A file extension is a way of identifying what type of file a file found on your PC, tablet, or phone is. It’s a way of helping you find the type of file you’re looking for and what sort of program to open it with.

If a file is called “catphoto.jpg,” the file extension is the three letters after the dot at the very end of the file name. The extension .jpg tells me that this is an image file and that I’ll need to open with a program that can view images. It also tells Windows to put this file into the picture library.

There are a lot of file extensions out there, so trying to memorize them all can be a challenge. So, I’ve put together a basic guide for some common extensions. Today, we’ll start with common extensions pertaining to documents.


.doc – document  – this file is used by Microsoft Word prior to Office 2007 and can also be used by most word processing software like OfficeLibre and Open Office. This type of file can contain font, formatting, and other information about the document.

.docx – document –  this file is a kind of Microsoft Word file. It’s the default file starting with Word 2007. Other types of office suites like OfficeLibre and Open Office will also open a .docx file. This type of file will remember formatting as well as the content, so it will carry information like spacing, bold letters, or text color with it.

.txt – plain text – a plain text file. This type of file can be opened by almost any document editor. It supports letters, numbers, and standard punctuation, but not any type of formatting. The type of font, bold, italics or any other type of style information can’t be saved. Because of that, plain text doesn’t take up much storage space.

.rtf – rich text -this format does remember formatting such as italics, bold, underlining, and fonts.

.wpd – WordPerfect document – This is a document created by Corel’s WordPerfect program. You can open it in Word by changing the file extension to .doc.  You could also right click and use Open with to open in Word, LibreOffice, Open Office and other programs. Then save as another type of document if you want to make it easy to open in other programs.

.wks – A Microsoft Works spreadsheet file – you should be able to open this type of file in Excel and then save it as a .xlsx file.

.wps – Also a Microsoft Works file, but associated with Word processing. You should be able to open with Word and convert to another more easily shared file.

.xls – A spreadsheet file associated with Microsoft Excel. Can also be opened with spreadsheet programs like those found in Open Office or LibreOffice.

.xlsx – Also a spreadsheet file associated with later versions of Microsoft Excel. Can also be opened with spreadsheet programs like those found in Open Office or LibreOffice.

.odt – An Open Office Document. Can be opened with programs like Open Office, LibreOffice, and Microsoft Word as well as Excel and other spreadsheet programs.

.pdf – a .pdf file is designed to look exactly like a printed document and can be opened by a variety of PDF readers like Adobe Acrobat. They are designed more for viewing and not for easy editing and can be read on nearly any device.