RFC 2936
HTTP MIME Type Handler Detection
RFC 2936: HTTP MIME Type Handler Detection 🎀
okay bestie, this is RFC 2936 from the Network Working Group 💅 It was written by D. Eastlake (Motorola), C. Smith (Royal Bank of Canada), and D. Soroka (IBM), and published in September 2000. It's an Informational doc, so it's giving "here's some helpful info" and not "here's a rule you must follow." It doesn't list anything it obsoletes or updates, so it's just vibing on its own ✨
Status of This Memo ✨
This memo gives information to the Internet community. It is not an Internet standard of any kind 🌸 Distribution is unlimited, so share it with whoever needs it 🫶
Copyright Notice 💜
Copyright (C) The Internet Society (2000). All Rights Reserved.
Abstract 🦋
Okay so the whole problem is this: people building web pages that offer services over the Hypertext Transfer Protocol (HTTP) often have no idea which Multipurpose Internet Mail Extensions (MIME) types have handlers installed in the user's browser 😭 Stuff like the Internet Open Trading Protocol (IOTP), VRML, SET, or some streaming media handler might or might not be there. Sometimes they'd love to show different pages or content based on whether a handler is available, and that's the vibe this doc is about 🎀
This doc sums up reasonable techniques for solving that, for most of the browsers that were actually out on the Internet in early 2000. It's meant to be practically useful for implementers during the time before wide deployment of superior standards-based techniques that might get developed later 🧚
Acknowledgements 🫶
Helpful comments from Tony Lewis of Visa were incorporated, so thank you Tony 💖
Table of Contents 🍓
1. Introduction................................................. 2
2. The HTTP 'Accept' Header..................................... 2
3. JavaScript................................................... 3
4. ActiveX and the Windows Registry............................. 4
5. ECML, The Electronic Commerce Modeling Language.............. 4
6. Putting It All Together...................................... 5
7. Future Development........................................... 5
8. Security Considerations...................................... 5
9. IANA Considerations.......................................... 6
References...................................................... 6
Appendix A: Browser Version Sniffer Code........................ 8
Authors' Addresses.............................................. 12
Full Copyright Statement........................................ 131. Introduction 🌈
Entities building web pages to provide services over [HTTP] frequently have the problem of not knowing which [MIME] types have handlers installed in a user's browser. For example, whether an [IOTP] or VRML or [SET] or some streaming media handler is available. In lots of cases they'd want to show different pages or content depending on whether a MIME handler is there 👀 Sending a response with a MIME type that isn't supported can totally derail the user experience. The browser pops up asking what to do with the data, and the behavior that would have happened with the right handler installed just doesn't happen 😭
This document describes reasonable techniques to solve this for most of the browsers actually deployed on the Internet as of early 2000. It's meant to be practically useful for implementers during the period before wide deployment of superior standards-based techniques that may be developed. It's written in terms of figuring out whether a handler for application/iotp or application/x-iotp exists, but it works just as well for other MIME types 💅
2. The HTTP 'Accept' Header 💖
The problem should be solved by the Hyper Text Transport Protocol [HTTP] request Accept header, which lists the accepted [MIME] types. This header is present in both Version 1.0 and 1.1 of HTTP, and its content is supposed to be a list of MIME types and subtypes that are accepted. The only catch is that many browsers just send */* or something similar 🙈
If the particular MIME type you're looking for is specifically present in the Accept header, it's generally safe to assume a handler for it is actually installed or built into the browser ✨
NOTE: Not the main topic here, but if you're designing MIME type handler software and you have access to a browser interface that lets you request that your MIME types get inserted into the Accept header, you generally should do that 🔥 It makes it way easier for servers that care about that MIME type to respond correctly.
3. JavaScript 🧚
Most recent browsers support one or more scripting languages, and the most widely deployed one is "JavaScript". These scripting languages live inside web pages and let you run interpreted programming constructs that can poke at the browser environment, conditionally change what page content gets displayed, and so on 🌸 For example, Appendix A shows JavaScript from the Netscape web site that figures out which operating system, browser, and version a web page is showing up in.
