Editing Filename extension (section)

=== Compared to MIME type ===
In many [[Internet protocol suite|Internet]] protocols, such as [[HTTP protocol|HTTP]] and [[MIME|MIME email]], the type of a bitstream is stated as the [[media type]], or MIME type, of the stream, rather than a filename extension. This is given in a line of text preceding the stream, such as ''Content-type: text/plain''.

There is no standard mapping between filename extensions and media types, resulting in possible mismatches in interpretation between authors, web servers, and client software when transferring files over the Internet. For instance, a content author may specify the extension ''svgz'' for a compressed [[Scalable Vector Graphics]] file, but a web server that does not recognize this extension may not send the proper content type ''application/svg+xml'' and its required compression header, leaving web browsers unable to correctly interpret and display the image.

[[BeOS]], whose [[Be File System|BFS]] file system supports extended attributes, would tag a file with its media type as an extended attribute. Some [[desktop environments]], such as [[KDE Plasma]] and [[GNOME]], associate a media type with a file by examining both the filename suffix and the contents of the file, in the fashion of the [[file (command)|file]] command, as a [[heuristic]]. They choose the application to launch when a file is opened based on that media type, reducing the dependency on filename extensions. [[macOS]] uses both filename extensions and media types, as well as [[OSType|file type codes]], to select a [[Uniform Type Identifier]] by which to identify the file type internally.