📖 What is an XLSB File?
An XLSB file is a Microsoft Excel spreadsheet saved in a binary form. The letters stand for Excel Binary Workbook, and the file uses the .xlsb extension. It holds the same things a normal Excel file does, sheets of cells, formulas, charts and formatting, but it stores them as compact binary data.
The reason this format exists is speed and size. By keeping its data in a binary layout rather than text, an XLSB file opens and saves faster and takes up less room on disk. That advantage grows with the size of the workbook, so the format is a favourite for very large spreadsheets.
Microsoft introduced XLSB with Excel 2007, alongside the more familiar XLSX. Most people save their work as XLSX, and reach for XLSB only when a workbook grows big and slow enough that the performance gain is worth it.
Key Characteristics
- An Excel spreadsheet, sheets of cells
- Binary storage, not XML text
- Smaller and faster, than XLSX
- Holds macros, unlike plain XLSX
Good to Know
- Excel 2007 onward, opens it natively
- Same features, as an XLSX workbook
- Less portable, outside Excel
- Harder to inspect, being binary
⚡ Quick Facts
| File Extension | .xlsb |
| Full Name | Excel Binary Workbook |
| Category | Spreadsheet |
| Storage | Binary records, BIFF12 |
| Developer | Microsoft |
| Introduced | Excel 2007 |
| MIME Type | application/vnd.ms-excel.sheet.binary.macroEnabled.12 |
| Holds Macros | Yes |
| Opened With | Excel, LibreOffice Calc |
| Related Extensions | .xlsx, .xls, .xlsm, .csv |
⚙️ Binary, Not XML
The whole difference between XLSB and the everyday XLSX comes down to how the data is written inside the file. That single choice shapes the speed, the size and the handling of both formats.
XLSX stores text
An XLSX file keeps its data as XML, a text layout that programs can read and even repair by hand. That openness costs size and speed.
XLSB stores binary
An XLSB file keeps the same data as binary records, which the computer reads directly. That makes it quick and small, but not something you can read by eye.
📂 How to Open an XLSB File
An XLSB file opens in the same programs you would use for any Excel spreadsheet. The most complete support is in Excel itself.
In Excel
Microsoft Excel 2007 and later opens an XLSB file directly, with every sheet, formula and chart intact.
Free alternatives
LibreOffice Calc opens XLSB files directly. Google Sheets and Excel for the web cannot, so you convert to XLSX first, then upload that.
Just to view it
To read the data without Excel, an online viewer shows the sheets in the browser with nothing to install.
🛠️ How to Create One
You do not need a special tool to make an XLSB file. Any workbook already open in Excel can be saved into the binary format.
Open your workbook
Start with the spreadsheet you want in Excel, whether it is a new one or an existing XLSX file.
Choose Save As
Go to File then Save As, and open the dropdown that lists the file types you can save into.
Pick the binary type
Select Excel Binary Workbook from the list and save. Your workbook is now stored as an XLSB file.
🔄 Converting to XLSX
Since XLSB is less portable, converting to the widely supported XLSX is common when you need to share a file or open it in another program.
To XLSX
For sharing and wide compatibility.
To CSV
For plain data other tools can read.
To PDF
For a fixed copy to send or print.
To ODS
For the open document spreadsheet format.
⚔️ XLSB vs XLSX and XLSM
These three Excel formats look almost the same in use, yet they differ underneath. Here is where XLSB stands next to its two closest cousins.
| Format | Storage | Speed and Size | Holds Macros |
|---|---|---|---|
| XLSB | Binary | ✓ fast, small | ✓ yes |
| XLSX | XML | ~ larger | ✗ no |
| XLSM | XML | ~ larger | ✓ yes |
In short, XLSX is the everyday choice, easy to share and inspect but larger. XLSM is the same XML format with macros switched on. XLSB stores everything in binary, which makes it the fastest and smallest of the three and lets it hold macros, at the cost of being harder to use outside Excel.
🎯 When to Use XLSB
The binary format is not the right pick for every file. It shines in some cases and gets in the way in others.
Good for
- Very large workbooks, slow to open
- Heavy calculations, many formulas
- Files with macros, you run often
- Saving disk space, on big reports
Less good for
- Sharing widely, with mixed software
- Other spreadsheet apps, that may struggle
- Inspecting the file, by hand
- Sensitive data, you want easy to audit
🛡️ A Note on Safety
An XLSB file is a normal spreadsheet in almost every case, and there is nothing risky about the format itself. The caution is the same as for any Excel file that can carry macros, which is simply to be careful with files from people you do not know.
When Excel opens such a file it usually shows a warning and keeps macros switched off until you allow them. Leaving that protection in place, and only enabling macros in files you trust, keeps you on the safe side.
🚀 Going Further
Two situations come up often with XLSB files, one for people who code and one for when a file will not open.
Reading it in Python
The pandas library reads an XLSB file with read_excel when you pass the pyxlsb engine. The usual openpyxl engine cannot handle the binary format, so pyxlsb is the piece that makes it work.
If it will not open
A message that Excel cannot open the file often means it is damaged. Excel's Open and Repair option, reached from the Open dialog, recovers many files, and LibreOffice can serve as a second opinion.
🔀 Related Formats
XLSB sits among the Excel and spreadsheet formats you meet alongside it.
