KDiff3: When You Need to Know What the Diff Is

Admit it, we all need one sometimes. In development projects configuration management is often more intention than reality. And when that happens we need to use a file comparison tool to figure out what exactly is going on with the code, which version of the file is the right one, and where errors may have been introduced. This can happen when:

  • Porting older files from legacy software
  • You have multiple people modifying files without proper management
  • Or just customizing versions of files such as configuration files

Kdiff3 is an open source file comparison tool supported on Windows, OSX, and various flavors of Unix/Linux. It provides a easy to understand GUI for comparing files, directories, and merging files. Graphical front ends to the GNU diff utilities abound, but Kdiff3 offers some extra features to make every developer’s life easier.

Whitespace changes will show up on comparison tools, but it is often hard to see these differences when only the line is highlighted. KDiff highlights the exact change so you know if it is a matter of a tab vs. spaces in a glance.

It also categorizes the differences it finds as “important” or “not-so-Important”. You have control over whether the categorization is on or off. Whitespaces are in the not-so-important category. Case sensitivity and numbers can also be handled differently.

You probably thought that the 3 in Kdiff3 is a version number. But you’d be wrong. The software offers the ability to do a 3-way merge. If a base file was modified independently by two developers, this capability allows the changes to be viewed at one time. KDiff documentation claims that its algorithms usually get this three-way comparison right when others get it wrong.

If you work on a development team KDiff3 is worth checking out to see if it can improve your productivity by more accurately identifying differences and letting you chose what differences matter.

Do you already have a favorite file comparison tool?