The format is a specialized open-source compression standard designed for maximum data density, deduplication, and archival reliability. Unlike traditional formats like ZIP or RAR, ZPAQ is a "journaling" format, meaning it stores every version of a file over time, allowing you to "roll back" to any previous state.
PeaZip free archiver utility, open extract RAR TAR ZIP files
PeaZip is the most user-friendly GUI-based extractor for ZPAQ files. It is free, open-source, and supports over 200 archive formats.
For the most stable and feature-complete experience, the original command-line tool by Matt Mahoney is recommended.