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SLK XLSB
File conversion

Convert SLK to XLSB

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Verified by Adam B.· reviewed by FE Editorial ·updated Jun 25, 2026
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Is it possible to convert SLK to XLSB?
Yes - SLK converts to XLSB.

You can do it right here with our free converter - no sign-up, and your file is deleted right after.

The most reliable path is Microsoft Excel: open your .slk file, go to File > Save As, and choose Excel Binary Workbook (.xlsb). You can also use our free converter above - uploaded files are deleted after converting. The main caveat is that .xlsb is Excel-proprietary, so complex features are best preserved when Excel itself does the saving.

5 programs
Also to XLSB: XLSM · XLAM

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Tested on macOS, Windows & Linux
Last verified Sep 2026

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SLK → XLSB converterFREE
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Why convert SLK to XLSB?

SLK (SYLK) is a legacy text-based format with very limited feature support, while .XLSB stores spreadsheet data in a compact binary form that opens faster and produces smaller files than .xlsx. Converting is common when replacing old SYLK exports from databases or legacy systems with a full-featured Excel workbook. XLSB is especially practical for large datasets where load speed and file size matter.

How to convert SLK to XLSB

Microsoft Excel - File > Save As BUILT-IN

Open the .slk in Excel, go to File > Save As, and pick Excel Binary Workbook (*.xlsb) from the format dropdown - works on both Windows and macOS.

LibreOffice Calc FREE

Open the .slk in LibreOffice Calc, use File > Save As, and choose Excel Binary Workbook (.xlsb); XLSB write support is basic and some formatting may not transfer perfectly.

Command line - LibreOffice CLI

Convert in one step: libreoffice --headless --convert-to xlsb file.slk

Programs that convert SLK

Microsoft Excel
Microsoft Excel for Mac
Microsoft Office Mobile
LibreOffice Calc
Apache OpenOffice Calc (OpenOffice.org Calc)

About these formats

.SLK Symbolic Link (SYLK) Spreadsheet File

An SLK file is a SYLK (Symbolic Link) spreadsheet - a plain-text format Microsoft created for Multiplan in the early 1980s to move cell data, formulas, and basic formatting between…

Open .SLK details →
.XLSB Microsoft Excel Binary Workbook

An XLSB file is a Microsoft Excel workbook saved in binary format instead of the usual XLSX. It holds the same spreadsheets and can contain macros, but opens and saves faster for large…

Open .XLSB details →

Quality & what to watch

  • Formulas in the .slk source carry over as live formulas in the .xlsb output, not as static values.
  • SYLK files typically contain a single worksheet, so the resulting .xlsb will have one sheet unless you add more before saving.
  • .xlsb is Excel-proprietary - if broad compatibility matters, save to .xlsx instead, which LibreOffice and Google Sheets handle more fully.

Frequently asked questions

Can I convert SLK to XLSB without Microsoft Excel?
Yes - our free converter and LibreOffice Calc can both output .xlsb, though Microsoft Excel produces the most complete result.
Will formulas in my SLK file still work after converting?
Yes. SYLK encodes formulas as text and they are re-parsed as live formulas in the .xlsb output.
Is XLSB smaller than XLSX for the same data?
Generally yes - .xlsb uses a compact binary representation that is more space-efficient than the XML layers inside a .xlsx container, especially for large workbooks.
What formatting is lost when converting from SLK?
SYLK only stores basic cell and column formatting; anything beyond that - charts, images, conditional formatting - was already absent in the .slk source and will not appear in the .xlsb either.