Compress ZIP: help & limits

1. Choose an unencrypted ZIP.
2. Choose Compress ZIP to rebuild it with Deflate compression.
3. Review the measured size, then download the smaller ZIP or the retained original.

Examples

• Reduce a ZIP of uncompressed text logs before sending it.
• Check whether a ZIP of JPG photos can shrink; keep the original if it cannot.

Uses Deflate level 6, not an exhaustive smallest-size search. Already compressed files may not shrink. Rebuilt ZIPs preserve file bytes and folder paths but replace ZIP dates and discard comments, extra fields, and permissions. ZIP64, encryption, symbolic links, and legacy filename encodings are unsupported.

Processing stops after 60 seconds. Files and results are held in memory; even within these limits, a low-memory device may fail. Cancel and retry with fewer or smaller files.

Files, names, and extracted contents stay in browser memory. A local worker packages or expands bytes. Reset ends processing and releases file references; it does not securely erase device memory. File contents are not uploaded and there is no server fallback. Website and account traffic is separate from file processing. Downloads remain wherever you save them.

No. Photos, video, and compressed documents often have little space left to save. If the rebuilt ZIP is not smaller, you download the untouched original instead.

No. ZIP compression is lossless and does not change the files inside it. Use the image compressor separately when you want to change image encoding or quality.