NOTE: JavaScript is a trademark of SUN Microsystems, Inc. It was originally called LiveScript. It has nothing to do with the Java language. 💀
The syntax for script use looks like an HTML comment, so browsers that don't support scripting just ignore it. Basically, script use starts with <!-- and ends with --> 🦋 Here's a simple example of conditionally running parts of a web page based on JavaScript MIME type handler detection:
<SCRIPT LANGUAGE=JAVASCRIPT>
<!-- hide it
if (navigator.mimeTypes && navigator.mimeTypes.length > 0) {
if ( navigator.mimeTypes["application/iotp"] ||
navigator.mimeTypes["application/x-iotp"]) {
// here if IOTP handler exists
}
else {
// here if IOTP handler does not exist
}
}
// end and hide -->
</SCRIPT>That's the first three parts done, bestie! 🌈👑
References 📚✨
Okay bestie, here's the reading list 🤓 Every single one of these is cited earlier in the spec, so don't skip any of them 💅
- [ECML] Eastlake, D. and T. Goldstein, "ECML v1: Field Names for E-Commerce", RFC 2706, October 1999.
- [HTTP] Berners-Lee, T., Fielding, R. and H. Frystyk, "Hypertext Transfer Protocol -- HTTP/1.0", RFC 1945, May 1996.
- [HTTP] Fielding, R., Gettys, J., Mogul, J., Frystyk, H., Masinter, L., Leach, P. and T. Berners-Lee, "Hypertext Transfer Protocol -- HTTP/1.1", RFC 2616, June 1999.
- [IOTP] Burdett, D., "Internet Open Trading Protocol - IOTP Version 1.0", RFC 2801, April 2000.
- [MIME] Freed, N. and N. Borenstein, "Multipurpose Internet Mail Extensions (MIME) Part One: Format of Internet Message Bodies", RFC 2045, November 1996.
- [MIME] Freed, N. and N. Borenstein, "Multipurpose Internet Mail Extensions (MIME) Part Two: Media Types", RFC 2046, November 1996.
- [MIME] Moore, K., "MIME (Multipurpose Internet Mail Extensions) Part Three: Message Header Extensions for Non-ASCII Text", RFC 2047, November 1996.
- [MIME] Freed, N., Klensin, J. and J. Postel, "Multipurpose Internet Mail Extensions (MIME) Part Four: Registration Procedures", RFC 2048, November 1996.
- [SET] "Secure Electronic Transaction (SET) Specification, Version 1.0", May 31, 1997, available from
<http://www.setco.org>.- Book 1: Business Description
- Book 2: Programmer's Guide
- Book 3: Formal Protocol Definition
- [TLS] Dierks, T. and C. Allen, "The TLS Protocol Version 1.0", RFC 2246, January 1999.
- [W3C] World Wide Web Consortium,
<www.w3.org>
Appendix A: Browser Version Sniffer Code 🕵️♀️🌈
Now for the spicy bit 🔥 This is the JavaScript that sniffs out which browser, version, and OS someone is using. It's from Netscape (1999) and it's giving very "everything you always wanted to know about your client but were afraid to ask" 😭 Netscape gave permission to reuse and distribute it, and the comments are full of warnings like "don't use is_nav4 when you mean is_nav4up" 💀 Read them, they're iconic.
<SCRIPT LANGUAGE="JavaScript">
<!-- hide JavaScript from non-JavaScript browsers
// Ultimate client-side JavaScript client sniff.
// (C) Netscape Communications 1999.
// Permission granted to reuse and distribute.
// Revised 17 May 99 to add is_nav5up and is_ie5up (see below).
// Everything you always wanted to know about your JavaScript client
// but were afraid to ask. Creates "is_" variables indicating:
// (1) browser vendor:
// is_nav, is_ie, is_opera
// (2) browser version number:
// is_major (integer indicating major version number: 2, 3, 4 ...)
// is_minor (float indicating full version number:
// 2.02, 3.01, 4.04 ...)
// (3) browser vendor AND major version number
// is_nav2, is_nav3, is_nav4, is_nav4up, is_nav5, is_nav5up,
// is_ie3, is_ie4, is_ie4up
// (4) JavaScript version number:
// is_js (float indicating full JavaScript version number:
// 1, 1.1, 1.2 ...)
