diff is also the name of a famous console based file comparison utility that outputs the differences between two files. The diff utility was developed in the early 1970s on the Unix operating system. Typically, diff is used to show the changes between two versions of the same file. Modern implementations also support binary files.

Linux has many good GUI tools that enable you to clearly see the difference between two files or two versions of the same file. This roundup selects 6 of my favourite GUI diff tools, with all but one released under an open source license.

These utilities are an essential software development tool, as they visualize the differences between files or directories, merge files with differences, resolve conflicts and save output to a new file or patch, and assist file changes reviewing and comment production (e.g. approving source code changes before they get merged into a source tree).

They help developers work on a file, passing it back and forth between each other. The diff tools are not only useful for showing differences in source code files; they can be used on many text-based file types as well. The visualisations make it easier to compare files.

Diff Tools:

• Meld: Diff viewer and merge tool for GNOME
• xxdiff: File and directories comparator and merge tool
• Diffuse: Tool for merging and comparing text files
• KDiff3: Text difference analyzer for up to 3 input files
• Kompare: KDE diff tool
• DiffMerge: Visually compare and merge files