Debdelta is a program suite designed to compute changes between Debian packages. These changes (deltas) are similar to the output of the "diff" program in that they may be used to store and transmit only the changes between Debian packages.

This suite contains 'debdelta-upgrade', that downloads deltas and use them to create all Debian packages needed for an 'apt-get upgrade'. It may be used in a Debian/unstable host (to speed up download of new packages), or in a Debian/stable host (for security updates).

Similarly, when this package is installed, the 'cupt' package manager will use deltas to upgrade the host.