最早的HTTP協議中,並沒有附加的數據類型信息,所有傳送的數據都被客戶程序解釋爲超文本標記語言HTML 文檔,而爲了支持多媒體數據類型,HTTP協議中就使用了附加在文檔之前的MIME數據類型信息來標識數據類型。
MIME意爲多目Internet郵件擴展,它設計的最初目的是爲了在發送電子郵件時附加多媒體數據,讓郵件客戶程序能根據其類型進行處理。然而當它被HTTP協議支持之後,它的意義就更爲顯著了。它使得HTTP傳輸的不僅是普通的文本,而變得豐富多彩。
每個MIME類型由兩部分組成,前面是數據的大類別,例如聲音audio、圖象p_w_picpath等,後面定義具體的種類。
常見的MIME類型
超文本標記語言文本 .html text/html
xml文檔 .xml text/xml
XHTML文檔 .xhtml application/xhtml+xml
普通文本 .txt text/plain
RTF文本 .rtf application/rtf
PDF文檔 .pdf application/pdf
Microsoft Word文件 .word application/msword
PNG圖像 .png p_w_picpath/png
GIF圖形 .gif p_w_picpath/gif
JPEG圖形 .jpeg,.jpg p_w_picpath/jpeg
au聲音文件 .au audio/basic
MIDI音樂文件 mid,.midi audio/midi,audio/x-midi
RealAudio音樂文件 .ra, .ram audio/x-pn-realaudio
MPEG文件 .mpg,.mpeg video/mpeg
AVI文件 .avi video/x-msvideo
GZIP文件 .gz application/x-gzip
TAR文件 .tar application/x-tar
任意的二進制數據 application/octet-stream
Internet中有一個專門組織IANA來確認標準的MIME類型,但Internet發展的太快,很多應用程序等不及IANA來確認他們使用的MIME類型爲標準類型。因此他們使用在類別中以x-開頭的方法標識這個類別還沒有成爲標準,例如:x-gzip,x-tar等。事實上這些類型運用的很廣泛,已經成爲了事實標準。只要客戶機和服務器共同承認這個MIME類型,即使它是不標準的類型也沒有關係,客戶程序就能根據MIME類型,採用具體的處理手段來處理數據。而Web服務器和瀏覽器(包括操作系統)中,缺省都設置了標準的和常見的MIME類型,只有對於不常見的 MIME類型,才需要同時設置服務器和客戶瀏覽器,以進行識別。
由於MIME類型與文檔的後綴相關,因此服務器使用文檔的後綴來區分不同文件的MIME類型,服務器中必須定義文檔後綴和MIME類型之間的對應關係。而客戶程序從服務器上接收數據的時候,它只是從服務器接受數據流,並不瞭解文檔的名字,因此服務器必須使用附加信息來告訴客戶程序數據的MIME類型。服務器在發送真正的數據之前,就要先發送標誌數據的MIME類型的信息,這個信息使用Content-type關鍵字進行定義,例如對於HTML文檔,服務器將首先發送以下兩行MIME標識信息,這個標識並不是真正的數據文件的一部分。
Content-type: text/html
注意,第二行爲一個空行,這是必須的,使用這個空行的目的是將MIME信息與真正的數據內容分隔開。
MIME利用了一個事實就是,RFC 822在消息體的內容中做了一點限制:唯一的限制就是隻能使用簡單的ASCII文本。所以,MIME信息由正常的Internet文本郵件組成,文本郵件擁有一些特別的符合RFC 822的信息頭和格式化過的信息體(用ASCII 的子集來表示的附件)。這些MIME頭給出了一種在郵件中表示附件的特別的方法。
MIME信息的剖析
一個普通的文本郵件的信息包含一個頭部分(To: From: Subject: 等等)和一個體部分(Hello Mr.,等等)。在一個符合MIME的信息中,也包含一個信息頭並不奇怪,郵件的各個部分叫做MIME段,每段前也綴以一個特別的頭。MIME郵件只是基於RFC 822郵件的一個擴展。然而它有着自己的RFC規範集。
頭字段
MIME頭根據在郵件包中的位置,大體上分爲MIME信息頭和MIME段頭。(譯者:MIME信息頭指整個郵件的頭,而MIME段頭只每個MIME段的頭。)
MIME信息頭有:
MIME-Version:
這個頭提供了所用MIME的版本號。這個值習慣上爲1.0。
Content-Type:
它定義了數據的類型,以便數據能被適當的處理。有效的類型有:text,
p_w_picpath,audio,video, applications,multipart和message。注意任何一個二進制附件都應該被叫做application/octet- stream。這個頭的一些用例爲:p_w_picpath/jpg, application/mswork,multipart/mixed,這只是很少的一部分。
Content-Transfer-Encoding:
這是所有頭中最重要的一個,因爲它說明了對數據所執行的編碼方式,客
戶/MUA 將用它對附件進行解碼。對於每個附件,可以使用7bit,8bit,
binary ,quoted-printable,base64和custom中的一種編碼方式。7bit編碼是用在US ASCII字符集上的常用的一種編碼方式,也就是,保持它的原樣。8bit和binary編碼一般不用。對人類可讀的標準文本,如果傳輸要經過對格式有影響的網關時對其進行保護,可以使用quoted printable 。Base64是一種通用方法,在需要決定使用哪一種編碼方法時,它提供了一個不用費腦子的選擇;它通常用在二進制,非文本數據上。注意,任何非7bit 數據必須用一種模式編碼,這樣它就可以通過Internet郵件網關!