// (5) OS platform and version:
// is_win, is_win16, is_win32, is_win31,
// is_win95, is_winnt, is_win98
// is_os2
// is_mac, is_mac68k, is_macppc
// is_unix
// is_sun, is_sun4, is_sun5, is_suni86
// is_irix, is_irix5, is_irix6
// is_hpux, is_hpux9, is_hpux10
// is_aix, is_aix1, is_aix2, is_aix3, is_aix4
// is_linux, is_sco, is_unixware, is_mpras, is_reliant
// is_dec, is_sinix, is_freebsd, is_bsd
// is_vms
//
// See http://www.it97.de/JavaScript/JS_tutorial/bstat/navobj.html and
// http://www.it97.de/JavaScript/JS_tutorial/bstat/Browseraol.html
// for detailed lists of userAgent strings.
//
// Note: you don't want your Nav4 or IE4 code to "turn off" or
// stop working when Nav5 and IE5 (or later) are released, so
// in conditional code forks, use is_nav4up ("Nav4 or greater")
// and is_ie4up ("IE4 or greater") instead of is_nav4 or is_ie4
// to check version in code which you want to work on future
// versions.
// convert all characters to lowercase to simplify testing
var agt=navigator.userAgent.toLowerCase();
// *** BROWSER VERSION ***
// Note: On IE5, these return 4, so use is_ie5up to detect IE5.
var is_major = parseInt(navigator.appVersion);
var is_minor = parseFloat(navigator.appVersion);
// Note: Opera and WebTV spoof Navigator. We do strict client
// detection. If you want to allow spoofing, take out the tests
// for opera and webtv.
var is_nav = ((agt.indexOf('mozilla')!=-1)
&& (agt.indexOf('spoofer')==-1)
&& (agt.indexOf('compatible') == -1)
&& (agt.indexOf('opera')==-1)
&& (agt.indexOf('webtv')==-1));
var is_nav2 = (is_nav && (is_major == 2));
var is_nav3 = (is_nav && (is_major == 3));
var is_nav4 = (is_nav && (is_major == 4));
var is_nav4up = (is_nav && (is_major >= 4));
var is_navonly = (is_nav && ((agt.indexOf(";nav") != -1) ||
(agt.indexOf("; nav") != -1)) );
var is_nav5 = (is_nav && (is_major == 5));
var is_nav5up = (is_nav && (is_major >= 5));
var is_ie = (agt.indexOf("msie") != -1);
var is_ie3 = (is_ie && (is_major < 4));
var is_ie4 = (is_ie && (is_major == 4)
&& (agt.indexOf("msie 5.0")==-1) );
var is_ie4up = (is_ie && (is_major >= 4));
var is_ie5 = (is_ie && (is_major == 4)
&& (agt.indexOf("msie 5.0")!=-1) );
var is_ie5up = (is_ie && !is_ie3 && !is_ie4);
// KNOWN BUG: On AOL4, returns false if IE3 is embedded browser
// or if this is the first browser window opened. Thus the
// variables is_aol, is_aol3, and is_aol4 aren't 100% reliable.
var is_aol = (agt.indexOf("aol") != -1);
var is_aol3 = (is_aol && is_ie3);
var is_aol4 = (is_aol && is_ie4);
var is_opera = (agt.indexOf("opera") != -1);
var is_webtv = (agt.indexOf("webtv") != -1);
// *** JAVASCRIPT VERSION CHECK ***
var is_js;
if (is_nav2 || is_ie3) is_js = 1.0
else if (is_nav3 || is_opera) is_js = 1.1
else if ((is_nav4 && (is_minor <= 4.05)) || is_ie4) is_js = 1.2
else if ((is_nav4 && (is_minor > 4.05)) || is_ie5) is_js = 1.3
else if (is_nav5) is_js = 1.4
// NOTE: In the future, update this code when newer versions of JS
// are released. For now, we try to provide some upward compatibility
// so that future versions of Nav and IE will show they are at
// *least* JS 1.x capable. Always check for JS version compatibility
// with > or >=.
