# Microsoft Office Application Help - Excel Help forum > Excel General >  > [SOLVED] .xlsb vs .xlsx

## yamalady

Can someone explain the difference between .xlsb and .xlsx?  I use .xlsb for all my files, but that was because it was suggested by my IT department so I can upload my large files to Sharepoint.  It will dramatically reduce the size of my files...which is beautiful!  But I would like to understand the difference because I am trying to get others in my office to follow me in using .xlsb.  But the argument is, "then why didn't Microsoft make it their default?".  Can you help me explain?

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## mike7952

Hello

They're all similar in that they're essentially zip files containing the actual file components. You can see the contents just by replacing the extension with .zip and opening them up. The difference with xlsb seems to be that the components are not XML-based but are in a binary format: supposedly this is beneficial when working with large files.

xlsx loads 4 times longer than .xlsb and saves 2 times slower and has 1.5 times a bigger file. Tested on a generated worksheet with 10'000 rows * 1'000 columns = 10'000'000 (10^7) cells of simple chained =…+1 formulas

both formats support exactly the same feature set

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## Kyle123

xlsb is a binary file format, it is very fast and dramatically reduces file size as you have found out. It does have limitations however though these may well not impact you, firstly it cannot support macros, only xlsm can and secondly it cannot be read by other software. Excel has long been used as an input format for various applications, these won't be able to read xlsb. You could however save your xlsb as xlsx/xls if this is an issue though.

I always use xlsb unless there is a specific reason why I can't, in my case usually macros

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## mike7952

@Kyle123,

I believe xlsb will support macros. Test it and See.

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## yamalady

You guys are wonderful!!  Thank you both!

---------- Post added at 08:40 AM ---------- Previous post was at 08:35 AM ----------

Kyle,  I just tested using a macro in an .xlsb file.  It did support it.

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## Kyle123

Ah right, fair enough  :Wink:  Shows how much I actually use excel these days (not a lot).

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## yamalady

You are both great.  Thanks again!

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## Cutter

@ yamalady

Based on your last post it seems that you are satisfied with the solution(s) you've received but you haven't marked your thread as SOLVED.  I'll do that for you now but please keep in mind for your future threads that Rule #9 requires you to do that yourself.  If your problem has not been solved you can use Thread Tools (located above your first post) and choose "Mark this thread as unsolved".
Thanks.

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