File extensions – definition and basic information


File extensions are the integral parts of the files that are on each computer. Often, when working on a computer, we encounter a wide range of files, such as docx, ppt, part, mp3 or rmvb. We realize that they are there – but we often do not know what they are for on our computer.

File extension, also known as the filename extension is a suffix added to the name of a computer file, usually consisting of a number of characters placed after the last dot in the filename, which gives us information about its coding. In other words a file extension is a file format. It allows the operating system (e.g. Windows) to recognize what program it should try to open the file.

In the table below you will find a random selection of popular file extensions.


File extension The full name of the file Category

ASP file extension

Active Server Page

Web Files

ASX file extension

Microsoft ASF Redirector File

Video Files

BMP file extension

Bitmap Image File

Raster Image Files

CER file extension

Internet Security Certificate

Web Files

CGI file extension

Common Gateway Interface Script

Executable Files

CSR file extension

Certificate Signing Request File

Web Files

LNK file extension

Windows File Shortcut

System Files

OTF file extension

OpenType Font

Font Files

PSD file extension

Adobe Photoshop Document

Raster Image Files

PY file extension

Python Script

Developer Files

ROM file extension

N64 Game ROM File

Game Files

SRT file extension

SubRip Subtitle File

Video Files

XLR file extension

Works Spreadsheet

Spreadsheet Files

XML file extension

XML File

Data Files

3G2 file extension

3GPP2 Multimedia File

Video Files