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7z vs ZIP: which compression format should you use?

ZIP is everywhere. 7z compresses harder. Here's how the two formats actually stack up on ratio, speed, and compatibility — and when it's worth converting one to the other.

Compression ratio

7z, powered by the LZMA2 algorithm, typically produces archives 30–50% smaller than ZIP (Deflate) on the same input — especially on text, source code, and uncompressed binaries. ZIP wins essentially nothing on ratio; its appeal is universality, not density.

Speed

ZIP is faster to create and extract because Deflate is computationally cheap. 7z at default settings is slower to compress (LZMA2 trades CPU for size) but extraction is comparable. For one-off transfers where bandwidth is the bottleneck, 7z wins. For frequent read/write cycles, ZIP is friendlier.

Compatibility

• ZIP opens natively on Windows, macOS, iOS, Android, and every Linux distro. Zero setup.
• 7z needs 7-Zip on Windows, Keka or The Unarchiver on macOS, p7zip on Linux. Most users don't have it installed.

If you're sending an archive to someone non-technical, ZIP is the safer default. For your own backups or developer-to-developer transfers, 7z is usually worth it.

Encryption

7z supports AES-256 encryption of both contents and filenames. ZIP's legacy encryption is weak; modern ZIP variants offer AES too, but support across tools is inconsistent. For actual privacy, 7z is the better pick.

When to convert

Convert 7z → ZIP when sharing with someone who can't install extra software. Convert ZIP → 7z when you want a smaller archive for storage or upload. FileWhirl does both in the browser using the same p7zip engine the desktop tools use — files stay on-device and auto-delete after 1 hour.

• Convert 7z to ZIP
• Convert ZIP to 7z

TL;DR

Pick ZIP for compatibility and speed. Pick 7z when ratio or encryption matter more than universal support.