Excel 2007/2010 offers an option to save my files in an "Excel Binary Workbook" format that seems to be smaller (50% of the size in some cases) and load more quickly. Is there a downside to this format? Should I be avoiding it for some reason?

I'm thinking there has to be some shortcoming to it, or it would be the default save format instead of XLSX, but I can't figure out what the faults might be. XLSX seems to be reasonably common in other products that can import Excel files, but none of them support XLSB - why not?

4 Answers 4


As stated, xlsb is a binary file type, and saves in binary format. All other xls file types save in open XML format. We're not here to talk about advantages, but disadvantages.

  1. The only real disadvantage is going to be compatibility in using the data with software that wants XML instead of binary (web server for instance). If you link a lot of systems together, this may cause a problem with one of the layers, as XML was developed specifically for this purpose.

  2. Overall, there are no other disadvantages other than the fact that you might not be able to tell if there are macros in it or not as there is no macro-free version of this format. You can just change your macro settings to disable with prompt and examine visual basic to determine if there are harmful macros.

A compelling list to use xlsb as your default file format.

  • I suspected this was the case, but wanted to make sure. From other reading I've done, XLSX appears to be a more open standard, where XLSB is really just the next iteration of the XLS format - proprietary to Microsoft Excel and designed for speed/size, not compatibility. Thanks for your confirmation!
    – SqlRyan
    Feb 16, 2012 at 20:02
  • I know this answer is a little dated, but it's incorrect/inaccurate. "Classic" .xls is of course an OLE Compound Document and not XML.
    – Daniel B
    Feb 27, 2014 at 22:34
  • In 2007 and 10? Feb 28, 2014 at 2:08
  • XLSB files support macros, which might result in mail servers blocking them by default.. In addition, the OOXML formats (XLSX and XLSM) are standardised, which can result in greater compatibility with other applications. Jun 6, 2017 at 15:00

Mac iWork Numbers, Quickview, iOS preview and iOS Numbers do not recognise xlsb files.

  • Thanks for letting me know - I suppose if third-party software is going to allow the import of Excel files, they won't implement two different formats, and will likely only support XLSX, as that's the more "Standards-based" one.
    – SqlRyan
    Feb 10, 2013 at 20:23

Saving in binary allows formulas to be saved properly if they are longer than the 8192 character limit.


I don't use the xlsb format for two reasons.

  1. Because the file has all of the XML plus the binary, the file is larger than the corresponding xlsx or xlsm file.

  2. When I was working with a large and complex file, the binary would get corrupted frequently and I would have to restore from a back up copy of the file.

Update: I tried the xlsb format when it first came out and had the above problems. Problem 1 doesn't happen with Excel 2010 so maybe problem 2 is fixed also.

On the other hand, even if all of the above is fixed, I still won't use xlsb very often because most of my Excel files are actually VBA projects. Tracking a binary in a code repository will bloat the repository pretty quickly. (I use Mercurial for my code repository and, with the zipdoc extension turned on, I can tell it that xlsx AND xlsm files are zipped XML text files instead of binary.)

  • 1
    Every time I've used xlsb files, they've been significantly smaller than the same file as an xlsx.
    – afrazier
    Feb 22, 2012 at 0:06
  • @afrazier, Thanks for letting me know! I need to remember to double-check tech stuff when my knowledge is over 3 years old.
    – mischab1
    Feb 22, 2012 at 22:31
  • 2
    Just for reference here, I've been using XLSB almost exclusively since posting this question a year ago, will no ill effects - no corrupted data or files, and in addition to be smaller, they load in about half the time.
    – SqlRyan
    Feb 10, 2013 at 20:24
  • I have been careful about using xlsb, as it is supposed to get corrupted more often, but actually opening corrupted xlsm files by repair and saving them as xlsb fixed the file (actually supressed errors, as converting back to xlsm will "corrupt" the file) a few times for me. It is especially a good fix in the following cases: 1. Printer error when opening file. 2. You have manually deleted some part of Excel file, after changing extension to .zip and unpacking. Xlsm will yell about loss of integrity, xlsb will just assume that everything is fine. Apr 8, 2017 at 18:30

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