The Relationship Between Unrar and RARLAB

This article explains the relationship between the Unrar utility and RARLAB, the software company behind the RAR format. While RARLAB is the official developer and intellectual property owner of the proprietary RAR compression algorithm, Unrar is a specialized, free-to-use extraction tool created by the same company to allow users and developers to unpack RAR files across various platforms.

RARLAB is the official organization founded by Eugene Roshal, the computer engineer who invented the Roshal Archive (RAR) file format. RARLAB develops, maintains, and licenses the flagship commercial compression software WinRAR, as well as command-line versions of the tool for different operating systems. Because the RAR compression algorithm is proprietary and patented, RARLAB holds exclusive control over the technology used to create .rar archives.

Unrar is an official command-line utility developed directly by RARLAB specifically for decompression. Unlike WinRAR, which is a full-featured commercial tool capable of both compressing and decompressing files, Unrar is strictly limited to extracting, listing, and testing the contents of existing RAR archives.

To ensure that users on non-Windows platforms (such as Linux, macOS, and FreeBSD) can open RAR files, RARLAB provides Unrar as both pre-compiled binaries and public C++ source code. This source code forms the backbone of extraction features in many popular third-party tools, including 7-Zip and various Linux archive managers.

Although RARLAB provides the Unrar source code freely, the relationship comes with strict licensing conditions. The Unrar source code is released under a proprietary "freeware" license rather than a standard open-source license like GPL or MIT. RARLAB's license permits anyone to view, modify, and distribute the code for extraction purposes, but it explicitly forbids developers from using the code to reverse-engineer or reconstruct the proprietary RAR compression algorithm.

In summary, Unrar is an official, purpose-built decompression tool created and governed by RARLAB to facilitate widespread access to the RAR format while protecting their core intellectual property.