What This Tool Does
This tool re-compresses an existing ZIP file: every entry is read out and written back into a fresh archive. The purpose is to recover space when the original ZIP was packed with weak or no compression, or to normalize an archive built by a tool that stored files without compressing them.
The result includes an honest report of the original size, the new size, and the bytes saved. The tool will say plainly when re-compression did not help instead of presenting a fake improvement.
How It Works
Each entry inside the ZIP is decompressed from the source archive and compressed again into the output archive using DEFLATE at the level you choose. The output is reopened and its size compared against the original to produce the report.
Step by Step
- 1
Upload a ZIP file.
- 2
Choose the compression level.
- 3
Click Re-Compress ZIP.
- 4
Review the size report and download the optimized archive.
When It Helps
- ZIPs created with stored (no compression) entries shrink a lot when re-compressed.
- Text-heavy archives can gain from the maximum level.
- Already tight ZIPs may not shrink at all; the report will say so.
Troubleshooting
- Only real ZIP archives can be re-compressed; other formats are rejected.
- Corrupted entries cause an explicit failure rather than a partial output.
- Encrypted ZIPs cannot be re-compressed without the password.