Your computer has many different types of files on it, and each one has its own file extension. A file extension is a three- or four-letter identifier found at the end of a file name and following a period. These extensions tell you about the characteristics of a file and its use. In this lesson, we'll go over some examples of these extensions, as well as how to determine a particular file's extension.
A file type is a name given to a specific kind of file. For example, a Microsoft Word document (.doc, .docx, etc.) and an Adobe document (.pdf) are two different file types. While these file types are associated with individual applications, other file types, such as rich text (RTF) files and audio (MP4) files are standard file types that can be opened by multiple programs. File extensions also tell your computer which applications to use when opening that file.
Examples of file extensions
- A JPEG uses the .jpg or .jpeg extension (for example, image.jpg).
- A Word document uses the .docx extension, or .doc for older versions (for example, CoverLetter.docx).
- An audio file may have a .wav or .mp4 extension (for example, rhyme_rap.mp4).
- An Excel spreadsheet uses the .xlsx extension, or .xls for older versions (for example, budget.xls). An Excel file that is saved as a "Comma Separated Value" file will have a .csv extension.
- There are some file extensions can only be accessed on an Apple/Mac devices. Please note, not all instructors have access to these types of devices. Please be sure to follow the instructions below to save your files as a .pdf, if permitted for your assignment if your files are any of these: .pages, .numbers, .key, and .heic (iPhone photos)
Want to preserve your formatting? If your assignment allows, you can preserve your formatting (and disable editing) by saving your files as a .pdf file. PDF stands for "Portable Document Format", meaning your formatting (like fonts used) will be able to be viewed by others, no matter what type of device they have. Please first verify that a PDF file is acceptable for your assignment, then review these steps to Save As or Create a PDF.
Using Mac/Apple (only) applications? Saving files as PDFs is also very helpful in cases when proprietary applications are used to create files, like using Pages on a Mac. Only other Mac users will be able to access a Pages (or .pages) file. Please first verify that a PDF file is acceptable for your assignment, then review these steps to Save As or Create a PDF.
Hidden file extensions
Some operating systems hide file extensions by default to reduce clutter. It is possible to show the file extensions if they're hidden. Click the links below to see how to show file extensions in Windows and macOS:
You can also usually tell what the file type is by looking at the file's icon. For example, the Word document looks like a file with a W in the corner, while an Excel spreadsheet looks like a file with an X in the corner.
