Understanding File Extensions

Jim Cerny, Sarasota Technology Users Group

So someone sends you a file attached to their email – you try to open the file and you can’t, why is that?  I mean they obviously could open the file on their computer, why couldn’t you open it on yours?  Unfortunately, this is the frustrating part about FILE EXTENSIONS (also known as “file types”).

If you use a program to CREATE a file, it is nice to have the SAME PROGRAM to open or work with the file you created. Naturally, if you use your computer to create a file then your computer has the program needed to open the file later. The problem is when someone creates a file on their computer and sends it to you – you need to have a program that can open the file on your computer. Let’s look at one example:

I have the Microsoft Word app (or program) on my computer and I create a new document with it. I save the document as a file, and the computer assigns it a “file extension” or “file type” of “.docx”. The file extension is always the last three or four characters of the file name right after the dot. This indicates that this file was created using the latest version of Word. If I send this file (as an attachment to an email) to someone else and they do NOT have Word, they cannot open the file!

It is an option in Windows whether to display the file extension, so your computer may not show you the file extension as part of the file name. To see the file extension when you use File Explorer, open the File Explorer app, click on the “View” menu tab and check the box labelled “File Name Extensions”. This will display the file extensions (file type) as part of the file name for all files.

Things have changed over the past few years as there are more options to open the file to READ it or to EDIT it. Your computer may suggest some internet sites or free apps that may be able to open the file for you.

A good app like Microsoft Word may allow you to save your file as a different type of file – so you can pick one that is easier for more people to open. You could save it as a “.pdf” or “.rtf” file type if you want. A “.pdf” file can be opened by many apps but usually, the contents, or text, of the file can NOT be edited, only read. The “.rtf” file type (Rich Text File) can also be opened by several other apps and can be edited, BUT the text will have lost any formatting or options used in Microsoft Word.

Are you working with photo files?  Most photos or pictures today are saved as a “.jpg” file type and any app that can open or work with photos will be able to open this file. That’s nice.

Here are just a few of the most popular file extensions (types):

.doc or .docx – Microsoft Word

.html – webpage

.jpg – picture or photo image

.pdf – a document file that can be open or read by many apps but cannot be edited

.rtf – rich text file that contains formatting (the Wordpad app creates these files)

.txt – plain text file will no formatting

.xls and .xlsx – Microsoft Excel spreadsheet

There are probably many thousands of different file types, but thankfully you do not have to know them all. If you have any questions about a particular file type, just Ask Google and you will find out what apps could have created the file and which apps can open or work with that file.

I know this all sounds a bit confusing, but you should only run into a problem when you try to open a file that you did not create on your computer. Should this happen you may have to contact the person who sent you the file and ask them to send it to you again as a different file type – one that you know you can open.

Hopefully, you will become comfortable with the most common file types that you use. Remember you can always Ask Google for help!

Republished from Sarasota Monitor, the journal of Sarasota Technology Users Group