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.XLSB file extension

To open .XLSB files on Windows, open Microsoft Excel (Office 2007 or later).

Open a .xlsb file with Microsoft Excel (Office 2007 or later). In Excel, use File > Open and select the .xlsb workbook, or double-click it if Excel is set as the default app.

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Last updated: June 12, 2026

Open on your device

Choose your operating system for a dedicated step-by-step opening guide.

How to open .XLSB files

Use these platform-specific instructions to open .XLSB files safely.

Windows

  1. Open Microsoft Excel (Office 2007 or later).
  2. Go to File > Open, browse to the .xlsb file, and open it (or double-click the file if Excel is the default).
Full Windows guide

Mac

  1. Open Microsoft Excel for Mac.
  2. Use File > Open and select the .xlsb file.
Full Mac guide

Linux

  1. .xlsb is an Excel-specific binary workbook format; if you cannot open it in your Linux office suite, transfer the file to a system with Microsoft Excel (Office 2007 or later) and open it there.
Full Linux guide

iOS

  1. If you have access to Microsoft Excel on a desktop (Office 2007 or later), open the .xlsb there; if a mobile app cannot open it reliably, convert it in Excel to .xlsx for easier sharing.
Full iOS guide

Android

  1. If the file does not open correctly on mobile, open it in Microsoft Excel on a desktop (Office 2007 or later) and save a copy as .xlsx for broader compatibility.
Full Android guide

Security notes

  • .xlsb is a binary Excel workbook format; treat unexpected .xlsb attachments as potentially risky content because spreadsheet files can be used as a delivery vehicle in social engineering scenarios.
  • Because the format is binary (BIFF12), it is harder to inspect manually than XML-based .xlsx; prefer opening untrusted files in a controlled environment and validate the sender before enabling any interactive content.
  • The format is formally specified by Microsoft ([MS-XLSB]); keep Excel updated to benefit from security fixes in file parsing.

Macros, scripts, and embedded content

PDF, Office, and some rich e-book containers may include macros, JavaScript actions, or external links. Phishing campaigns abuse that. Keep your viewer suite patched, avoid enabling macros on unexpected documents, and treat “urgent” invoices or parcel notices as untrusted until verified.

Avast

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Norton

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Can't open this file?

These are the most common causes and fixes when .XLSB files fail to open.

Common reasons

  • Workbook won’t open or shows as an unsupported format
  • File is large or slow; need a smaller version for sharing
  • Automation/macro safety concerns

Fix steps

  1. Open the file in Microsoft Excel (Office 2007 or later).
  2. If you need to use another program, open it in Excel first and save a copy as .xlsx.

OS-specific troubleshooting

What is a .XLSB file?

.xlsb is an Excel workbook stored in a binary file format (BIFF12) defined by Microsoft’s [MS-XLSB] specification. Unlike .xlsx (ZIP + XML), .xlsb stores workbook parts in a binary structure, which can make large spreadsheets smaller and sometimes faster to load/save in Excel.

Background

Excel Binary Workbook (.xlsb) was introduced with Microsoft Office 2007 as part of the Office Open XML era, but it uses a binary representation rather than the XML-in-ZIP approach used by .xlsx. The Library of Congress format description notes it as an Excel binary workbook format introduced with Office 2007 and points to the MS-XLSB specification for technical details.

Common MIME types: application/vnd.ms-excel.sheet.binary.macroEnabled.12

Further reading

Authoritative resources for more details on the .XLSB format.

Common .XLSB issues

Workbook won’t open or shows as an unsupported format

.xlsb is the Excel Binary Workbook (BIFF12) format and is supported in Excel, but older Excel versions or non-Excel tools may not fully support it.

  1. Open the file in Microsoft Excel (Office 2007 or later).
  2. If you need to use another program, open it in Excel first and save a copy as .xlsx.

File is large or slow; need a smaller version for sharing

Large workbooks can be bulky in some formats. Microsoft explicitly suggests saving as .xlsb as one approach to reduce Excel file size.

  1. In Excel, use File > Save As.
  2. Choose “Excel Binary Workbook (*.xlsb)” to create a smaller copy.

Automation/macro safety concerns

.xlsb files are workbooks and can be used in environments where macro-enabled content exists; users may treat them similarly to other Excel files when assessing trust and origin.

  1. Only open .xlsb files from trusted sources, especially if you were not expecting the workbook.
  2. If you must share with others who have stricter policies, consider saving an .xlsx copy without any active content you don’t intend to distribute.

FAQ

What program opens .xlsb files?

Microsoft Excel (Office 2007 and later) opens and saves .xlsb (Excel Binary Workbook / BIFF12).

Why would I use .xlsb instead of .xlsx?

.xlsb stores the workbook in a binary format and is commonly used to reduce file size and improve performance for large workbooks; Microsoft lists it as an option when reducing Excel file size.

Is .xlsb the same as the old .xls format?

No. .xlsb is the Office 2007-era Excel Binary Workbook format (BIFF12) defined by the MS-XLSB specification; it is distinct from older .xls formats.

What is the official MIME type for .xlsb?

IANA lists application/vnd.ms-excel.sheet.binary.macroEnabled.12 for Excel binary workbooks (.xlsb).

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