File Extensions
A file extension, also called a file-name extension, is the suffix at the end of a filename, which indicates what kind of file it is. For example, you can tell that the file "computer.jpg" is a JPEG image file, based on the ".jpg" file extension. Similarly, you can tell that "readme.txt" is a text document and "document.doc" is a Microsoft Word document.
Knowing what extensions common file types use can be helpful. While most file extensions consist of three characters, some have fewer (.h, .ps) while others have more (.tiff, .gadget). When you double-click a file, your computer uses the file's extension to determine what program should open it. It is possible to change file's extension, which may also change the program your computer uses to open the file.
Therefore, you should be careful when changing a file's extension since your computer may be unable to open the file. For example, if you change a file with a .txt extension to a .doc extension, Microsoft Word should open it. However, if you change a .txt file to a .jpg file, the file will not open.
Since there are tens of thousands of software programs available, there are also tens of thousands of file-name extensions. While it is helpful to learn the most commonly used file extensions, it is not possible to remember them all. So I've compiled a list below of common file extensions and their uses:
Text Extensions
-------------------------------------------
.doc Word Document
.docx Word Open XML Document
.log Log File
.msg Outlook Mail Message
.pages Pages Document
.rtf Rich Text Format File
.txt Plain Text File
.wpd WordPerfect Document
.wps Microsoft Works Word Processor Document
Image Extensions
------------------------------------------
.bmp Bitmap Image File
.gif Graphical Interchange Format File
.jpg JPEG Image File
.png Portable Network Graphic
.psd Photoshop Document
.psp Paint Shop Pro Image File
.thm Thumbnail Image File
.tif Tagged Image File
Video Extensions
-------------------------------------------
.3g2 3GPP2 Multimedia File
.3gp 3GPP Multimedia File
.avi Audio Video Interleave File
.flv Flash Video File
.mov Apple QuickTime Movie
.mp4 MPEG-4 Video File
.mpg MPEG Video File
.rm Real Media File
.swf Flash Movie
.wmv Windows Media Video File
Audio Extensions
-------------------------------------------
.aac Advanced Audio Coding File
.aif Audio Interchange File Format
.mp3 MP3 Audio File
.mpa MPEG-2 Audio File
.ra Real Audio File
.wav WAVE Audio File
.wma Windows Media Audio File
Web Extensions
-------------------------------------------
.asp Active Server Page
.cer Internet Security Certificate
.csr Certificate Signing Request File
.css Cascading Style Sheet
.htm Hypertext Markup Language File
.html Hypertext Markup Language File
.js JavaScript File
.jsp Java Server Page
.php Hypertext Preprocessor File
.xhtml Extensible Hypertext Markup Language File
Knowing what extensions common file types use can be helpful. While most file extensions consist of three characters, some have fewer (.h, .ps) while others have more (.tiff, .gadget). When you double-click a file, your computer uses the file's extension to determine what program should open it. It is possible to change file's extension, which may also change the program your computer uses to open the file.
Therefore, you should be careful when changing a file's extension since your computer may be unable to open the file. For example, if you change a file with a .txt extension to a .doc extension, Microsoft Word should open it. However, if you change a .txt file to a .jpg file, the file will not open.
Since there are tens of thousands of software programs available, there are also tens of thousands of file-name extensions. While it is helpful to learn the most commonly used file extensions, it is not possible to remember them all. So I've compiled a list below of common file extensions and their uses:
Text Extensions
-------------------------------------------
.doc Word Document
.docx Word Open XML Document
.log Log File
.msg Outlook Mail Message
.pages Pages Document
.rtf Rich Text Format File
.txt Plain Text File
.wpd WordPerfect Document
.wps Microsoft Works Word Processor Document
Image Extensions
------------------------------------------
.bmp Bitmap Image File
.gif Graphical Interchange Format File
.jpg JPEG Image File
.png Portable Network Graphic
.psd Photoshop Document
.psp Paint Shop Pro Image File
.thm Thumbnail Image File
.tif Tagged Image File
Video Extensions
-------------------------------------------
.3g2 3GPP2 Multimedia File
.3gp 3GPP Multimedia File
.avi Audio Video Interleave File
.flv Flash Video File
.mov Apple QuickTime Movie
.mp4 MPEG-4 Video File
.mpg MPEG Video File
.rm Real Media File
.swf Flash Movie
.wmv Windows Media Video File
Audio Extensions
-------------------------------------------
.aac Advanced Audio Coding File
.aif Audio Interchange File Format
.mp3 MP3 Audio File
.mpa MPEG-2 Audio File
.ra Real Audio File
.wav WAVE Audio File
.wma Windows Media Audio File
Web Extensions
-------------------------------------------
.asp Active Server Page
.cer Internet Security Certificate
.csr Certificate Signing Request File
.css Cascading Style Sheet
.htm Hypertext Markup Language File
.html Hypertext Markup Language File
.js JavaScript File
.jsp Java Server Page
.php Hypertext Preprocessor File
.xhtml Extensible Hypertext Markup Language File