Content-ID:
如果Content-Type是message/external-body或multipart/alternative時,這個
頭就有用了。它超出了本文的範圍。
Content-Description:
這是一個可選的頭。它是任何信息段內容的自由文本描述。描述必須使用us-ascii碼。
Content-Disposition:
一個試驗性的頭,它用於給客戶程序/MUA提供提示,來決定是否在行內顯示附件或作爲單獨的附件。
MIME段頭(出現在實際的MIME附件部分的頭),除了MIME-Version頭,可以擁有以上任何頭字段。如果一個MIME頭是信息塊的一部分,它將作用於整個信息體。例如,如果Content-Transfer-Encoding顯示在信息(指整個信息)頭中,它應用於整個信息體,但是如果它顯示在一個MIME段裏,它"只能"用於那個段中.
注意:其可以對自動對收到的郵件進行解密
編輯本段
MIME類型大全
格式前面爲後輟名,後面爲對應的MIME型(例如:rar application/x-rar-compressed 表示.RAR對應的是application/x-rar-compressed )
application/vnd.lotus-1-2-3
3gp video/3gpp
aab application/x-authoware-bin
aam application/x-authoware-map
aas application/x-authoware-seg
ai application/postscript
aif audio/x-aiff
aifc audio/x-aiff
aiff audio/x-aiff
als audio/X-Alpha5
amc application/x-mpeg
ani application/octet-stream
asc text/plain
asd application/astound
asf video/x-ms-asf
asn application/astound
asp application/x-asap
asx video/x-ms-asf
au audio/basic
avb application/octet-stream
avi video/x-msvideo
awb audio/amr-wb
bcpio application/x-bcpio
bin application/octet-stream
bld application/bld
bld2 application/bld2
bmp application/x-MS-bmp
bpk application/octet-stream
bz2 application/x-bzip2
cal p_w_picpath/x-cals
ccn application/x-cnc
cco application/x-cocoa
cdf application/x-netcdf
cgi magnus-internal/cgi
chat application/x-chat
class application/octet-stream
clp application/x-msclip
cmx application/x-cmx
co application/x-cult3d-object
cod p_w_picpath/cis-cod
cpio application/x-cpio
cpt application/mac-compactpro
crd application/x-mscardfile
csh application/x-csh
csm chemical/x-csml
csml chemical/x-csml
css text/css
cur application/octet-stream
dcm x-lml/x-evm
dcr application/x-director
dcx p_w_picpath/x-dcx
dhtml text/html
dir application/x-director
dll application/octet-stream
dmg application/octet-stream
dms application/octet-stream
doc application/msword
dot application/x-dot
dvi application/x-dvi
dwf drawing/x-dwf
dwg application/x-autocad
dxf application/x-autocad
dxr application/x-director
ebk application/x-expandedbook
emb chemical/x-embl-dl-nucleotide
embl chemical/x-embl-dl-nucleotide
eps application/postscript
epub application/epub+zip
eri p_w_picpath/x-eri
es audio/echospeech
esl audio/echospeech
etc application/x-earthtime
etx text/x-setext
evm x-lml/x-evm
evy application/x-envoy
exe application/octet-stream
fh4 p_w_picpath/x-freehand
fh5 p_w_picpath/x-freehand
fhc p_w_picpath/x-freehand
fif p_w_picpath/fif
fm application/x-maker
fpx p_w_picpath/x-fpx
fvi video/isivideo
gau chemical/x-gaussian-input
gca application/x-gca-compressed
gdb x-lml/x-gdb
gif p_w_picpath/gif
gps application/x-gps
gtar application/x-gtar
gz application/x-gzip
hdf application/x-hdf
hdm text/x-hdml
hdml text/x-hdml
hlp application/winhlp
hqx application/mac-binhex40
htm text/html
html text/html
hts text/html
ice x-conference/x-cooltalk
ico application/octet-stream
ief p_w_picpath/ief
ifm p_w_picpath/gif
ifs p_w_picpath/ifs
imy audio/melody
ins application/x-NET-Install
ips application/x-ipscript
ipx application/x-ipix
it audio/x-mod
itz audio/x-mod
ivr i-world/i-vrml
j2k p_w_picpath/j2k
jad text/vnd.sun.j2me.app-descriptor
jam application/x-jam
jar application/java-archive
jnlp application/x-java-jnlp-file
jpe p_w_picpath/jpeg
jpeg p_w_picpath/jpeg
jpg p_w_picpath/jpeg
jpz p_w_picpath/jpeg
js application/x-javascript
jwc application/jwc
kjx application/x-kjx
lak x-lml/x-lak
latex application/x-latex
