TextWrangler is capable of comparing text files and highlighting the differences between them, and it’s super easy to do it:
1. Open the two documents that you’d like to compare in TextWrangler.
2. Highlight the 2 files you want to compare in the window on the left, then right click on them and select the option ‘Compare‘.
TextWrangler will show you exactly which lines were modified so you can easily compare and/or copy them from one file to the other.