accept

If the value of the type attribute is file, this attribute indicates the types of files that the server accepts; otherwise it is ignored. The value must be a comma-separated list of unique content type specifiers:
  A file extension starting with the STOP character (U+002E). (E.g.: ".jpg,.png,.doc")
  A valid MIME type with no extensions
  audio/* representing sound files HTML5
  video/* representing video files HTML5
  image/* representing image files HTML5
