7-Zip vs The Unarchiver

7-Zip

• Windows users who need to open or create archives at no cost
• Compressing large folders into 7z archives with a high compression ratio
• Organizations, since the license allows use on commercial computers without registration

The Unarchiver

• Mac users who need to open RAR, 7z and other archive formats
• Opening old archives in formats such as StuffIt or DiskDoubler
• Archives whose file names use non-Latin characters

7-Zip

• The graphical app and File Manager are for Windows; the Linux and macOS downloads are console versions only.
• RAR archives can be unpacked but not created; RAR is listed under unpacking-only formats.
• Help comes through the forum, bug reports and feature request systems on the project's SourceForge page.

The Unarchiver

• It only extracts: the site lists the formats it can open and describes no way to create archives.
• The app is for macOS 10.13 or later. Windows and Linux get only the unar and lsar command-line tools, with no graphical app.
• Some formats are partly supported: StuffIt X is partial, Ace 2.0 and later is unsupported, and multi-part ARJ archives do not work.
• Version 4.3.9 added product usage analytics and a survey invitation, according to the App Store release notes.

7-Zip

7z format with LZMA and LZMA2

Creates 7z archives using LZMA or LZMA2 compression. The format supports solid compression, Unicode file names and compressed archive headers.

Wide format support

Packs and unpacks 7z, XZ, BZIP2, GZIP, TAR, ZIP and WIM, and unpacks many more formats, including RAR, ISO, DMG, CAB, MSI, VHD and VMDK.

AES-256 encryption

Archives in the 7z and ZIP formats can be encrypted with AES-256.

Windows shell integration and File Manager

Integrates with the Windows shell and includes its own File Manager for browsing and working with archives.

Command line version

A command line version ships with the Windows release, and console builds are offered for Linux and macOS on x86 and ARM processors.

Self-extracting archives

Can create self-extracting archives in the 7z format.

The Unarchiver

Common archive formats

Lists full support for Zip, Zipx, RAR, 7z, Tar, Gzip, Bzip2, LZMA and XZ, plus CAB, MSI, NSIS installers and common disc images such as ISO and BIN.

Encrypted and multi-volume archives

Opens RAR archives with encryption and multiple volumes and Zip archives with AES encryption, and can join split files named .001, .002.

Older and unusual formats

Unpacks formats such as StuffIt, DiskDoubler, LZH, ARJ and ARC, and Linux packages such as RPM and Deb. Support for some, including StuffIt X and Ace, is partial.

Filename encoding detection

Tries to detect and handle the filename encoding used inside an archive, so files named in non-Latin characters are not garbled.

Default app for archives

Can be set as the default app for archive files through Finder's Get Info window, after which archives open with it automatically.

unar and lsar command-line tools

The same unarchiving code is offered as two command-line tools, unar and lsar, which run on macOS, Windows and Linux.

7-Zip

• 7-Zip$0

  The complete archiver for Windows, plus console versions for Linux and macOS. Most of the code is under the GNU LGPL.

The Unarchiver

• The Unarchiver$0

  The complete app for macOS 10.13 or later, with every supported format included and no in-app purchases.