File Extensions

Learning Objectives

  • Distinguish different file types in Word and when to use them.

Let’s start by taking a look at the following scenario:

Roy is working on a report that needs to be done before noon so his coworker Riza can present the data to some prospective customers. Roy just barely manages to finish formatting the final draft. Quickly he saves the file in Microsoft Word, emails the file to Riza, and leaves to have a well-deserved lunch. When he gets back, Riza tells him she couldn’t open his file, and as a result she didn’t have the data the customers wanted and lost the sale.

Roy tries to figure out what went wrong and learns that Riza is running a different version of Microsoft Word than he is, but he’s not sure how that caused the problem.

What can cause this kind of problem? Using the wrong file extension.

A file extension is a shortened form of the file type at the end of a file name. These extensions determine your document’s file type, and the file type determines what programs can open the file. While most programs can read most file types, not every program can read every file type.

The default file type is .docx (Word Document). This file extension works in most Microsoft Word programs. However, there may be times when you want to save a different file type. For example, older versions of Microsoft Word and computers without Microsoft Word installed cannot read .docx file types. If you create a .docx file and send it to someone who has an old version of Word or no Word at all, that person probably won’t be able to read your file. If you have an old version of Word (2003 or older), you can open .docx files if you download Microsoft’s compatibility package.

Because of the variation in file type compatibility, it’s important to be mindful of what file types are readable by the programs other people have.

Practice Question


Below the field for the file name is the Save as type field, which has a dropdown menu with file extensions.

Common File Extensions in Word Processing

  • .docx (Word Document)—default Microsoft Word file, works with Microsoft Word 2007 and later. Improved scripts, macros, and other features from the older .doc.
  • .doc (Word 97–2003 Document)—default Microsoft Word file from Microsoft Word 2003 and older.
  • .txt (Plain Text)—also known as plain text format. This file type saves only the words you type—no images, no formatting, just raw text.
  • .rtf (Rich Text Format)—Like plain text, RTF saves only words, but it does save some basic formatting (like bold and italics)
  • .pdf (PDF)—PDF files are readable with Microsoft Edge (which comes with Windows 10), the free program Adobe Acrobat, and other image-viewing programs. Viewers cannot edit PDF files, but they will be able to view them regardless of their operating system or what programs they have.