// =========== TYPES OF CONTENT-TYPES ===========
// APPLICATION
application/EDI-X12
application/EDIFACT
application/javascript
application/octet-stream
application/ogg
application/pdf
application/xhtml+xml
application/x-shockwave-flash
application/json
application/ld+json
application/xml
application/zip
application/x-www-form-urlencoded
// AUDIO
audio/mpeg
audio/x-ms-wma
audio/vnd.rn-realaudio
audio/x-wav
// IMAGE
image/gif
image/jpeg
image/png
image/tiff
image/vnd.microsoft.icon
image/x-icon
image/vnd.djvu
image/svg+xml
// MULTIPART
multipart/mixed
multipart/alternative
multipart/related (using by MHTML (HTML mail).)
multipart/form-data
// TEXT
text/css
text/csv
text/html
text/javascript (obsolete)
text/plain
text/xml
// VIDEO
video/mpeg
video/mp4
video/quicktime
video/x-ms-wmv
video/x-msvideo
video/x-flv
video/webm
// VND
application/vnd.oasis.opendocument.text
application/vnd.oasis.opendocument.spreadsheet
application/vnd.oasis.opendocument.presentation
application/vnd.oasis.opendocument.graphics
application/vnd.ms-excel
application/vnd.openxmlformats-officedocument.spreadsheetml.sheet
application/vnd.ms-powerpoint
application/vnd.openxmlformats-officedocument.presentationml.presentation
application/msword
application/vnd.openxmlformats-officedocument.wordprocessingml.document
application/vnd.mozilla.xul+xml

Content-Type:text/html

Content-Type: text/html; charset=UTF-8
Content-Type: multipart/form-data; boundary=something

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.