lcc application/fastman
lcl application/x-digitalloca
lcr application/x-digitalloca
lgh application/lgh
lha application/octet-stream
lml x-lml/x-lml
lmlpack x-lml/x-lmlpack
lsf video/x-ms-asf
lsx video/x-ms-asf
lzh application/x-lzh
m13 application/x-msmediaview
m14 application/x-msmediaview
m15 audio/x-mod
m3u audio/x-mpegurl
m3url audio/x-mpegurl
ma1 audio/ma1
ma2 audio/ma2
ma3 audio/ma3
ma5 audio/ma5
man application/x-troff-man
map magnus-internal/p_w_picpathmap
mbd application/mbedlet
mct application/x-mascot
mdb application/x-msaccess
mdz audio/x-mod
me application/x-troff-me
mel text/x-vmel
mi application/x-mif
mid audio/midi
midi audio/midi
mif application/x-mif
mil p_w_picpath/x-cals
mio audio/x-mio
mmf application/x-skt-lbs
mng video/x-mng
mny application/x-msmoney
moc application/x-mocha
mocha application/x-mocha
mod audio/x-mod
mof application/x-yumekara
mol chemical/x-mdl-molfile
mop chemical/x-mopac-input
mov video/quicktime
movie video/x-sgi-movie
mp2 audio/x-mpeg
mp3 audio/x-mpeg
mp4 video/mp4
mpc application/vnd.mpohun.certificate
mpe video/mpeg
mpeg video/mpeg
mpg video/mpeg
mpg4 video/mp4
mpga audio/mpeg
mpn application/vnd.mophun.application
mpp application/vnd.ms-project
mps application/x-mapserver
mrl text/x-mrml
mrm application/x-mrm
ms application/x-troff-ms
mts application/metastream
mtx application/metastream
mtz application/metastream
mzv application/metastream
nar application/zip
nbmp p_w_picpath/nbmp
nc application/x-netcdf
ndb x-lml/x-ndb
ndwn application/ndwn
nif application/x-nif
nmz application/x-scream
nokia-op-logo p_w_picpath/vnd.nok-oplogo-color
npx application/x-netfpx
nsnd audio/nsnd
nva application/x-neva1
oda application/oda
oom application/x-AtlasMate-Plugin
pac audio/x-pac
pae audio/x-epac
pan application/x-pan
pbm p_w_picpath/x-portable-bitmap
pcx p_w_picpath/x-pcx
pda p_w_picpath/x-pda
pdb chemical/x-pdb
pdf application/pdf
pfr application/font-tdpfr
pgm p_w_picpath/x-portable-graymap
pict p_w_picpath/x-pict
pm application/x-perl
pmd application/x-pmd
png p_w_picpath/png
pnm p_w_picpath/x-portable-anymap
pnz p_w_picpath/png
pot application/vnd.ms-powerpoint
ppm p_w_picpath/x-portable-pixmap
pps application/vnd.ms-powerpoint
ppt application/vnd.ms-powerpoint
pqf application/x-cprplayer
pqi application/cprplayer
prc application/x-prc
proxy application/x-ns-proxy-autoconfig
ps application/postscript
ptlk application/listenup
pub application/x-mspublisher
pvx video/x-pv-pvx
qcp audio/vnd.qcelp
qt video/quicktime
qti p_w_picpath/x-quicktime
qtif p_w_picpath/x-quicktime
r3t text/vnd.rn-realtext3d
ra audio/x-pn-realaudio
ram audio/x-pn-realaudio
rar application/x-rar-compressed
ras p_w_picpath/x-cmu-raster
rdf application/rdf+xml
rf p_w_picpath/vnd.rn-realflash
rgb p_w_picpath/x-rgb
rlf application/x-richlink
rm audio/x-pn-realaudio
rmf audio/x-rmf
rmm audio/x-pn-realaudio
rmvb audio/x-pn-realaudio
rnx application/vnd.rn-realplayer
roff application/x-troff
rp p_w_picpath/vnd.rn-realpix
rpm audio/x-pn-realaudio-plugin
rt text/vnd.rn-realtext
rte x-lml/x-gps
rtf application/rtf
rtg application/metastream
rtx text/richtext
rv video/vnd.rn-realvideo
rwc application/x-rogerwilco
s3m audio/x-mod
s3z audio/x-mod
sca application/x-supercard
scd application/x-msschedule
sdf application/e-score
sea application/x-stuffit
sgm text/x-sgml
sgml text/x-sgml
sh application/x-sh
shar application/x-shar
shtml magnus-internal/parsed-html
