KDiff

KDiff is a software that is able to spot all the differences between text files. It if very useful for programmers to compare 2 files and see what has been modified. It displays with different colors what will find different, including white space or indentation.

You can compare 2 or 3 files, not just 2. The differences are shown character by character, which makes from this tool a very useful instrument to save time when you try to spot coding errors.