Have you ever received an email with an attachment and, from the file extension, had no idea what type of file it was? Yep, I have too. Today, that ends. Prepare yourself for a list of the most common file type extensions. Although this list isn't complete, I think I've hit all the high notes.

Bookmark it so you can reference it the next time a mysterious attachment appears in your inbox.

Text Files

.doc - Microsoft Word Document
.docx - Microsoft Word Open XML Document
.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 Files

.bmp - Bitmap Image File
.gif - Graphical Interchange Format File
.jpg - JPEG Image
.png - Portable Network Graphic
.psd - Adobe Photoshop Document
.thm - Thumbnail Image File
.tif - Tag Image File Format

Video Files

.asf - Advanced Systems Format File
.asx - Microsoft ASF Redirector File
.avi - Audio Video Interleave File
.flv - Flash Video File
.m4v - MPEG-4 Video File
.mov - Apple QuickTime Movie
.mp4 - MPEG-4 Video File
.mpg - MPEG Video File
.swf - Shockwave Flash Movie
.vob - DVD Video Object File
.wmv - Windows Media Video File

Audio Files

.aif - Audio Interchange File Format
.iff - Interchange File Format
.m3u - Media Playlist File
.m4a - MPEG-4 Audio File
.mp3 - MP3 Audio File
.mpa - MPEG-2 Audio File
.ra - Real Audio File
.wav - WAVE Audio File
.wma - Windows Media Audio File

Data Files

.csv - Comma Separated Values File
.dat - Data File
.pps - PowerPoint Slide Show
.ppt - PowerPoint Presentation
.pptx - PowerPoint Open XML Presentation
.sdf - Standard Data File
.vcf - vCard File
.xml - XML File
.htm - Hypertext Markup Language File
.html - Hypertext Markup Language File

Spreadsheet Files

.xlr - Works Spreadsheet
.xls - Excel Spreadsheet
.xlsx - Microsoft Excel Open XML Spreadsheet

Compressed Files

.rar - WinRAR Compressed Archive
.tar - Consolidated Unix File Archive
.zip - Zipped File