The file extension is a suffix at the end of the file name and is used to indicate the file type. It is usually located after a point after a file name, such as .docx or .jpg, which helps computers and users identify how to process files. First, the file extension tells the operating system which program to use to open the file. For example, the .mp3 file is opened by the music player, while the .xlsx file is opened by Excel; secondly, they are also important in terms of security and can help identify malicious files such as document.pdf.exe; common extensions include .docx, .pdf of the document class, .jpg, .png of the image class, .mp3, .mp4 of the audio/video class, .js, .py of the code class, and .zip and .rar of the compressed file class; most applications have default extensions, such as Photoshop uses .psd, and AutoCAD uses .dwg; finally, the extension can be displayed in Windows through the "View" tab of the File Explorer, and in macOS, the hidden extension is viewed through the renaming operation.

A file extension is the suffix at the end of a filename that indicates what type of file it is. It usually comes after a dot — like .docx for Word documents or .jpg for image files. This little tag helps both your computer and you understand how to handle the file.

Why File Extensions Matter

File extensions tell your operating system which program should open a file. For example, .mp3 files are audio files and typically open with music players, while .xlsx files are spreadsheets made in Excel. Without the right extension, your system might not know what to do with the file — or worse, might try opening it with the wrong software.

Another reason they're important is security. Some malicious files disguise themselves by using misleading icons or names, but checking the extension can help you spot something suspicious — like a file named document.pdf.exe , which might look like a PDF but is actually an executable.

Common File Extensions You'll See

You come across file extensions every day, even if you don't always notice them. Here are some common ones grouped by category:

• Documents : .docx , .pdf , .txt , .xlsx , .pptx
• Images : .jpg , .png , .gif , .bmp , .svg
• Audio/Video : .mp3 , .wav , .mp4 , .avi , .mov
• Code/Scripts : .js , .py , .html , .css , .php
• Compressed Files : .zip , .rar , .7z

Most apps create files with their own default extensions. For instance, Photoshop uses .psd , while AutoCAD uses .dwg . Knowing these can help you identify what kind of file you're dealing with before even opening it.

How to Show File Extensions (If They're Hidden)

By default, Windows hides known file extensions. That means a file named report.docx just looks like report . If you want to see full filenames, including extensions, here's how:

• On Windows :

  • Open File Explorer.
  • Go to the "View" tab.
  • Check the box labeled "File name extensions" under "Show/hide" options.

• On macOS , extensions are usually visible. But if one is hidden:

  • Right-click the file > “Rename” > Make sure the extension is visible and editable at the end of the name.

This small change makes it easier to tell what kind of file you're looking at, especially when sorting through downloads or attachments.

It's easy to overlook file extensions because they're small and often hidden, but knowing what they mean can save time and prevent mistakes. Once you get used to paying attention, they become a helpful part of daily computing.

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