Skip to content

Compress XLS files

Options for old Excel 97–2003 workbooks: a compressed ZIP or conversion to XLSX.

Drop files here

or

Choose files

XLS · PDF · DOC · DOCX · XLSX · PPT · PPTX

Files never leave your device

Loading the compressor…

How to compress XLS files

  1. Add your files

    Drop files on the box, paste them or choose them from your device. Nothing is uploaded.

  2. Check the settings

    The default preset suits most files. Change quality, size or format if you need a smaller file.

  3. Download the result

    Save each file or all of them as one ZIP. If a file cannot get smaller, you keep the original.

The binary XLS format

XLS is the workbook format of Excel 97 to Excel 2003. Its internal format is called BIFF8 (Binary Interchange File Format), a stream of binary records for cells, formulas, formats and charts, stored inside a Compound File Binary container like the old Word and PowerPoint files. Excel 2007 introduced XLSX as the new default, but XLS files remain common: exports from accounting systems, banks and ERP software, government statistics, templates that have been copied for years, and archives.

The format has fixed limits that often surprise people today. A worksheet holds at most 65,536 rows and 256 columns (up to column IV). Data beyond that is cut off when you save as XLS, which is one reason exports with large datasets look incomplete.

Why XLS files are often bloated

  • No internal compression. Every record is stored as is. The same data saved as XLSX, which is a ZIP archive, is usually much smaller.
  • Program-generated files. Many reporting tools write a separate format record for every single cell, or fill thousands of empty but formatted rows.
  • Accumulated history. Workbooks edited for years keep deleted styles, hidden sheets, old names and remnants that newer Excel versions clean up when saving to XLSX.
  • Embedded pictures and OLE objects, such as logos stored as uncompressed bitmaps.

What the tool offers for XLS

Rewriting BIFF records in a browser is too risky: a damaged workbook may still open but show wrong numbers, which is the worst possible outcome for a spreadsheet. The tool therefore leaves the XLS itself unchanged and gives you two choices:

  1. A compressed ZIP of the original. Binary spreadsheets are full of repetitive records, so XLS files usually compress very well in a ZIP. The recipient extracts the file and gets the identical workbook, which is ideal when the original format must be preserved, for example for a system import.
  2. Convert to XLSX, then compress. Open the file in Excel and choose File › Save As › Excel Workbook (.xlsx), or open it in LibreOffice Calc or Google Sheets and download as XLSX. The conversion alone usually makes it much smaller, and the Excel compressor can then shrink any pictures inside.

Before you convert an XLS

  • Macros. An XLS with VBA macros must be saved as .xlsm; a plain XLSX cannot hold them, and Excel warns you before discarding them.
  • Systems that expect XLS. Some older import routines in banking or accounting software accept only XLS. Use the ZIP option or ask whether XLSX is accepted.
  • Formulas and links. Links to other XLS workbooks keep their old file names. Update them if you convert the linked files too.
  • Check the compatibility report. Excel's Compatibility Checker lists features that behave differently; for ordinary tables there are none.

XLS questions

Why does the tool not compress my XLS directly?

The binary format cannot be rebuilt safely in a browser, and with spreadsheets even a small error can change values. Zipping or converting keeps your data exactly as it is.

Will converting XLS to XLSX change my numbers?

No. Values and formulas are carried over. Number formats and charts may look slightly different in rare cases, so review complex workbooks after converting.

My XLS export is cut off at row 65,536. Why?

That is the row limit of the XLS format. Ask the system for an XLSX or CSV export, which can hold over a million rows.

Can the recipient open a zipped XLS on a phone?

Yes. The file apps on iPhone and Android extract ZIP archives, and the Excel and Google Sheets apps open XLS files.

Related pages

For the old Word and PowerPoint formats, see DOC and PPT. The document compressor page lists every document tool, and how it works explains the privacy model.