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

GED file extension

GEDCOM Genealogy Data File

Data Files

H file extension

C/C++/Objective-C Header File

Developer Files

IBOOKS file extension

Multi-Touch iBook

Data Files

M4A file extension

MPEG-4 Audio File

Audio Files

MAX file extension

3ds Max Scene File

3D Image Files

PCT file extension

Picture File

Layout Files

PDB file extension

Program Database

Database Files

RM file extension

Real Media File

Video Files

SH file extension

Bash Shell Script

Developer Files

SRT file extension

SubRip Subtitle File

Video Files

THM file extension

Thumbnail Image File

Raster Image Files

XLS file extension

Excel Spreadsheet

Spreadsheet Files

XLSX file extension

Microsoft Excel Open XML Spreadsheet

Spreadsheet Files

YUV file extension

YUV Encoded Image File

Raster Image Files

ZIP file extension

Zipped File

Compressed Files