Protect your training budget AND save money with our new pre-payment vouchers.
Revealing how Excel workbooks are actually stored as zipped XML files
Did you know that Excel workbooks are really just a collection of XML files, all zipped together? We didn’t either, so we thought we'd tell the world.

Posted by Andy Brown on 16 May 2014

You need a minimum screen resolution of about 700 pixels width to see our blogs. This is because they contain diagrams and tables which would not be viewable easily on a mobile phone or small laptop. Please use a larger tablet, notebook or desktop computer, or change your screen resolution settings.

The true nature of Excel workbooks - zipped files

Trivia question: what format do Excel workbooks use?  If your answer is a proprietary Microsoft format, you couldn't be further from the truth.

Let's create a simple Excel workbook and dissect it:

Owly workbook

A simple workbook containing 3 sheets

Here's what this looks like in Windows Explorer:

Workbook in Explorer

The workbook above.


So far, so what.  But let's now change the file extension from .xlsx to .zip (ignoring any complaints from Microsoft):

The zipped workbook

You can now see that the workbook is actually a collection of zipped files.

When you double-click on the file now, you can see its true contents:

The workbook contents

The true contents of the workbook: the worksheets folder contains one XML file for each worksheet.

Here's a sample of the first worksheet:

A worksheet as XML

The XML underlying each worksheet is completely transparent.

As Michael Caine apparently didn't say: "Not a lot of people know that!".

This blog has 0 threads Add post