When the client navigator requests a file to the webserver, in the response the webserver sends the type of file. This is called the mime-type.
Most of the time the mime types are based on the extension of the file name.
This are the most common extensions and their mime types:
MIME TYPE EXTENSION application/msword doc application/octet-stream bin dms lha lzh exe class so dll application/pdf pdf application/vnd.ms-excel xls application/vnd.ms-powerpoint ppt application/x-javascript js application/x-shockwave-flash swf application/zip zip audio/midi mid midi kar audio/mpeg mpga mp2 mp3 audio/x-pn-realaudio ram rm audio/x-realaudio ra audio/x-wav wav image/bmp bmp image/gif gif image/ief ief image/jpeg jpeg jpg jpe image/png png image/tiff tiff tif text/css css text/html html htm text/plain asc txt text/xml xml xsl video/mpeg mpeg mpg mpe video/quicktime qt mov video/x-msvideo avi
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