What Is a DIFF File?
A difference file records all the ways two text files are different. They’re sometimes called patch files and might use the PATCH file extension. This file type is normally used by software developers who are updating multiple versions of the same source code. Since it explains how the two versions are different, the program that uses the file can understand how the other files should be updated to reflect the new changes. Performing this type of modification to one or more files is called patching the files. Some patches can be applied to files even if both versions have been changed. These are called context diffs, unified diffs, or unidiffs. Patches in this context are related, but not the same, as software patches.
How to Open a DIFF File
DIFF files can be opened on Windows, Linux, and macOS with Mercurial. The Mercurial Wiki page has all the documentation you need to learn how to use it. Other programs that support this format include Kompare, GnuWin, and UnxUtils. If you use Kompare, open the file from the File > Open Diff menu. Read more about working with DIFF files in Kompare at KDE.org. Adobe Dreamweaver works as well, but we assume that would only be useful if you want to see the information that’s contained within it (if possible), not for actually using the file like you can with Mercurial. If that’s all you need to do, a simple free text editor works, too. If all else fails and you still can’t open it, it might be completely unrelated to difference/patch files and instead used by some other program. Use a free text editor, or the HxD hex editor, for help finding out what program was used to create that specific file. If there’s anything useful “behind the curtain,” so to speak, it’ll probably be in the header portion of the file.
How to Convert a DIFF File
Most file types can be run through a file converter tool to be saved in a new format, but there’s no reason to do that with a DIFF file. If your file happens to be unrelated to the difference file format, then the program that opens your specific file might support exporting or saving it to a new format. If so, that option is probably somewhere in the File menu.
Still Can’t Open It?
Some file formats use a similar extension—LDIF, RIFF, DIX, DIZ, and PAT are a few examples—but they aren’t the same thing. If your file isn’t opening using any of the programs mentioned above, check that you’re reading the extension correctly.
