What is a File Extension? A Technical Guide In Simple Words

Do you know what a file extension is? If not, don’t feel bad. Most people don’t. Even many tech guys (aka the people who should know this stuff) are fuzzy on the details. That’s why I have prepared this article for you. A file extension is simply a few letters located at the end of the filename after the last dot from the end.

For example, a PDF document would have the .pdf file extension. Knowing what type of file you’re dealing with is important because different types of files can be opened and read in different ways. So now that you know what a file extension is, next time someone asks you about one, you’ll be able to sound like a smartypants!

If you are looking to try some sample files, you can download the test files that we added to our home page. You can also use our test files to test your internet speed.

Types of File Extension

There are hundreds of file extensions. However, there are only about 20 different types of files. Let’s see one by one.

1. Audio Files

Audio files come in many different formats, each with its own unique extension. Some of the more common audio file extensions include MP3, WAV, and AAC.

MP3 is a popular compression format that offers good quality audio at smaller file sizes. We often use it for music files, as well as voice recordings.

WAV is a standard audio format that stores uncompressed audio data. This makes it a bit larger than MP3 files, but it offers the best quality of any compressed audio format.

AAC is another compression format that offers good quality audio at a smaller file size. It is often used for music files, as well as voice recordings. AAC is also supported by most mobile devices, making it a popular choice for those looking to listen to their audio files on the go.

Knowing the different audio file extensions can help you choose the best format for your needs. If you need high-quality audio, WAV files are a good choice. If you’re looking for a smaller file size, AAC or MP3 files are a better option.

2. Video Files

There are a variety of video file extensions that can be used on different devices. The most common video file extensions are .avi, .mpeg, and .mov, and .mp4, etc. However, many other types of video file extensions can be used depending on the device or program being used. For example, .wmv is a common video file extension used for videos that are streamed online.

Some devices, such as the iPhone, use specific video file extensions that are not common on other devices. For example, the iPhone uses the .m4v file extension.

This is a MPEG-4 video file that has been compressed using the H.264 codec. The iPhone can also play other common types of video file extensions such as .avi and .mov.

There are also digital video file formats that do not have a specific file extension associated with them. These digital files can typically be played by several different programs such as Windows Media Player, Quicktime, and RealPlayer.

3. Image Files

An image file is a digital file that contains a graphic representation of a picture or photograph. Image files are typically saved in either JPEG or GIF format.

The JPEG (Joint Photographic Experts Group) format is a compressed image file that is commonly used to store digital photos. The JPEG format uses lossy compression, which means that some of the data from each image are lost during compression.

This can result in a smaller file size, but images that have been compressed this way tend to look slightly blurred or pixelated.

4. Text Documents

A text document is a digital file that contains text data. Text documents are typically saved in ASCII or Unicode format.

The ASCII (American Standard Code for Information Interchange) format is a character encoding scheme that uses 7 bits to represent each character. This results in 128 possible characters, which is enough to represent most English texts. The ASCII format is typically used to save simple text documents.

The Unicode (Universal Character Set) format is a character encoding scheme that uses 16 bits to represent each character. This results in a total of 65,536 possible characters, which is enough to represent most texts in multiple languages. The Unicode format is typically used to save complex text documents that contain characters from multiple languages.

5. Archive Files (ZIP, RAR, etc.)

An archive file is a digital file that contains one or more other files, but they are saved in compressed format. Several different types of compression formats can be used to compress the contents of an archive file.

For example, ZIP files can use either lossless or lossy compression on the data that is stored in the ZIP file. This means that the size of the ZIP file can be reduced, but the quality of the data within the ZIP file will not be affected. RAR files use a lossless compression format, which means that no data is lost during compression. This results in a smaller file size, but the images and other files within the RAR file will not be blurred or pixeled.

RAR is commonly used to distribute files that are too large to email or transfer via FTP.

6. Portable Document Format Files (.pdf)

7. Excel Spreadsheets

8. Word Documents

9. PowerPoint Presentations

10. HTML Web Pages

HTML web pages use different linked files including javascript (.js), cascading style sheet (.css), hyper text markup language (.html) and other web font files (.woff, .woff2, .svg, .eot, etc.).

11. CSV Data Sets (.csv, .tsv, .txt, etc.)

12. Images Files

Image files use different extensions like .bmp, .jpg, .gif, .jpeg, .png, .tif, .tiff, etc.

