Compress Excel files without touching your data
Excel workbooks grow for reasons that have nothing to do with your numbers. Pictures pasted at full camera resolution, cached calculation data, preview thumbnails, and empty space left behind by years of edits all add up. This tool removes that dead weight from both modern .xlsx files and older .xls files, while every cell, formula, chart, and sheet stays exactly as it was.
Everything runs in your browser. Your spreadsheets are never uploaded, which matters for budgets, payroll, and customer data.
How to use it
- Choose one or more
.xlsx,.xlsm, or.xlsfiles, or drag them onto the box. - Leave the recommended settings, or adjust image size and quality.
- Check each result: size savings, the verification badge, and what was changed.
- Download the compressed workbook, or all of them as a ZIP.
What gets smaller in an XLSX file
An .xlsx file is a ZIP archive of XML files plus any images. The cell data is already compressed and rarely the problem. These are:
| Part | What happens | Effect on your workbook |
|---|---|---|
| Pictures and logos | Oversized photos are resized and re-saved as JPEG. Photos stored as PNG or BMP are converted. Logos and screenshots stay sharp, and transparency is kept. | Pictures look the same at normal zoom and stay where they were |
| Calculation chain | calcChain.xml, Excel's record of the order it last calculated formulas, is removed | None. Excel rebuilds it the next time it calculates. Formulas and values are unchanged. |
| Preview thumbnail | Removed | None. It's only used by file browsers. |
| Personal metadata (optional) | Author, last modified by, last printed date, company, and manager are removed | None on the data. Good before sharing outside your organization. |
The calculation chain can be surprisingly large. In big models with tens of thousands of formulas it often takes up hundreds of kilobytes or more.
Older XLS files
Files from Excel 97 through 2003 use a binary format stored in a Compound File, a small file system inside a single file. Every save can leave unused blocks behind. Compacting rebuilds the container with only the parts the workbook actually uses, copying every byte of your data exactly. The tool then reads the result back and confirms each internal part is identical to the original. You can also download a ZIP, which usually shrinks an .xls file much further for email or storage.
Converting to .xlsx is also worth considering: open the file in Excel and choose Save As. The modern format is compressed automatically and is often less than half the size.
How each file is checked
Excel is strict about the internal structure of a workbook. If a part is missing or mislabeled, it shows a repair prompt. So after compressing, the tool reopens its output and checks it the way Excel would: every internal link must point to a part that exists, every part must be declared with a content type, every checksum must match, and every edited XML file must be well-formed. The green Verified badge means all of those checks passed. Problems that were already present in the original aren't blamed on the compression. In testing, compressed workbooks opened with the same cell values in LibreOffice and in the openpyxl Python library.
Frequently asked questions
Will my formulas or values change?
No. Sheet data, formulas, formatting, charts, named ranges, and macros are never rewritten. Only images, the calculation cache, the thumbnail, and optional metadata are touched.
Are my files uploaded?
No. Workbooks are opened, compressed, and checked in your browser. Nothing is sent to a server.
Does it work with macro-enabled workbooks?
Yes. Macros in .xlsm and .xls files are copied exactly, unchanged.
What about password-protected workbooks?
Workbooks with an open password are encrypted and can't be changed without it. Remove the password in Excel, compress, then add it back. Sheet protection passwords (protecting cells from edits) don't get in the way.
Why did my file barely shrink?
If a workbook has no pictures and no large calculation cache, there's little to remove. That usually means it was already efficient. For an old .xls, the ZIP download or saving as .xlsx will help the most.
Why does Excel ask to save when I close the compressed file?
Excel rebuilds the calculation chain and thumbnail the first time it opens the file, so it considers the workbook changed. Saving is safe either way.