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ZIP vs 7z vs RAR: which archive format?
By Himanshu Ranjan · Updated 8 November 2026
Choose ZIP for sharing, since every major operating system opens it natively. Choose 7z when you control both ends and want AES-256 encryption and strong compression, using the open 7-Zip tools. Choose RAR only if the recipient requires it, because creating RAR files needs licensed software, though many tools can extract them.
ZIP: the default
Wikipedia says major operating systems, including Windows, macOS, Linux, Android, iOS and ChromeOS, read ZIP natively, usually in the file manager. Deflate is its most common compression method, and each file is stored separately, so you can extract or add a file without processing the whole archive. On a Mac, Finder's Compress command makes a ZIP, and FileDial's Archive › Make ZIP does too, writing a new copy beside the original.
The weak point is the original password scheme. Wikipedia describes it as seriously flawed, with known-plaintext attacks a particular risk. Newer AES encryption has been documented since spec version 5.2, and tools like 7-Zip use it.
7z: strong and open
7z supports several methods, including LZMA with a dictionary of up to 4 GB and LZMA2, which improves multithreading. It uses AES with a 256-bit key and can also encrypt file names. The 7-Zip program is under the GNU LGPL, and the format specification has shipped with its source since 2015. Wikipedia notes it does not store file system permissions, which can make it unsuitable for backups on UNIX-like systems. It also lacks the recovery feature that RAR offers. FileDial can write one with Archive › Make 7Z.
The catch is reach: a recipient needs software that opens 7z, since macOS does not read it natively.
RAR: proprietary
RAR was created in 1993 by Eugene Roshal. It is proprietary: Wikipedia says only licensed tools can create RAR files, including WinRAR, RAR for Android and the command-line RAR, while extraction is widely supported, including by the free unrar tool, 7-Zip and, in Windows 11 from version 23H2, natively. Version 2.9 added encryption and optional recovery volumes, and version 5.0 raised AES encryption to 256 bit. Recovery volumes are RAR's distinctive feature for damaged downloads.
On a Mac, creating RAR is awkward because it needs licensed software. If someone asks for RAR, ask whether ZIP or 7z would do.
Choosing, and passwords on a Mac
For anything shared with the public or a client, use ZIP. For your own backups or large archives where size matters and you control both sides, use 7z. For passwords, FileDial's Protect › Add password… and Archive › ZIP with password… offer Standard (ZipCrypto), which opens in Finder, and Stronger (AES-256), which needs 7-Zip or The Unarchiver. Given the ZipCrypto weakness, pick AES-256 for anything sensitive and send the passphrase separately. Extract › Extract with password… opens protected archives and Extract › Extract here unpacks into a folder named after the archive.
Archive › Split into 2 GB ZIP parts (WeTransfer) handles files too large for a transfer service, and Developer › Test archive integrity writes an OK or FAILED report without extracting.
- Compatibility: ZIP > RAR (extract) > 7z
- Compression strength: 7z usually strongest, ZIP weakest
- Open and free to create: ZIP and 7z; RAR is not
- Built-in recovery data: RAR
- Strong encryption: 7z and RAR 5 (AES-256), ZIP with AES
Mistakes and practical advice
The first mistake is compressing files that are already compressed. JPG, MP4, MP3 and most PDFs shrink very little in any archive format, so choosing 7z for a folder of photos mainly costs time. Archives help most with text, documents, code and uncompressed formats such as WAV. For photos and video, an archive is mostly a convenient bundle.
The second is sending a format the recipient cannot open. A 7z or RAR attachment to a non-technical client produces a support email. Use ZIP unless you know the other side has the software, and mention what they need if you use something else.
The third is weak password handling, covered above: prefer AES-256 for sensitive data, use a long passphrase, and send it separately. Do not rely on a ZIP password to hide a file name or to stop a determined attacker if the old ZipCrypto method was used.
Fourth, archives as backups. 7z does not store file system permissions, which Wikipedia says can make it unsuitable for backups on UNIX-like systems, and any single archive is one point of failure. Use Time Machine for backups and archives for transfer and storage of finished work. Developer › Test archive integrity writes an OK or FAILED report without extracting anything.
Fifth, unpacking untrusted archives carelessly. An archive from an unknown sender can hold malware or very many files. Extract into a new folder, look at the contents first with Extract › List contents, which writes a text listing and extracts nothing, and let macOS's own Gatekeeper checks do their job on anything you open.
Finally, remember what macOS does natively: Finder compresses to ZIP and opens ZIP. Add other formats only when a real need appears.
Questions
Which compresses best, ZIP or 7z?
7z with LZMA generally compresses harder than ZIP's Deflate, though results depend on the files. Text and documents shrink a lot more than photos, video and PDFs, which are already compressed and shrink little in any format. Test on a sample before switching.
Can a Mac open RAR files?
macOS does not open RAR files natively. Free tools such as The Unarchiver or 7-Zip can extract them. Creating RAR files requires licensed software such as WinRAR, since Wikipedia says only licensed tools can create RAR, so if you need to send an archive, use ZIP or 7z instead.
Is a ZIP password secure?
The original ZipCrypto scheme is weak, and Wikipedia calls it seriously flawed. Use AES-256 with a long passphrase instead. In FileDial choose Stronger (AES-256), which needs 7-Zip or The Unarchiver to open, and send the passphrase by a separate channel rather than with the file.
Should I use 7z for sending files to clients?
Usually no. Use ZIP unless you know the client can open 7z, because compatibility matters more than saving a few percent in size. A recipient who cannot open your archive loses more time than a slightly larger file ever would, and ZIP opens natively on every major system.