File Compressor

The File Compressor bundles several files, or a whole folder, that you choose into a single ZIP archive, with an adjustable compression level. It is handy for combining a few documents, pictures or logs into one file for email, upload or archiving. It only makes ZIP files. It cannot set a password, does not produce 7z or RAR, and cannot open existing archives. If you need a password on a PDF, see the "PDF to Password-Protected ZIP" tool, which is limited to PDFs.

How to use it

1. Click the dashed area "Click to choose files (multiple, any type)" and select the files to bundle. You can click again to add more; new files go to the end of the list.
2. Or click "Or choose a whole folder (keeps folder structure)" and pick a folder. Every file inside it, including subfolders, is added to the list under its relative path (for example Photos/Trip/a.jpg), and the ZIP keeps the same directory layout. Files and folders can be mixed.
3. Each file is listed with its name and its size in KB. Click the X at the end of a row to remove a file you do not want.
4. Set the "Compression level" slider to a value from 1 to 9; the default is 6. Higher values squeeze harder and take longer, while lower values are faster but compress less.
5. Click "Compress to ZIP (N file(s), X KB)". The button shows the current file count and total size, and reads "Compressing…" while it works.
6. When it is done you will see "Done: X KB". Click "Download ZIP" to save compressed.zip. Compare that figure with the original total shown on the button.

A real run showing what the level does

To show how much the compression level really matters, we ran a local test with the same library the tool uses (JSZip). We built a text log of 2,000 repeated English sentences, 108,890 bytes in all. At levels 1, 6 and 9 the resulting ZIPs were 5,402, 5,306 and 5,244 bytes. On highly repetitive text like this, the three levels differ by only a few percent, and a higher level is only slightly smaller. In a second test we used 100,000 bytes of random data, which behaves like content that is already compressed. Even at level 9 the ZIP came out at 100,149 bytes, slightly larger than the input. So text files compress very well, while JPG, PNG, MP4 and existing archives barely shrink and can even grow a little. Your own files will give different numbers, so rely on the size the page reports.

Supported range and known limits

• The only output is ZIP (DEFLATE), always named compressed.zip. There is no password, no split archives, no 7z, RAR or tar.gz, and no extraction.
• The only setting is the 1 to 9 level slider. For files that are already compressed, such as images, video, audio and modern Office documents, raising the level does little.
• Files added with the file picker are placed flat at the root of the ZIP; files added with "Or choose a whole folder" keep their relative paths, starting with the chosen folder's name. Empty folders do not appear in the ZIP because the browser only supplies a list of files. The browser may show a confirmation prompt when you pick a folder, and some mobile browsers do not support folder selection.
• Adding or removing a file clears the previous ZIP result, so click the compress button again before downloading. Files with the same path are numbered automatically inside the ZIP (for example report (1).pdf) instead of overwriting each other.
• All files are processed in browser memory. With very many files or a very large total (hundreds of MB), the page may slow down or fail.
• There is no percentage-saved readout, only the compressed size, and no progress bar.

FAQ: Why did my files barely get smaller?

ZIP works by finding repeated content and describing it more compactly. Text, logs, code and CSV files are very repetitive and shrink a lot. JPG, PNG, MP4, MP3, many PDFs and modern Office documents are already compressed internally, so there is almost nothing left to remove, and the ZIP's own overhead can even make the result slightly bigger. This is a general property of compression and has nothing to do with how high you set the level.

FAQ: Which compression level should I pick?

The default of 6 is a balanced choice between speed and size and is fine for most uses. Choose 9 if you want the smallest result and do not mind waiting longer, or 1 to 3 if the files are large and you want it quickly. As the example above shows, the size difference between levels is usually small, so there is rarely a reason to keep experimenting.

FAQ: Can I put a password on the archive?

Not with this tool. It creates a normal, unencrypted ZIP that anyone can open. If you only need to protect a PDF, use the "PDF to Password-Protected ZIP" tool, which makes an archive that needs a password to extract (note that this is not encryption of the PDF itself).

FAQ: Will the ZIP open on phones and computers?

Yes. The output is a standard ZIP file that Windows, macOS, most phone file managers and common archive programs open directly. The only caveat is non-English file names: modern software handles them fine, but a few very old extraction tools may show garbled characters.

Privacy and how files are processed

Bundling happens entirely in your browser. The files you pick are read into memory, a compression library (JSZip) running in the page creates the ZIP, and the download is offered through a temporary local link. Nothing is uploaded to a server and no account is needed. Refreshing or closing the page clears the file list and the generated archive.