Microsoft Excel .xls and .xlsx weirdness

This entry was published at least two years ago (originally posted on January 26, 2010). Since that time the information may have become outdated or my beliefs may have changed (in general, assume a more open and liberal current viewpoint). A fuller disclaimer is available.

I’ve been attempting to troubleshoot some issues with sending Excel files back and forth between my Mac at home and a professor who uses a Mac at home and a Windows PC at school. Even though we’re both using current versions of Excel, and though the files opened fine on her Mac, she was having consistent problems on the Windows machine.

After a few days of back-and-forth and trying to narrow things down, here’s what I’ve come up with.

For some reason, though Excel:mac2008 (hey, that’s how the ‘About’ screen writes the product name, don’t blame me) uses the new XML-based file structure, when saving files, it uses the old standard .xls file extension. Oddly, at least on my machine, it is behaving like this even though Preferences… > Compatibility > Transition > Save files in this format: is set to “Excel Workbook (.xlsx)”.

(And as an aside, why must there be an open workbook to access Excel’s preferences dialog box?)

Current versions of Excel on the Windows side of the fence, however, use (and expect) the .xlsx extension. Same file types, but different extensions, and this causes confusion. When Excel (Windows) sees the .xls extension, it expects a different type of data than it does when opening a document with the .xlsx extension, and it chokes when attempting to open the file.

The solution? Manually change the extension to .xlsx before e-mailing the file.


3 thoughts on “Microsoft Excel .xls and .xlsx weirdness”

  1. FYI

    Info Regarding File Extension Xlsx

    Microsoft has stated several benefits to using the new .xlsx format including reduced file size, increased security, improved interoperability between Office products, and better file recovery technology. In terms of the file size issue, it is reported that the new .xlsx file can be up to 75% smaller than previous .xls files. Excel automatically compresses the .xlsx file (using ZIP compression) when the file is saved, and uncompresses it when it is re-opened. The compression allows for easier and quicker transfer of files between computers or over a network.

    The .xlsx format is essentially a container but Microsoft has introduced new terminology to reflect its new open formats. Instead of calling their structure a container, they have chosen the word “package”. Inside the package are three groups of “parts”. The first group contains three individual parts that store information about document properties, application properties, and customized document properties. The second group contains the data for the individual worksheets, while the third group stores information about styles, charts, and strings. The third group of parts is stored relationally to each individual worksheet.

    Errors with .xlsx files are the same as one would expect from any data file. Corrupt data can cause Excel to not display the worksheets correctly, it might not load the document at all, or it could cause a software crash. Corrupt data in an .xlsx file is unlikely to cause any significant damage to the operating system. The most common error with these files is caused when importing the documents into non-Microsoft spreadsheet applications. Though many other packages claim support for the .xlsx file, the conversion in most cases does not go perfectly. In some cases users will get an “unable to open” error. Individuals should check with their software developer to see if there are any updates or bug fixes to address the problem.

    Windows users have the most options for programs that open .xlsx files including Microsoft Excel 2007, Excel 2000, XP, and 2003 (with converters installed), OxygenOffice Professional, Calc, and Panergy docXConverter. Mac Users can choose from Microsoft Excel 2008, Apple Numbers, Calc, and Panergy docXConverter. For Linux systems there is OxygenOffice Professional and Calc.

    Other third party conversion programs are available such as Batch XLS and XLSX Converter. This program does just what its name implies; it allows for batch conversion of dozens of file formats including .xls and .xlsx. The program is Windows only, for XP, 2000, 98, and ME. Another Windows only conversion program is Convert XLS from Softinterface, Inc. Users who prefer an on-line conversion service can try Zamzar or SheetConvert.


  2. good job woodymax.

    so were you paid to put that cut-and-paste comment up, or did you just steal it?

    I’m curious, because you are either a shill or a thief.

    I just read the same thing, almost word for word, posted before your comment’s time-stamp, on another site. If you are using someone else’s writing, then give them credit, even when its technical writing. Otherwise it’s intellectual theft.

  3. Dear “woodymax, shill or thief”,

    It isn’t intellectual theft, really speaking, it is free information anyone can use. Is Woodymax profiting from this? It is a comment on an article on a website he does not own.

    I will now paste lyrics from a song, which you may deem a crime because I copy and paste it from one of 100’s of lyrics site:

    “Oh, the shark has pretty teeth, dear
    And he shows ’em, pearly white
    Just a jack knife has Macheath, dear
    And he keeps it, keeps it way out of sight”

    Please don’t sue me(!)

    Some people need to chill out.

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