MIME (Multipurpose Internet Mail Extensions) 是描述消息内容类型的标准，用来表示文档、文件或字节流的性质和格式。MIME 消息能包含文本、图像、音频、视频以及其他应用程序专用的数据。

浏览器通常使用 MIME 类型（而不是文件扩展名）来确定如何处理URL，因此 Web服务器在响应头中添加正确的 MIME 类型非常重要。如果配置不正确，浏览器可能会无法解析文件内容，网站将无法正常工作，并且下载的文件也会被错误处理，如下图，无法下载HTTP文件服务器上的apk文件。

解决方法

默认情况下，IIS是不允许没有注册到 IIS 的 MIME文件下载，IIS 默认支持哪些 MiME类型呢，我们可以在 IIS 站点的属性中看得到。只可惜一些常用的文件类型都是默认不支持的，如：.apk .iso .7z bt种子等，但我们可以手动添加 MIME 类型让 IIS 可以支持我们指定的文件下载。方法如下：

1、打开 IIS 管理器，选中服务器，然后在右边窗口找到 [MIME类型] 图标，双击打开；

2、在打开的 [MIME类型] 设置窗口中，点击右边的 [添加] 按钮，建立新的MIME类型，如下图，扩展名中填写 ".apk"，MIME类型中填写apk的MIME类型 "application/vnd.android.package-archive"，单击“确定”保存设置。

3、打开命令行，输入 iisreset 命令重启 IIS 管理器，或者返回IIS服务器管理，点击最右边的“管理网站”下面的 [重新启动] 按钮。

4、现在，再次打开服务器上的apk文件，即可正常下载了，如下图。

知识拓展

1、MIME 类型通用结构：type/subtype

MIME 的组成结构非常简单，由类型与子类型两个字符串中间用 / 分隔而组成，不允许有空格。type 表示可以被分多个子类的独立类别，subtype 表示细分后的每个类型。

