Frequently asked questions

1. General questions


Does WinMerge run on older Windows versions?

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.


I want to compare folders, but I cannot select a folder in the Browse dialog.

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.


Do you have any plans to support other operating systems besides Windows?

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.


Why is there no CVS integration?

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).


What is an MRU list?

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.


Can WinMerge open OpenOffice files?

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

  • In WinMerge, click the Options button (or click EditOptions). In the Archive Support page, enable the Detect archive type from file signature option


Why do large files sometimes show up as different in the Folder Compare window, but identical in the File Compare window?

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.

2. File comparing


Why do my files have all lines marked as different (colored), even though I know all the lines are not different?

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

3. Questions about editor


I see question marks instead of letters in files.

This is what we call a lossy conversion.

For ANSI files, this is probably due to code-page problems. To troubleshoot, click EditOptions. 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.


I cannot select proportional fonts for editor.

Unfortunately, WinMerge supports only non-proportional fonts.


What is delay of automatic rescan? Why it is needed?

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.


Can I print files from the File panes in the Compare Files window?

Yes, there is basic printing support: click FilePrint.


Can I hide similar lines in a file comparison, so that only different lines are visible?

Yes, you can show only different lines by clicking ViewDiff Context0 lines.

4. WinMerge as external compare or diff-tool


I want WinMerge to close with a single Esc press after I'm done?

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


I don't want to see the Files Are Identical message when I compare identical files, I just want WinMerge to quit.

Use the -x command line switch.


How can I avoid filling the Select Files or Folders dialog history lists with temporary paths?

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


But the program I'm using doesn't allow command line parameters!

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

  • CALL "<winmerge path>\WinMerge" /e /u %1 %2 %3
  • start "WinMerge" "<winmerge path>" /e /u %1 %2 %3

Call this batch file from your program.

5. Archive support


How can I open the Perry-style patch files that WinMerge developers use when submitting patches?

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.


Can WinMerge open archive files with non-standard file-extensions? (For example .jar files as zip-files)

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

6. Text encoding (codepages)


How do I tell if my file is coded in the local Windows (ANSI) codepage?

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

  • ANSI: The file is apparently in the local Windows codepage. If the file is entirely in English and normal punctuation, then the file is also in ASCII.

  • Unicode: The file is probably in the default Windows Unicode encoding, UCS-2LE.

  • UTF-8: The file is in the cross-platform Unicode encoding, UTF-8.

  • Unicode big endian: The file is in a different Unicode encoding that is little used or supported in Windows, probably UCS-2BE.

7. Patch files


Is there way to create patch files from the command line?

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:


Can patches be applied using WinMerge?

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