Beginning with Version 2.14, WinMerge ended support for older 32-bit Windows systems, including Windows 9x, ME, and NT4. In addition, WinMerge version 2.16 does not support Windows 2000.

Previously, WinMerge provided an ANSI (8-bit) executable, WinMerge.exe, that was designed around the old Windows codepages. WinMerge.exe internally stored only the ANSI characters supported by the Windows codepage. This executable had severe limitations for working with Unicode: if you opened a Unicode file, the characters were converted to the Windows ANSI codepage. Because there are over 100,000 Unicode characters, and only 256 can be represented in the ANSI character set, data loss could occur. Conversion might be approximate (for example, accents are lost) or impossible: characters were replaced by question marks ( ? ).

WinMerge.exe also could not open files with names outside the current ANSI codepage. For example, on an English system, WinMerge.exe could not open a file with a Hebrew name.

WinMerge developed the Unicode-enabled WinMergeU.exe executable to work with newer, Unicode-based Windows systems. WinMergeU.exe has none of the limitations of the ANSI executable.

WinMergeU.exe has been installed by default for some time, and since few ANSI-based Windows systems remain, the value of maintaining WinMerge.exe is minimal. As of Version 2.14, WinMerge no longer includes WinMerge.exe in the installer.

Browse in the folder contents to the folder you want to compare. Do not select any of the files or subfolders, just click Open when Folder Selection is displayed in the File name field. If you already selected a files or subfolders, just type a random string in the File name field and click Open. If the file name you enter is not found, WinMerge opens the folder.

There are currently no plans for cross-platform support but you can try the unofficial version WinMerge 2011 by Jochen Neubeck. This version should work with Wine also under Linux.

Providing an integration with CVS is of questionable value because there already are so many good CVS clients. However, WinMerge does provide an integration with the diff function of one of those clients, TortoiseCVS (as described in Using WinMerge with other tools). Also, WinMerge can resolve conflict files (see Resolving conflict files).

MRU is an abbreviation for “Most Recently Used”, and refers to the history lists in the Select Files or Folders dialog. The list contain the last twenty paths used on each side.

OpenOffice files are archives. To be able to open them in WinMerge, you have to configure archive support:

This is because WinMerge always uses the Quick Contents file compare method for large files. This method enables WinMerge to compare large files more efficiently. To test if this is causing the behavior you're seeing, you can try raising the Quick Contents threshold for large files. See the discussion of this method in Starting a folder compare operation to learn how.

Maybe your files have different line ending styles (for example, Windows and Unix). By default, WinMerge compares line ending styles. To disable it, click Edit → Options. In the Compare page, enable (check) the option, Ignore carriage return differences.

This is what we call a lossy conversion.

For ANSI files, this is probably due to code-page problems. To troubleshoot, click Edit → Options. Then in the Codepages page, see if the option Detect codepage info is checked. If it is, deselect the option, click OK, and see if that helps.

Unfortunately, WinMerge supports only non-proportional fonts.

When Automatic Rescan is enabled (in the Editor page of Options), WinMerge delays rescanning while you edit files. That is, no rescanning occurs until shortly after you stop typing. Without this delay, WinMerge would rescan after every typed character, making the editing process too slow. The delay especially improves editing bigger files, which can take several seconds to rescan.

Yes, there is basic printing support: click File → Print.

Yes, you can show only different lines by clicking View → Diff Context → 0 lines.

Open WinMerge from the command line, and include the -e switch.

Use the -x command line switch.

Have your external program invoke WinMerge with the /ub option, which tells WinMerge to not add the files to the MRU.

Create a batch file that contains one of these lines (but not both):

Call this batch file from your program.

Perry-style patches are zip files containing original and changed files in different directories. WinMerge has internal support (surprise!) for handling these files: just launch a compare operation, selecting the zip file for both the left and right sides. WinMerge opens the contents of the zip file in a Folder Compare window, comparing the original and changed files.

Yes: click the Options button (or click Edit → Options). In the Archive Support page, enable the Detect archive type from file signature option.

Open the file in Windows Notepad (for example, click Start → (All) Programs → Accessories → Notepad). Click File → Save As, and in the Save As dialog, scroll to the Encoding item at the dropdown list. The possible values include:

No. It might be added in later versions. Until then, you can use the Win32 port of diffutils. The latest version of diffutils (and patch) can be downloaded from the SourceForge GnuWin32 project page: https://sourceforge.net/projects/gnuwin32.

You can apply patches using the experimental plugin ApplyPatch.sct. The extensions of patches supported by the plugin are .diff or .patch.