Here’s the Deal

P4Merge vs Kdiff3

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When comparing P4Merge vs Kdiff3, the Slant community recommends Kdiff3 for most people. In the question“What are the best folder/file compare/diff tools for either OSX, Linux or Windows?” Kdiff3 is ranked 3rd while P4Merge is ranked 5th. The most important reason people chose Kdiff3 is:

For modern version control systems, 3way merge support is a basic requirement, but many other open source diff viewers do not adequately handle 3way merges.

Specs

PlatformsWindows; Mac; Linux

LicenseFree

PlatformsWindows, Linux, Mac

Ranked in these QuestionsQuestion Ranking

Common Questions

What are the best folder/file compare/diff tools for either OSX, Linux or Windows?

What are the best diff tools for Git?

What are the best visual merge tools for Git?

What are the best Linux diff tools?

What are the best merge applications for Git?

What are the best free 3-way merge tools for Windows?

What is the best tool for resolving conflicts when merging file changes?

Pros

Pro
Free

P4Merge is free of charge.

Pro
3 way merge support

P4Merge presents merge information in 4 panes - BASE, LOCAL, REMOTE and MERGE_RESULT.

Pro
Detects minimal changes without having a common ancestor

After a merge sometimes you have conflicts. You can resolve them by using a merge tool. You can run git mergetool --tool-help to get more details about what tools are supported.

You will get an output like the following
git mergetool --tool=<tool> may be set to one of the following:

      p4merge
        tortoisemerge
        vimdiff
        vimdiff2
        vimdiff3

The following tools are valid, but not currently available:

        araxis
        bc
        bc3
        codecompare
        deltawalker
        diffmerge
        diffuse
        ecmerge
        emerge
        gvimdiff
        gvimdiff2
        gvimdiff3
        kdiff3
        meld
        opendiff
        tkdiff
        winmerge
        xxdiff

Some of the tools listed above only work in a windowed environment. If run in a terminal-only session, they will fail.

Pro
Also has image diffing

For those who are working in both text based source code or files, as well as images, its nice to have the diff functionality of both present in the same product.

Pro
Cross-platform with a good Mac port

P4Merge works on Windows, Linux and OS X.

Pro
Supports 3 way merges

For modern version control systems, 3way merge support is a basic requirement, but many other open source diff viewers do not adequately handle 3way merges.

Pro
Free and open source

KDiff3 is completely free to download and use. It's also open source released under the GPL.

Pro
Can compare directories

It is able to compare whole directory trees.

Pro
Supports editing files directly

In addition to comparing two files it also allows you to edit the merge result right in place.

Pro
Diff by character not by lines

On comparing two files, difference is shown by characters; not by lines.

Pro
The UI is customizable

Allow customizing colors regardless of user/system theme.

Pro
Supports manual code aligning

With selecting code in one window and hitting Ctrl+Y, then selecting some other code in second window and also hitting Ctrl+Y you can manually align the code.

Pro
Preprocessing before calculating differences

There are options that may pre-process compared files before Kdiff3 actually do a comparison - to ignore for example automatically generated dates and/or revision numbers added by commit hooks.

Pro
Context menu shortcut

You can right-click a folder/file and the options:

Save <file> for later
Compare with

will be available, making launching KDiff3 really convenient.

Ad
Cons

Con
Directory comparison is not supported

With P4Merge it's impossible to compare two different directories to find differences.

Con
Cannot do inline diffs

Comparison of 2 files is always side-by-side and there's no option for inline views. Overall a rather poor and confusing UI in general.

Con
Confusing GUI

4 sub-windows (when you really only need 3), a lot of different colors and even more confusing result-window. No links what has changed between versions and and the result. It clearly shows it's dated or rather outdated. Great if you ever need to do a command line merge, otherwise it sucks.

Con
No precise editing of the compared files

Precise work line-after-line is not possible. Only a version after the automated merge-step is editable, but not the two files separately.

Con
No longer supported by Homebrew for MacOS

Cannot be installed easily on Mac as of Aug 2019.

Con
Problems when files have different number of lines

For example, if you add 3 lines: A, B and C locally but on the other change there are only A and C, Kdiff3 will work out that A was added, then it says that B conflicts with C but adds C again anyway.