Large Excel files can become slow to open and save. They also consume significant disk space and are difficult to share via email. The standard .xlsx format is a compressed XML file, which can be inefficient for complex workbooks. This article explains how to save your files in the binary .xlsb format to make them smaller and faster.
Key Takeaways: Saving Excel Files as .xlsb
- File > Save As > Browse > Save as type: Change the file type from .xlsx to Excel Binary Workbook (.xlsb).
- Binary file structure: The .xlsb format stores data more efficiently than XML, leading to smaller file sizes and faster processing.
- Macro compatibility: The .xlsb format can contain VBA macros, unlike the standard .xlsx format which requires a separate .xlsm file.
What the Excel Binary Workbook (.xlsb) Format Does
The Excel Binary Workbook format, with the .xlsb file extension, is a compressed, non-XML file format. It is designed for maximum performance and minimum file size. While the default .xlsx format is a collection of XML files inside a ZIP container, the .xlsb format stores data in a proprietary binary structure. This binary structure is more compact, requiring less disk space and less processing power for Excel to read and write.
The primary benefit is speed. Opening, saving, and calculating in a .xlsb file is often noticeably faster, especially for workbooks with tens of thousands of rows, complex formulas, or extensive PivotTables. The secondary benefit is file size reduction. A .xlsb file can be 25% to 50% smaller than its .xlsx equivalent, making it easier to store and email.
Prerequisites for Using .xlsb
You need Excel 2007 or a later version to create or open .xlsb files. The format is fully supported in Excel for Microsoft 365, Excel 2021, Excel 2019, Excel 2016, and Excel 2013. Most features available in .xlsx files work identically in .xlsb, including tables, charts, slicers, and Power Query connections. If your workbook contains VBA macros, they will be preserved within the single .xlsb file.
Steps to Save an Excel File as .xlsb
Use this method to convert an existing .xlsx or .xlsm file to the binary format. The original file will remain unchanged.
- Open your workbook in Excel
Launch the Excel file you want to convert to the binary format. - Click File > Save As
This opens the backstage view where you manage file operations. - Click the Browse button
This opens the standard Save As dialog box on your computer. - Choose a save location
Navigate to the folder where you want to save the new .xlsb file. - Click the “Save as type” dropdown menu
A long list of file formats will appear. Scroll down to find the binary option. - Select “Excel Binary Workbook (*.xlsb)”
This sets the file format for your save operation. - Click the Save button
Excel creates a new .xlsb file in your chosen location. The original file remains open in Excel.
Setting .xlsb as the Default Save Format
If you frequently create binary workbooks, you can change Excel’s default save format.
- Go to File > Options
The Excel Options dialog box will open. - Select the Save category
This section controls how workbooks are saved. - Find the “Save files in this format” dropdown
It is located under the “Save workbooks” heading. - Choose “Excel Binary Workbook (*.xlsb)” from the list
This changes the default for all new workbooks. - Click OK
Your setting is saved. Now, when you press Ctrl+S on a new workbook, it will save as .xlsb by default.
Common Mistakes and Limitations of .xlsb
Other Users Cannot Open the File
If you send a .xlsb file to someone using Excel 2003 or earlier, they will not be able to open it. The binary format requires Excel 2007 or newer. Always confirm the recipient’s Excel version before sending. If compatibility is uncertain, use the older .xls format or the standard .xlsx format instead.
File Size Does Not Decrease Significantly
If your .xlsb file is not much smaller than the .xlsx version, the workbook likely contains many embedded objects like high-resolution images or large media files. The .xlsb format compresses worksheet data and formulas efficiently, but it does not recompress embedded images. To reduce size further, compress pictures via Picture Format > Compress Pictures before saving as .xlsb.
Third-Party Tools Cannot Parse the File
Some external data analysis tools, web applications, or automation scripts are built to read the open XML structure of .xlsx files. They may fail to read the proprietary binary .xlsb format. If your workflow depends on other software accessing the Excel file directly, test compatibility before switching to .xlsb.
.xlsx vs .xlsb vs .xlsm: Format Comparison
| Item | Excel Workbook (.xlsx) | Excel Binary Workbook (.xlsb) | Excel Macro-Enabled Workbook (.xlsm) |
|---|---|---|---|
| Primary use | Standard modern format, no macros | Maximum speed and minimum size | Standard format with VBA macros |
| File structure | ZIP container with XML files | Proprietary binary format | ZIP container with XML files |
| File size | Larger | Smallest | Larger |
| Open/Save speed | Standard | Fastest | Standard |
| Macro support | No | Yes | Yes |
| External tool compatibility | High | Low | High |
You can now create smaller, faster Excel files by using the .xlsb format. This is ideal for large internal reports, complex financial models, or any workbook where performance is a priority. For your next project, try saving a copy as .xlsb and compare the open time with your original file. Remember that you can use the F12 key to open the Save As dialog directly, bypassing the File menu.