Versions does not have an integrated difference viewer, but instead lets you choose an external application to show file comparisons. An external application is required to view comparisons.
By default, Versions uses “FileMerge”, part of the Xcode developer tools, to perform comparisons. Several other applications can be selected from the “Preferences” window. A full list of options is:
For information on how to use other external applications or customize comparing behavior, see the section: Custom comparison scripts.