The classic tool for efficient file synchronisation and backup, transferring only the differences between source and destination with its delta algorithm. For nearly three decades the workhorse behind mirrors, backups and archives everywhere.
The Preservation Rating scores how well this entry is archived — not how good the software is. It's calculated automatically from what's already on this page: working mirrors, documentation, a reproducible build, a clearly identified license, and complete metadata. Nothing here is entered by hand; it updates itself whenever the entry changes.
