7z vs ZIP vs RAR - Choosing by Compression Ratio, Speed and Compatibility

The short answer: ZIP to send, 7z to shrink, RAR to open

The differences between the three formats come down to three questions: where it opens, how small it gets, and who can create it. Send ZIP to other people, use 7z when you want your own archives as small as possible, and treat RAR as a format you open when someone sends it.

Checked in October 2026 against each vendor's documentation and on macOS 26.5.

Garbled names are a weakness of ZIP; 7z and RAR 5.0 archives are built to avoid them (see why ZIP file names turn into garbled text).

ZIP: the format that opens everywhere

ZIP was first published by PKWARE in 1989, and its specification, APPNOTE.TXT, has been revised many times since (the final version as of October 2026 is 6.3.10 from November 2022). Each file inside is compressed separately, and a numbered field records the method. Nearly every ZIP uses method 8, Deflate. The specification also lists method 14, LZMA, among others, but few tools open anything other than Deflate.

ZIP's strength lies in that file-by-file design. Reading the central directory is enough to pull out one file without decompressing the others, and if the archive is damaged partway, the undamaged files can usually still be extracted. That ease of handling is exactly why built-in apps such as the iPhone Files app and Files by Google on Android support ZIP. Plenty of tools create it, too: macOS ships with the ditto command and Info-ZIP's zip command, and Python's zipfile module writes ZIP files as well.

Its weak points are encryption and name encoding. The original encryption (ZipCrypto) is called weak by APPNOTE 6.3.10 itself, while ZIP files using the stronger AES may not open in built-in apps. Japanese file names can garble depending on the system when the ZIP lacks the UTF-8 flag (bit 11 of the general purpose bit flag). How to fix garbled names is covered in why ZIP file names turn into garbled text, and the two encryption families in how to open a password-protected ZIP on a phone.

7z: solid archives that shrink well, if the other side can open them

7z is the format of Igor Pavlov's 7-Zip. The 7-Zip documentation lists its features as a high compression ratio, AES-256 encryption, solid compression, compressed headers and Unicode file names. In 7-Zip the default method is LZMA2 (as of October 2026), and the original LZMA, PPMd and BZip2 are available too. The 7z code is distributed under the GNU LGPL, and 7-Zip 26.05 was released on 21 October 2026.

Solid compression is one reason 7z shrinks so well. Several files are joined and compressed as one stream of data, so similarities between files (headers in the same format, recurring passages of text) are compressed together. The trade-off is that pulling out one file near the end means processing the data before it, and damage partway through can make the data after the damaged spot unreadable. The 7-Zip documentation also notes that the order of files inside a solid archive (by name or by extension) can change the compression ratio considerably.

Speed differs sharply between compressing and extracting. According to the 7-Zip documentation, LZMA compresses at about 2 to 8 MB per second on a 4 GHz CPU (two threads) and decompresses at about 30 to 100 MB per second (one thread). It is slow to create and quick to open.

7-Zip can apply AES-256 encryption to both 7z and ZIP files, and in 7z format it can also create self-extracting archives. Filters such as BCJ, which first transform predictable data like x86 or ARM64 executables before compressing it, are built into the 7z format as well.

RAR: strong recovery features, but WinRAR is needed to create it

RAR is a proprietary format created by Alexander Roshal, and the only tools that create it are RARLAB's WinRAR and the command-line RAR. WinRAR is paid software with a trial version you can use before buying (the stable release as of October 2026 is 7.23). For extraction alone there is the free UnRAR, and 7-Zip also opens RAR archives, RAR5 included, though it cannot create them. The UnRAR licence states that its source code may not be used to develop a RAR-compatible archiver or to re-create the proprietary RAR compression algorithm. This is one of the reasons so few programs can write RAR.

The RAR 5.0 format description from RARLAB shows the main features.

• Recovery record: optional data placed near the end of the archive, used to repair it when part of it is damaged
• AES-256 encryption: the key is derived from the password with PBKDF2. With the headers encrypted as well, anyone without the password cannot even see the list of file names
• Solid archives and volumes: there are flags for solid archives and for splitting an archive into several parts (volumes)
• Self-extracting archives: a self-extracting module (SFX) can be placed in front of the archive

In RAR 5.0 archives the name encoding is fixed as UTF-8: the file name in a file header is stored as UTF-8, so the kind of garbling seen with ZIP is unlikely.

Which to use, with measurements on documents

How much an archive shrinks depends on the contents. In October 2026 the author compressed 44 documents (HTML templates and JSON files, 616,972 bytes in total) into ZIP and 7z on a Mac running macOS 26.5. ZIP used the maximum setting of the macOS zip command (Zip 3.0, Deflate); 7z used LZMA2, created with bsdtar 3.5.3 on macOS. Each was measured once, so treat the numbers as a rough guide.

• Photos: JPEG is already compressed, so neither ZIP nor 7z shrinks it much
• Documents: ZIP came to 32.0 % (0.11 seconds), 7z to 22.4 % (0.42 seconds). Text is full of repetition, and here the gap is clear: 7z was about 30 % smaller than ZIP and took nearly four times as long

Put together, the choice by use case looks like this.

• Sending to someone: ZIP. It opens in the built-in apps whether the recipient uses Windows, a Mac or a phone. For Japanese names, switch to ASCII names or create the archive with the UTF-8 flag (bit 11 of the general purpose bit flag)
• Your own documents and data: 7z. Documents get visibly smaller than with ZIP, and AES-256 protects them. Damage spreads more easily in a solid archive, so keep a copy somewhere else as well
• Large batches of photos: for size alone the format hardly matters. Choose ZIP to send and 7z to protect them together, and decide by ease of opening rather than ratio
• Long storage on unreliable media: RAR with a recovery record is worth considering, but creating it requires WinRAR and the recipient needs a tool that opens RAR

Opening them: software or a browser tool when built-in support falls short

ZIP opens in the built-in apps of all four systems. 7z opens with built-in features on Windows 11 and macOS 26.5, and RAR opens with built-in features on Windows 11. Any other combination, especially a 7z or RAR arriving on an iPhone or Android phone, needs a dedicated app or a browser tool. Microsoft's announcement covered Windows 11, so a 7z or RAR file arriving on a Windows 10 PC also calls for 7-Zip or similar software, or a browser tool.

The piclab extractor opens ZIP, 7z and RAR entirely inside the browser. It handles password-protected and split archives, and the files are never sent anywhere. In Safari on iPhone or Chrome on Android, you can pick just the files you need and save them without installing an unzip app.

When something will not open, checking these three points before blaming the format usually settles it.

1. Do the extension and the contents match? A file named .zip may contain another format. If the built-in app says it is unsupported, try a tool that handles 7z and RAR
2. Are all the parts there? Put every part in one place: ZIP parts start at .z01, RAR parts at names such as .part1.rar
3. Password and encryption method: AES-encrypted ZIP files and RAR archives with encrypted headers only reach the password prompt in tools that support them

For the background of the format name, see the glossary entry ZIP; for the encoding behind Japanese file names, see Shift JIS.