MIME 类型对大小写不敏感，但是传统写法都是小写。

两种主要的 MIME 类型在默认类型中扮演了重要的角色：

●text/plain 表示文本文件的默认值。
●application/octet-stream 表示所有其他情况的默认值。

2、常见的 MIME 类型

扩展名	MIME 类型
.323	text/h323
.7z	application/octet-stream
.acx	application/internet-property-stream
.ai	application/postscript
.aif	audio/x-aiff
.aifc	audio/x-aiff
.aiff	audio/x-aiff
.apk	application/vnd.android.package-archive
.asf	video/x-ms-asf
.asr	video/x-ms-asf
.asx	video/x-ms-asf
.au	audio/basic
.avi	video/x-msvideo
.axs	application/olescript
.bas	text/plain
.bcpio	application/x-bcpio
.bin	application/octet-stream
.bmp	image/bmp
.c	text/plain
.cat	application/vnd.ms-pkiseccat
.cdf	application/x-cdf
.cer	application/x-x509-ca-cert
.class	application/octet-stream
.clp	application/x-msclip
.cmx	image/x-cmx
.cod	image/cis-cod
.cpio	application/x-cpio
.crd	application/x-mscardfile
.crl	application/pkix-crl
.crt	application/x-x509-ca-cert
.csh	application/x-csh
.css	text/css
.dcr	application/x-director
.der	application/x-x509-ca-cert
.dir	application/x-director
.dll	application/x-msdownload
.dmg	application/octet-stream
.dms	application/octet-stream
.doc	application/msword
.dot	application/msword
.dvi	application/x-dvi
.dxr	application/x-director
.eps	application/postscript
.etx	text/x-setext
.evy	application/envoy
.exe	application/octet-stream
.fif	application/fractals
.flr	x-world/x-vrml
.gif	image/gif
.gtar	application/x-gtar
.gz	application/x-gzip
.h	text/plain
.hdf	application/x-hdf
.hlp	application/winhlp
.hqx	application/mac-binhex40
.hta	application/hta
.htc	text/x-component
.htm	text/html
.html	text/html
.htt	text/webviewhtml
.ico	image/x-icon
.ief	image/ief
.iii	application/x-iphone
.ins	application/x-internet-signup
.isp	application/x-internet-signup
.iso	application/octet-stream
.ipa	application/octet-stream.ipa
.jfif	image/pipeg
.jpe	image/jpeg
.jpeg	image/jpeg
.jpg	image/jpeg
.js	application/x-javascript
.latex	application/x-latex
.lha	application/octet-stream
.lsf	video/x-la-asf
.lsx	video/x-la-asf
.lzh	application/octet-stream
.m13	application/x-msmediaview
.m14	application/x-msmediaview
.m3u	audio/x-mpegurl
.man	application/x-troff-man
.mdb	application/x-msaccess
.me	application/x-troff-me
.mht	message/rfc822
.mhtml	message/rfc822
.mid	audio/mid
.mny	application/x-msmoney
.mov	video/quicktime
.movie	video/x-sgi-movie
.mp2	video/mpeg
.mp3	audio/mpeg
.mpa	video/mpeg
.mpe	video/mpeg
.mpeg	video/mpeg
.mpg	video/mpeg
.mpp	application/vnd.ms-project
.mpv2	video/mpeg
.ms	application/x-troff-ms
.mvb	application/x-msmediaview
.nws	message/rfc822
.oda	application/oda
.p10	application/pkcs10
.p12	application/x-pkcs12
.p7b	application/x-pkcs7-certificates
.p7c	application/x-pkcs7-mime
.p7m	application/x-pkcs7-mime
.p7r	application/x-pkcs7-certreqresp
.p7s	application/x-pkcs7-signature
.pbm	image/x-portable-bitmap
.pdf	application/pdf
.pfx	application/x-pkcs12
.pgm	image/x-portable-graymap
.pko	application/ynd.ms-pkipko
.pma	application/x-perfmon
.pmc	application/x-perfmon
.pml	application/x-perfmon
.pmr	application/x-perfmon
.pmw	application/x-perfmon
.pnm	image/x-portable-anymap
.pot,	application/vnd.ms-powerpoint
.ppm	image/x-portable-pixmap
.pps	application/vnd.ms-powerpoint
.ppt	application/vnd.ms-powerpoint
.prf	application/pics-rules
.ps	application/postscript
.pub	application/x-mspublisher
.qt	video/quicktime
.ra	audio/x-pn-realaudio
.ram	audio/x-pn-realaudio
.ras	image/x-cmu-raster
.rgb	image/x-rgb
.rmi	audio/mid
.roff	application/x-troff
.rtf	application/rtf
.rtx	text/richtext
.scd	application/x-msschedule
.sct	text/scriptlet
.setpay	application/set-payment-initiation
.setreg	application/set-registration-initiation
.sh	application/x-sh
.shar	application/x-shar
.sit	application/x-stuffit
.snd	audio/basic
.spc	application/x-pkcs7-certificates
.spl	application/futuresplash
.src	application/x-wais-source
.sst	application/vnd.ms-pkicertstore
.stl	application/vnd.ms-pkistl
.stm	text/html
.svg	image/svg+xml
.sv4cpio	application/x-sv4cpio
.sv4crc	application/x-sv4crc
.swf	application/x-shockwave-flash
.t	application/x-troff
.tar	application/x-tar
.tcl	application/x-tcl
.tex	application/x-tex
.texi	application/x-texinfo
.texinfo	application/x-texinfo
.tgz	application/x-compressed
.tif	image/tiff
.tiff	image/tiff
.tr	application/x-troff
.trm	application/x-msterminal
.tsv	text/tab-separated-values
.txt	text/plain
.uls	text/iuls
.ustar	application/x-ustar
.vcf	text/x-vcard
.vrml	x-world/x-vrml
.wav	audio/x-wav
.wcm	application/vnd.ms-works
.wdb	application/vnd.ms-works
.wks	application/vnd.ms-works
.wmf	application/x-msmetafile
.wps	application/vnd.ms-works
.wri	application/x-mswrite
.wrl	x-world/x-vrml
.wrz	x-world/x-vrml
.xaf	x-world/x-vrml
.xbm	image/x-xbitmap
.xla	application/vnd.ms-excel
.xlc	application/vnd.ms-excel
.xlm	application/vnd.ms-excel
.xls	application/vnd.ms-excel
.xlt	application/vnd.ms-excel
.xlw	application/vnd.ms-excel
.xof	x-world/x-vrml
.xpm	image/x-xpixmap
.xwd	image/x-xwindowdump
.z	application/x-compress
.zip	application/zip