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media type is a two-part identifier to file formats and format contents
transmitted on the Internet. The Internet Assigned Numbers Authority is
the official authority of the standardization and publication of these
classifications.
also almost of an old extension on the internet is MIME type.

Extension MIME Type
.doc application/msword
.dot application/msword
.docx application/vnd.openxmlformats-officedocument.wordprocessingml.document
.dotx application/vnd.openxmlformats-officedocument.wordprocessingml.template
.docm application/vnd.ms-word.document.macroEnabled.12
.dotm application/vnd.ms-word.template.macroEnabled.12
.xls application/vnd.ms-excel
.xlt application/vnd.ms-excel
.xla application/vnd.ms-excel
.xlsx application/vnd.openxmlformats-officedocument.spreadsheetml.sheet
.xltx application/vnd.openxmlformats-officedocument.spreadsheetml.template
.xlsm application/vnd.ms-excel.sheet.macroEnabled.12
.xltm application/vnd.ms-excel.template.macroEnabled.12
.xlam application/vnd.ms-excel.addin.macroEnabled.12
.xlsb application/vnd.ms-excel.sheet.binary.macroEnabled.12
.ppt application/vnd.ms-powerpoint
.pot application/vnd.ms-powerpoint
.pps application/vnd.ms-powerpoint
.ppa application/vnd.ms-powerpoint
.pptx application/vnd.openxmlformats-officedocument.presentationml.presentation
.potx application/vnd.openxmlformats-officedocument.presentationml.template
.ppsx application/vnd.openxmlformats-officedocument.presentationml.slideshow
.ppam application/vnd.ms-powerpoint.addin.macroEnabled.12
.pptm application/vnd.ms-powerpoint.presentation.macroEnabled.12
.potm application/vnd.ms-powerpoint.template.macroEnabled.12
.ppsm application/vnd.ms-powerpoint.slideshow.macroEnabled.12
.mdb application/vnd.ms-access