File Extensions

File extension is a postfix in a file name that often defines the file type and, sometimes, a particular file format. In a file name, a dot precedes this postfix to separate an extension from a file name.

Types of File Extensions

Here are only the examples of file extension types, to show how to find and read this information.

• In a filename "common.txt", the "txt" is an extension showing that this is a plain text file. Note that the extension has no data about character encoding used in this "plain" file! This file opened in another OS can be unreadable!
• Different applications can save a formatted text under some different extensions; e.g., for Microsoft Word a text file may have a name "text.docx", and for LibreOffice Writer, the same file may have a name "text.odt". Here, "docx" and "odf" are extensions for different formats.

Using File Extensions

With file extensions, you can quickly select all files of a single type to make some actions over these files. To do it, use your file selection filters in your browsing software (e.g., in Windows Explorer) and enter in a file filter the next string: "*.[type]" (where the "[type]" is a substitution to an extension).

Examples of File Extension Filter Strings

• "*.txt" for all text files;
• ".doc*" for all Microsoft Word documents, both older and newer versions;
• "*.jp*g" for all graphic files in a JPEG compressed photo format.