How to create a ZIP file
- Drop files onto the drop zone above, or click to choose them. To include a whole directory, drag the folder in or use Add a folder; the folder structure is kept inside the archive.
- Type an Archive name. It starts as
archive, and the.zipextension is added for you. - Pick a Compression level: Store (no compression), Fastest, Normal or Maximum.
- Optionally enter a Password (optional). When a password is given, every file is encrypted with AES-256.
- Click Create ZIP, then use the Download button next to the finished archive.
The archive is built by zip.js inside your browser tab. Neither your files nor your password leave the device.
Choosing a compression level
ZIP archives normally use the Deflate algorithm, which looks for repeated byte sequences and replaces them with short references. The four options map to Deflate levels 0, 1, 6 and 9. Higher levels search harder for repeats, so they spend more CPU time to gain a few extra percent.
| Option | Deflate level | Good choice when |
|---|---|---|
| Store (no compression) | 0 | The files are photos, videos or other already-compressed data and you just want one bundle quickly |
| Fastest | 1 | You are packing a large amount of data and speed matters more than the last few megabytes |
| Normal | 6 | Everyday use; the usual balance between speed and size |
| Maximum | 9 | Text-heavy content such as logs, CSV exports, source code or HTML where every byte counts |
How much a file shrinks depends far more on what it contains than on the level you choose. Plain text, spreadsheets saved as CSV and uncompressed formats like BMP or WAV are full of repetition and often shrink dramatically. JPG, PNG, MP4, MP3 and modern Office documents (.docx, .xlsx and .pptx are themselves ZIP containers) are already compressed, so Deflate finds almost nothing left to remove. Zipping a folder of holiday photos at Maximum will take longer than at Store and save very little space. A ZIP still bundles them neatly, but it will not make them smaller.
What ends up in the archive
- Each file keeps its original modification date, so the dates you see after extracting match the originals.
- Empty folders are not stored. A folder only appears in the ZIP if it contains at least one file.
- If two files would end up at the same path, the later one is renamed with " (2)", " (3)" and so on, so nothing is silently overwritten.
- Everything is held in browser memory while the ZIP is written. Inputs above roughly 700 MB become slow, and more than 2 GB in total is refused.
Tips
- Bundling photos to email? Reduce their size first with Compress Image, since zipping JPGs gains almost nothing.
- If the finished ZIP is too big for an attachment limit, cut it into standalone pieces with Split ZIP.
- Need a stronger ratio for text and code? Create 7Z uses LZMA, which usually beats Deflate, though the recipient needs a tool that opens 7Z files.
- Use the password generator to make a long, random password for an encrypted archive.
Frequently asked questions
Why is my ZIP almost the same size as the original files?
The files were probably already compressed, for example JPG photos, MP4 videos or PDF scans. Deflate cannot shrink data that has no remaining repetition, whichever level you pick.
Can I zip a folder with subfolders?
Yes. Drag the folder onto the drop zone or click Add a folder. Subfolders that contain files are recreated inside the ZIP; empty ones are skipped.
How secure is the password option?
It uses AES-256, the strongest encryption the ZIP format offers. The file names and sizes inside the archive remain visible to anyone who opens the listing, though, so do not rely on encryption to hide what the files are called.
Is there a size limit?
The practical limit is your browser's memory. Up to a few hundred megabytes works smoothly; the tool refuses inputs larger than 2 GB.