: Prediffer
File filter: *.nc

4.10. insert datetime.sct

Adds two functions to the EditScripts menu:

  • InsertDate insert date in the current locale format.
  • InsertTime insert time in the current locale format.
Category: Editor complement

4.11. RCLocalizationHelper.dll, RCLocalizationHelperU.dll

This plugin preprocesses RC files by stripping out localized strings, to enable comparing different language versions of the same RC file and ignoring the translations.

RCLocalizationHelperU.dll is the Unicode version.

Category: Prediffer
File filter: *.rc

4.12. WatchBeginningOfLog.dll, WatchEndOfLog.dll

For long LOG files, often only in the first lines or in the last lines are significant.

  • WatchBeginningOfLog.dll truncates the files to the first 1/10th.
  • WatchEndOfLog.dll truncates the files to the first 1/10th.
Category: Unpacker
File filter: *.log
Packing: No

Developers can find information and code examples in the source package, under the Plugins folder.

5. Requirements

5.1. Windows Script Host

Some editor complement plugins require this optional component from Microsoft®.

It should already be included in your version of Windows, unless you use some really old pre Windows XP version.

5.2. Visual Basic runtime library

Some plugins require the Visual Basic runtime library to work.

You can download the required file msvbvm60.dll, or use the Run-Time Redistribution Pack from Microsoft®. If you don't need the plugin, you can safely remove it.