ZIP Maker & Extractor

Compression works by finding repetition, which is why results vary so much by file type. Text, CSV, JSON, HTML and source code typically shrink by 60–90% because they repeat words and structure constantly. JPG, PNG, MP3, MP4 and PDF are already compressed internally, so zipping them usually saves a percent or two — that is expected, not a fault, and the archive is still useful for bundling many files into one. On security: the tool strips path components from every entry when repackaging, which blocks the “zip slip” attack where a crafted archive contains names like ../../ that write files outside the folder you extracted into.

ZIP uses the DEFLATE algorithm, which combines LZ77 back-references to repeated byte sequences with Huffman coding of the result. The space saved is 1 − (compressed size ÷ original size), expressed as a percentage.

Password-protected and encrypted archives cannot be opened, and archives using less common compression methods may be unreadable. Because everything is held in memory, very large archives can exhaust what the browser allows — this suits everyday files rather than multi-gigabyte backups. Extraction repackages the contents as a single flat ZIP for download rather than writing loose files to disk, since browsers cannot write folders directly.

Two text files totalling 6 KB with a lot of repetition compress to well under half their original size, while the same operation on a JPG saves almost nothing because the image is already compressed.

1. Choose whether to create an archive or open one.
2. Select your files, or the ZIP you want to open.
3. For creating, pick a compression level.
4. Download the result.

• Expecting photos or videos to shrink much — they are already compressed.
• Assuming a ZIP is secure; standard archives are not encrypted.
• Trying to open a password-protected archive here.
• Loading enormous files that exceed the browser’s memory.

This tool creates ZIP archives from files you select, or opens an existing ZIP to list and repackage what is inside. Everything happens in your browser using a bundled compression library, so files are never uploaded to a server.

Anyone who needs to bundle files for email or upload, or open a ZIP on a device without archive software.

• No upload, so confidential documents stay on your machine.
• Adjustable compression level, from store-only to maximum.
• Shows the real compression achieved rather than a vague promise.
• Handles duplicate filenames instead of silently overwriting one.

• Bundling several attachments into one file for email.
• Checking what is inside a ZIP before extracting it.
• Compressing logs, CSVs or source files for transfer.
• Opening an archive on a machine with no archive software installed.