XML vs XLS
There has been some confusion with Microsoft’s decision to change formats from the already established formats of Office to the new XML based ones. Excel is one of the applications that has been affected by this change with XLS being replaced by XML based XLSX. XML, which stands for Extensible Markup Language, is actually a markup language and not a file format. Because of this, it is not specific to any application and is thus used by many others including Microsoft Office’s own Word, and Powerpoint applications.
Because XLSX uses XML, it also inherits key traits of XML that are very different from XLS. XML is text based while XLS is a binary format that cannot be opened with text editors. If you try to open XLSX with a text editor, you will get garbage. That is because the XML files are archived using the ZIP format. But you can easily open it with any archiving application like WinZip and WinRar to get to the actual XML files and open them with a text editor.
XML is also an open standard compared to XLS, which is not. XLS was not problematic as long as you are using Excel. But when you open it in another application or send it to someone who is on a Mac or Linux, it is very probably that the spreadsheet will not appear as you’ve intended. With the XML based XLSX, this is not a problem. The openness of the standard ensures that just about anyone can gain information on how Microsoft encodes certain aspects into the file and adjust their application’s behavior to adapt.
XLS was a very adequate format in the old days but has been criticized due to its closed nature. Microsoft’s decision to move to XML format for their Office applications is a welcome change that makes the format a little bit more universal. Even if the format is not adapted by other applications as their default, it gives them no reason not to have the ability to correctly open Excel spreadsheets and other office application extensions.
Summary:
1.XLS is the extension for Excel spreadsheets while XML is markup language
2.XML is the basis for the replacement for XLS
3.XML is text based and while XLS is binary
4.XML is an open format while XLS is not