AppleInsider has found out what exactly Apple has been doing to shrink application size, in the successor to Leopard, called Snow Leopard deliver performance improvements and resource footprint reductions. One measure is the fact that Apple has removed the various localisation files from each application, relying on a centralised container instead from which application can draw the things they need. Another measure is the compression of Interface Builder's NIB files; NIB files also contain the graphical resources. In addition, Apple lost weight by deleting the designable.nib files from bundles - they are the xml files used during development, and they shouldn't be in the final builds, but due to an error by Apple, they were included anyway in Leopard's bundles. Compressing the NIB, xml, and html files in Leopard's mail already reduces Mail.app from 289 to 96.6MB.
While Apple may likely be expanding the use of background file compression to save space in Snow Leopard, today's Mac OS X Leopard is unnecessarily overweight due to an error Apple made when packaging the system, according to a developer who asked to remain anonymous. Leopard apps all contain superfluous designable.nib files that should have been removed in the Golden Master. "Mail alone has around 1400 of these files, taking up almost 200 MB of disk space," he noted.