The often overlooked Xcode FileMerge app lets you spot what's changed between two files. Here's how to spot the differences using the tool.

Beyond Compare is a file compare and directory sync utility wrapped in one. Beyond Compare Standard edition ($30) is a powerful utility for tracking down differences between files and folders.

With files, you may want to look at changes in source code, HTML code, or other data. VisualDiffer will spot these differences for you.