shw application/presentations
si6 p_w_picpath/si6
si7 p_w_picpath/vnd.stiwap.sis
si9 p_w_picpath/vnd.lgtwap.sis
sis application/vnd.symbian.install
sit application/x-stuffit
skd application/x-Koan
skm application/x-Koan
skp application/x-Koan
skt application/x-Koan
slc application/x-salsa
smd audio/x-smd
smi application/smil
smil application/smil
smp application/studiom
smz audio/x-smd
snd audio/basic
spc text/x-speech
spl application/futuresplash
spr application/x-sprite
sprite application/x-sprite
sdp application/sdp
spt application/x-spt
src application/x-wais-source
stk application/hyperstudio
stm audio/x-mod
sv4cpio application/x-sv4cpio
sv4crc application/x-sv4crc
svf p_w_picpath/vnd
svg p_w_picpath/svg-xml
svh p_w_picpath/svh
svr x-world/x-svr
swf application/x-shockwave-flash
swfl application/x-shockwave-flash
t application/x-troff
tad application/octet-stream
talk text/x-speech
tar application/x-tar
taz application/x-tar
tbp application/x-timbuktu
tbt application/x-timbuktu
tcl application/x-tcl
tex application/x-tex
texi application/x-texinfo
texinfo application/x-texinfo
tgz application/x-tar
thm application/vnd.eri.thm
tif p_w_picpath/tiff
tiff p_w_picpath/tiff
tki application/x-tkined
tkined application/x-tkined
toc application/toc
toy p_w_picpath/toy
tr application/x-troff
trk x-lml/x-gps
trm application/x-msterminal
tsi audio/tsplayer
tsp application/dsptype
tsv text/tab-separated-values
tsv text/tab-separated-values
ttf application/octet-stream
ttz application/t-time
txt text/plain
ult audio/x-mod
ustar application/x-ustar
uu application/x-uuencode
uue application/x-uuencode
vcd application/x-cdlink
vcf text/x-vcard
vdo video/vdo
vib audio/vib
viv video/vivo
vivo video/vivo
vmd application/vocaltec-media-desc
vmf application/vocaltec-media-file
vmi application/x-dreamcast-vms-info
vms application/x-dreamcast-vms
vox audio/voxware
vqe audio/x-twinvq-plugin
vqf audio/x-twinvq
vql audio/x-twinvq
vre x-world/x-vream
vrml x-world/x-vrml
vrt x-world/x-vrt
vrw x-world/x-vream
vts workbook/formulaone
wav audio/x-wav
wax audio/x-ms-wax
wbmp p_w_picpath/vnd.wap.wbmp
web application/vnd.xara
wi p_w_picpath/wavelet
wis application/x-InstallShield
wm video/x-ms-wm
wma audio/x-ms-wma
wmd application/x-ms-wmd
wmf application/x-msmetafile
wml text/vnd.wap.wml
wmlc application/vnd.wap.wmlc
wmls text/vnd.wap.wmlscript
wmlsc application/vnd.wap.wmlscriptc
wmlscript text/vnd.wap.wmlscript
wmv video/x-ms-wmv
wmx video/x-ms-wmx
wmz application/x-ms-wmz
wpng p_w_picpath/x-up-wpng
wpt x-lml/x-gps
wri application/x-mswrite
wrl x-world/x-vrml
wrz x-world/x-vrml
ws text/vnd.wap.wmlscript
wsc application/vnd.wap.wmlscriptc
wv video/wavelet
wvx video/x-ms-wvx
wxl application/x-wxl
x-gzip application/x-gzip
xar application/vnd.xara
xbm p_w_picpath/x-xbitmap
xdm application/x-xdma
xdma application/x-xdma
xdw application/vnd.fujixerox.docuworks
xht application/xhtml+xml
xhtm application/xhtml+xml
xhtml application/xhtml+xml
xla application/vnd.ms-excel
xlc application/vnd.ms-excel
xll application/x-excel
xlm application/vnd.ms-excel
xls application/vnd.ms-excel
xlt application/vnd.ms-excel
xlw application/vnd.ms-excel
xm audio/x-mod
xml text/xml
xmz audio/x-mod
xpi application/x-xpinstall
xpm p_w_picpath/x-xpixmap
xsit text/xml
xsl text/xml
xul text/xul
xwd p_w_picpath/x-xwindowdump
xyz chemical/x-pdb
yz1 application/x-yz1
z application/x-compress
zac application/x-zaurus-zac
zip application/zip