.xlsx | The standard modern Excel workbook, stored as XML and the most widely shared. |
.xlsm | An XML Excel workbook with macros enabled, the XML counterpart to a binary XLSB. |
.xls | The older binary Excel format from before 2007, still seen in legacy files. |
.csv | A plain-text file of comma-separated values, holding data with no formatting. |
.ods | The open document spreadsheet, used by LibreOffice and other free suites. |
❓ Frequently Asked Questions
The natural choice is Microsoft Excel 2007 or later, which opens an XLSB file directly with every sheet and formula intact. A free desktop option is LibreOffice Calc, which opens the format directly. Google Sheets and Excel for the web need the file saved as XLSX first. To just read the data, an online viewer such as Univik's shows the sheets in a browser with nothing to install.
An XLSB file is a Microsoft Excel spreadsheet saved in a binary form rather than the XML used by XLSX. The name means Excel Binary Workbook. It holds the usual cells, formulas, charts and formatting, but stores them as compact binary data, which makes the file smaller and quicker to open and save. It is most useful for very large workbooks.
The core difference is how each stores its data. XLSX uses XML text, which is easy to share and inspect but makes larger, slower files. XLSB uses binary records, which are smaller and faster to open and save, and it can also hold macros. XLSX is the everyday format most people use, while XLSB is chosen mainly for big, heavy workbooks.
Yes, generally. Because an XLSB file stores its data in binary rather than XML text, Excel can read and write it more quickly, and the file is smaller on disk. The bigger and more formula-heavy the workbook, the more noticeable the gain, with large files often opening and saving several times faster than the same data in XLSX.
The simplest way is in Excel, by opening the XLSB file and using Save As to choose the Excel Workbook (XLSX) type. Without Excel, an online converter does the job. Univik's File Converter turns an XLSB file into XLSX in the browser, which is handy when you want to share the spreadsheet in the more widely supported format.
Yes. Unlike the default XLSX format, which cannot store macros, an XLSB file can hold them, much like an XLSM file does. This is one reason the binary format suits workbooks that automate tasks. It also means you should be cautious with an XLSB file from an unknown sender, since a macro inside could run code when the file is opened.
Yes. LibreOffice Calc, a free spreadsheet program, opens XLSB files directly. Google Sheets and Excel for the web cannot open them until you convert the file to XLSX first. For viewing only, an online viewer displays the sheets in a browser. These options let you read the data even without Microsoft Excel installed.
You would choose XLSB when a workbook is large enough that opening and saving in XLSX feels slow. The binary format makes the file smaller and faster, which helps with big data sets, heavy calculations and files you save often. It also keeps macros. For everyday small spreadsheets, XLSX is usually the better, more shareable choice.
Usually yes. Storing data as binary records rather than XML text produces a more compact file, and benchmarks often show an XLSB file noticeably smaller than the same workbook in XLSX. The saving is largest on big spreadsheets with lots of data. This smaller size is one of the main reasons people switch a heavy workbook to the binary format.
In almost every case it is an ordinary spreadsheet and perfectly safe. The one caution is that XLSB files can carry macros, so a malicious file from an unknown sender could run harmful code. Only open XLSB files from sources you trust, and let Excel keep macros disabled until you have confirmed the file is genuine and safe to use.
Microsoft Excel 2007 and later is the main program, opening XLSB files with full support. LibreOffice Calc opens them as well. Google Sheets and Excel for the web need the file converted to XLSX first. Online viewers, including Univik's, display the sheets in a browser without any software. For editing with everything intact, Excel remains the most reliable choice for the binary format.
XLSB stands for Excel Binary Workbook, sometimes written as Excel Spreadsheet Binary. The XLS part comes from Excel's long-standing spreadsheet extensions, and the B marks it as the binary version. The name captures exactly what the format is, a workbook that stores its contents as binary data rather than the XML text used by the XLSX format.
Not directly. Google Sheets and Excel for the web cannot open the binary format. The way around it is to first open the XLSB in Excel or LibreOffice Calc, save it as XLSX, then upload that XLSX to Google Drive and open it with Sheets. An online converter can also make the XLSX for you. This limitation trips up a lot of people who expect Sheets to handle it.
Use pandas with the pyxlsb engine, calling read_excel and passing engine set to pyxlsb. The default openpyxl engine does not support the binary format and will raise an error, which is a common stumbling block. Once pyxlsb is installed, reading an XLSB into a data frame works just like reading an XLSX, which makes the format handy for large data sets in Python.
A message that the file format or extension is not valid usually means the file is damaged or was not fully downloaded. Try Excel's Open and Repair, reached through the arrow beside the Open button in the Open dialog. Opening the file in LibreOffice can act as a second opinion, and checking for an earlier saved version sometimes recovers the data when a binary file will not open.
📝 Summary
An XLSB file is a Microsoft Excel spreadsheet saved in a binary workbook format, using the .xlsb extension, that stores cells, formulas and charts as compact binary records instead of the XML used by XLSX. This makes it smaller and faster to open and save, which is why it suits very large, formula-heavy workbooks, and it can hold macros. Excel 2007 and later opens it fully, LibreOffice Calc and Google Sheets handle it with some limits, and an online viewer shows the sheets in a browser. Converting to XLSX, CSV or PDF makes it easier to share. XLSB trades wide compatibility and easy inspection for speed and size, so most people keep everyday files as XLSX and use XLSB for the big ones.