How to Reduce Zip File Size

Zip compression works by finding repeating patterns in data. Some file types compress very well, while others barely shrink:

Most zip tools default to "Normal" compression. Switching to maximum can squeeze out extra savings.

In 7-Zip's "Add to archive" dialog, set Compression level to "Ultra" and Compression method to "Deflate64" for best zip compatibility, or switch to 7z format with LZMA2 for maximum compression.

Since zip can't shrink already-compressed files much, reduce file sizes before zipping:

• Images: Convert PNG to JPEG (if transparency isn't needed), or use tools like TinyPNG to optimize. Reduce resolution if full-size isn't needed.
• Videos: Convert to H.265/HEVC or use HandBrake to reduce bitrate.
• PDFs: Use "Reduce File Size" in Adobe Acrobat, or an online PDF compressor.
• Documents: Remove embedded high-res images, or compress images within the document.

Before creating the archive, clean up:

• Delete temporary files (.tmp, .bak, ~$ files)
• Remove node_modules, .git, and other development folders
• Clear browser caches and thumbnails
• Use file deduplication to find and remove duplicates
• On Mac, exclude .DS_Store files: zip -r archive.zip folder/ -x "*.DS_Store"

The .7z format typically achieves 10-30% better compression than .zip thanks to its LZMA2 algorithm. The trade-off is that recipients need 7-Zip or a compatible tool to open it.

If your zip is too large for email (over 25 MB), you can split it into smaller parts:

This creates files like archive.zip, archive.z01, archive.z02, etc. Send each part separately, and the recipient can extract by opening the first file.

For more on this topic, see our guide to emailing zip files.