What is the difference between NIB and XIB Interface Builder file formats?

Question

What is difference between nib and xib in Interface Builder files?

Answer 1

XIBs are flat files rather than being a bundle. This makes it easier for SCM(source control management) systems to deal with. When you compile your app, the XIB is compiled into a NIB file for inclusion in your app.

The compiled NIB that is included in the app bundle is no longer editable in Interface Builder and is much smaller than the equivalent XIB or legacy NIB file.