Martin Pool,

The librsync library does network delta-compression of streams and files. The algorithm is similar to that used in the rsync and xdelta programs. Unlike diff and xdelta, librsync does not require access to both of the files on the same machine, but rather only a short signature of the old file and the complete contents of the new file.

librsync ships with a tool called rdiff which does delta compression from the command line or from scripts.

librsync does not speak the application-specific protocol used by rsync. They only share an algorithm, not any code.

The current release is librsync-0.9.6, which was released in 2004 and seems stable.


From April 2014, the code has been moved to



librsync is used by: Dropbox, rdiff-backup, duplicity, and others. If you use it, please let me know.