The .xib file extension is most commonly associated with Interface Builder files. Interface Builder is a graphics editing software that is used to design and test the user interfaces of a variety of software products. The files with the .xib file extension contain development time format files. These files contain the interface files created with the Interface Builder software.
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If you have additional information about the XIB file format or software that uses files with the XIB suffix, please do get in touch - we would love hearing from you.