XLS or XLSX file ?

Since Excel 2007, you can save your Excel file with the extension xlsX. What the last X means ?

XLSX, What means the last X?

XML is a computer language. It means eXtensible Markup Language. In fact it's a language where all the data are ordered. No easy to understand for human but for a computer, when data are ordered it's easier to store.

Protection against macros

We have seen that the last x of a xlsx file indicates that the file is compressed and respects the XML standard. The M, of a xlsm file, indicates that the file contains macros.

A macro is a program written by an end-user to provide an automation (opening files, data comparison, data aggregation across multiple sheets, ...) but also a program may cause malfunctions. In addition, a macro can run directly when you open an Excel file, without prompting the user.

With an xls file, you don't know whether your workbook contains macros or not.

xlsX workbooks have no macro.

.xlsM extension has macro.

Extension of the working area.

In a Xls workbook, the row limit is 65,536 (216) and 256 columns (28) which corresponds to the column IV.

Now with xlsx workbooks (and xlsm), limits are 1,048,576 rows (220) and 16,384 columns (214) or the column XFD.

XLSX is a compress file

If you have on your computer an xls file and you save it in xlsx, you will see that the size has been significantly reduced.

The XML code compress your file. Have a look at this tip.

If you change the extension xlsx to zip, you can still open your file in a Text editor.

But be careful ! If you edit the xml files, you may destroy the architecture of the XML file and you will no longer be able to open your Excel file (after renaming the file zip file xlsx).


Other benefits of an XLSX file?

A lot of tools are online available only with a file xlsx

  • The Table
  • Embed file in a website (like all the exercises in this blog)
  • Themes for color or font

Related posts

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1 comment

    • Dick on 23/02/2018 at 17:55
    • Reply

    The draw back to .xlsx & .xlsm is that they (xlsx & xlsm) take as much as 3 times longer (in time) to open.
    I made a file and saved it down as .xlsx. Then I saved down the same file as .xls. Agreed, the .xls file shows that it's much larger, but it only took 4 seconds to open as to where the .xlsx file took about 18 seconds to open. I'm not ready to get rid of my .xls files because of this.

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