What is a File Extension (file format)?

In computing, a file extension is a suffix added to the name of a file to indicate the file’s format and how its data is organized. This helps software programs know how to access and use the file correctly. File extensions also give users a quick idea of the types of files they are dealing with.

A file extension comes after the period in a filename and usually has three or four characters. For example, in the file name “testfile1.txt,” the extension is “.txt,” which shows it is a plain text document. In “testfile2.jpeg,” the “.jpeg” extension indicates it is an image file in the JPEG format.

File extensions can be short, like one or two characters, or longer, such as “.catproduct”. The operating system (OS) needs to recognize the file extension to open it with the correct program. If the OS does not know which program to use, the user must choose the right one.

These extensions allow you to see the type of the file at a glance without looking into the folder and without notice, be it the text document, an image, or something else.

• In the name of the file “testfile1.txt”, “.txt” is a file extension that indicates the file type of the text as a text file.
• The ending “.jpeg” of “testfile2.jpeg” suggests that it is an image. 
• A file name with many dots may not mean a lot, for instance, “testfile.3.2.csv”. But the part that matters here is the “.csv” at the end of the file name. It indicates that the associated file is a spreadsheet.

Occasionally, you might come across a tricky file called “testfile4.xlsx.exe,” which could be a trickster innovation of some other person who would loathe trying to get a hazardous program onto your computer only by pretending that it is a spreadsheet.

Also Check –

• How to Change File Extension in Windows?
• How to Change File Extension in Mac?

A file extension is a suffix at the end of a file name that indicates the file’s format or type, usually consisting of three or four letters following a period. For example, in “document.txt,” the “.txt” part is the file extension.

File extensions help operating systems and software determine how to open and handle the file. Common extensions include “.txt” for plain text files, “.doc” or “.docx” for Microsoft Word documents, “.xls” or “.xlsx” for Excel spreadsheets, “.jpg” or “.jpeg” for JPEG images, “.png” for PNG images, “.pdf” for PDF files, “.mp3” for MP3 audio files, and “.mp4” for MP4 video files. Recognizing these extensions ensures that files are accessed and edited with the correct applications, aiding in efficient file management.