ZIP, 7z or RAR: Which Archive Format Should You Send?

When you need to send a folder full of files, the obvious move is to put it in an archive. One file is easier to upload, easier to download and harder to lose part of.

Then comes the question of which format to use. Here's how the three common ones compare, and why the answer for most people is simpler than it seems.

ZIP

ZIP has been around since 1989 and it's supported everywhere. Windows and macOS can create and open ZIP files without installing anything. So can most phones.

• Pros: universal, fast, no extra software
• Cons: compression isn't the best, and the default password protection on many tools is weak (more on that below)

On Windows: right-click the folder, then Compress to ZIP file. On a Mac: right-click, then Compress.

7z

7z is the native format of 7-Zip, a free open-source program. It usually compresses noticeably better than ZIP, especially for text, code, logs and documents.

• Pros: better compression, strong AES-256 encryption, can encrypt file names too
• Cons: the recipient may need software to open it

That second point used to be a big deal. Recent versions of Windows 11 can now open 7z files natively, which helps. On macOS, people typically need a free app such as Keka or The Unarchiver.

RAR

RAR is a proprietary format. You need WinRAR (paid, with a famously endless trial) to create RAR files, though many tools can extract them.

• Pros: good compression, built-in recovery records that can repair minor corruption
• Cons: proprietary, and not much better than 7z for most uses

Unless you specifically need recovery records, there isn't a strong reason to pick RAR over 7z today.

The thing most people miss: some files don't compress

Compression works by finding patterns and repetition. Files that are already compressed have very little left to squeeze. That includes:

• JPEG, PNG, HEIC and WebP images
• MP4, MOV and most other video files
• MP3 and AAC audio
• PDFs with lots of images
• DOCX, XLSX and PPTX files, which are actually ZIP archives under the hood

Zipping a folder of 200 vacation photos might save you 1-3%. That's not a typo. The archive is still useful for bundling everything into one file, but don't expect it to get smaller.

On the other hand, these compress very well, often by 70-90%:

• Plain text, CSV files and logs
• Source code
• Uncompressed images like BMP or TIFF
• Database dumps

A note on password protection

If you're encrypting an archive, the format and settings matter:

• Classic ZIP encryption (often called ZipCrypto) is old and can be broken. Some tools still use it by default.
• ZIP with AES-256 is strong, but the built-in Windows and macOS extractors can't always open it, which confuses recipients.
• 7z with AES-256 is strong, and with "Encrypt file names" turned on, nobody can even see what's inside without the password.

If security matters, use 7z with AES-256 and send the password through a different channel than the file.

So which one?

• Sending to someone non-technical: ZIP. It opens with a double-click on any computer.
• Sending lots of text, code or data: 7z. The size savings are real.
• Sending something sensitive: 7z with AES-256 and encrypted file names.
• Sending photos or video: ZIP with no compression (the "store" setting) is fine. You're just bundling, not shrinking.

If you're not sure, use ZIP. A slightly larger file that opens on the first try beats a smaller one that leads to a "how do I open this?" email.