13. Windows Icon Images (.ico)

14. Scalable Vector Graphics Images (.svg)

15. PostScript Files (.ps)

16. Adobe Photoshop Documents (.psd)

17. Rich Text Format Files (.rtf)

18. AutoCAD Drawings (.dwg, .dxf)

19. 3D Studio Max Scene Files (.max)

20. Microsoft Visio Diagrams (.vsd, .vdx)

21. SQL Data Files (.sql)

22. XML Files (.xml)

23. SWF Flash Movies (.swf)

24. FLA ActionScript Files (.fla)

25. WebGL 3D Scene Files (.gltf, .glb, .glTF)

26. Data Matrix Bar Code Images (.dat)

27. QR Code Bar Code Images (.qrcode)

28. Microsoft OneNote Notebooks (.one)

29. Adobe InDesign Documents (.indd)

30. Apple iWork Pages Documents (.pages, .key)

31. Audio CD Tracks (.cda)

32. Windows Media Audio and Video Files (.wma, .asf, .wmv, etc.)

33. MPEG Video Files (.mpg, .mpeg, .mp4, etc.)

34. MPEG Audio Files (.m4a, .m4b, .m4p)

MPEG Audio files are files with the AAC encoding format developed by MPEG, a standard for digital media compression. AAC is used in many audio file formats. The most common use of MPEG Audio Files Extension is for music files, but they can also be used for other types of audio files.

35. TIFF Image Files (.tif, .tiff)

The TIFF file extension is short for the tagged image file format. It’s a common graphic file format used for images that contain high-resolution graphics, such as scanned documents and digital photos. TIFF files can be saved in a variety of color depths and compression schemes, making them ideal for storing graphics that have a wide range of color and detail.

We can also create TIFF files with several different image editors, including GIMP and Photoshop. They can also be opened by a variety of different programs, including web browsers and word processors.

Can I change the file extension?

Yes, you can change the file extension. The process for doing so may vary depending on the operating system you are using, but in general, it is a fairly simple process.

Changing File Extension On Windows

To change the file extension on a Windows PC, right-click on the file and select Rename. In the text box that pops up, type in the new extension and hit Enter.

Changing File Extension on MAC

To change the file extension on a Mac, highlight the file in Finder and press Command+I. In the Info window that pops up, click on the Name & Extension tab. Change the extension in the text box and click Apply.

Keep in mind that you may not be able to open a file with a different extension. This is because some programs open certain file types and extensions by default (i.e., Word by default opens .docx files).

To avoid this, you can right-click on the file and select Open With or Always Open With, then choose the program that should always open that specific type of file.

What Happens if I change the file extension?

Changing the file extension on a document can be helpful in certain circumstances, such as making a document easier to share or saving space on your computer.

However, it’s important to know what happens when you change a file extension, since some changes may not be reversible.

When you change a file extension, you’re telling the computer to treat the file as a different type of document. In most cases, the computer will still be able to open your original document even if you change its extension.

However, in some cases changing a file extension can make the document impossible to open. This is because the computer may not have a program installed that can open the new type of document.

For example, if you change a Microsoft Word document’s extension from .docx to .pdf, the computer won’t know what program to use to open it.

In some cases, you may be able to change the file extension back to the original type and regain access to the document.

However, in other cases, you may not be able to reverse the change without losing information from the document. It’s important to be aware of these risks before changing a file extension.

If you need any help changing a file’s extension, Windows includes a guide on how to do so here.

Remember to be aware of the risks involved before changing a file extension, and to back up any important documents beforehand.


A file extension is simply a few words at the end of the file name after the last dot. File extension tells what type of this file is and then the operating system knows the program to open when you open a certain file.

There are various file extensions but the most commonly used file extensions are .jpg, .png, .exe, .gif, .docx, .pdf, and .txt, etc.

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1. What is a file extension?

File extensions are the letters at the end of a filename (the part after the last dot – usually called ‘the extension’). They tell you what type of file it is.

2. What are the most common file extensions?

The most common file extensions are:

  • .txt – text file
  • .jpg – image file
  • .docx – Microsoft Word document
  • .mp3 – audio file
  • .mp4 – video file

3. What does a file extension look like?

An example of a file extension is .txt or .docx, for example: that it’s a text file or Microsoft Word document.

4. What does the file extension .exe do?

A program called an ‘executable’ is a file that runs when you click on it. The .exe means that the file contains an executable program (programs like Task Manager, Calculator, and MS Paint are located in the Windows folder – they are .exe files).

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