else if (is_nav && (is_major > 5)) is_js = 1.4
else if (is_ie && (is_major > 5)) is_js = 1.3
// HACK: no idea for other browsers;
// always check for JS version with > or >=
else is_js = 0.0;
// *** PLATFORM ***
var is_win = ( (agt.indexOf("win")!=-1) ||
(agt.indexOf("16bit")!=-1) );
// NOTE: On Opera 3.0, the userAgent string includes "Windows 95/NT4"
// on all Win32, so you can't distinguish between Win95 and WinNT.
var is_win95 = ((agt.indexOf("win95")!=-1) ||
(agt.indexOf("windows 95")!=-1));
// is this a 16 bit compiled version?
var is_win16 = ((agt.indexOf("win16")!=-1) ||
(agt.indexOf("16bit")!=-1) ||
(agt.indexOf("windows 3.1")!=-1) ||
(agt.indexOf("windows 16-bit")!=-1) );
var is_win31 = ((agt.indexOf("windows 3.1")!=-1) ||
(agt.indexOf("win16")!=-1) ||
(agt.indexOf("windows 16-bit")!=-1));
// NOTE: Reliable detection of Win98 may not be possible.
// It appears that:
// - On Nav 4.x and before you'll get plain "Windows" in userAgent.
// - On Mercury client, the 32-bit version will return "Win98", but
// the 16-bit version running on Win98 will still return "Win95".
var is_win98 = ((agt.indexOf("win98")!=-1) ||
(agt.indexOf("windows 98")!=-1));
var is_winnt = ((agt.indexOf("winnt")!=-1) ||
(agt.indexOf("windows nt")!=-1));
var is_win32 = (is_win95 || is_winnt || is_win98 ||
((is_major >= 4) &&
(navigator.platform == "Win32")) ||
(agt.indexOf("win32")!=-1) ||
(agt.indexOf("32bit")!=-1));
var is_os2 = ((agt.indexOf("os/2")!=-1) ||
(navigator.appVersion.indexOf("OS/2")!=-1) ||
(agt.indexOf("ibm-webexplorer")!=-1));
var is_mac = (agt.indexOf("mac")!=-1);
var is_mac68k = (is_mac && ((agt.indexOf("68k")!=-1) ||
(agt.indexOf("68000")!=-1)));
var is_macppc = (is_mac && ((agt.indexOf("ppc")!=-1) ||
(agt.indexOf("powerpc")!=-1)));
var is_sun = (agt.indexOf("sunos")!=-1);
var is_sun4 = (agt.indexOf("sunos 4")!=-1);
var is_sun5 = (agt.indexOf("sunos 5")!=-1);
var is_suni86= (is_sun && (agt.indexOf("i86")!=-1));
var is_irix = (agt.indexOf("irix") !=-1); // SGI
var is_irix5 = (agt.indexOf("irix 5") !=-1);
var is_irix6 = ((agt.indexOf("irix 6") !=-1) ||
(agt.indexOf("irix6") !=-1));
var is_hpux = (agt.indexOf("hp-ux")!=-1);
var is_hpux9 = (is_hpux && (agt.indexOf("09.")!=-1));
var is_hpux10= (is_hpux && (agt.indexOf("10.")!=-1));
var is_aix = (agt.indexOf("aix") !=-1); // IBM
var is_aix1 = (agt.indexOf("aix 1") !=-1);
var is_aix2 = (agt.indexOf("aix 2") !=-1);
var is_aix3 = (agt.indexOf("aix 3") !=-1);
var is_aix4 = (agt.indexOf("aix 4") !=-1);
var is_linux = (agt.indexOf("inux")!=-1);
var is_sco = (agt.indexOf("sco")!=-1) ||
(agt.indexOf("unix_sv")!=-1);
var is_unixware = (agt.indexOf("unix_system_v")!=-1);
var is_mpras = (agt.indexOf("ncr")!=-1);
var is_reliant = (agt.indexOf("reliantunix")!=-1);
var is_dec = ((agt.indexOf("dec")!=-1) ||
(agt.indexOf("osf1")!=-1) ||
(agt.indexOf("dec_alpha")!=-1) ||
(agt.indexOf("alphaserver")!=-1) ||
(agt.indexOf("ultrix")!=-1) ||
(agt.indexOf("alphastation")!=-1));
var is_sinix = (agt.indexOf("sinix")!=-1);
var is_freebsd = (agt.indexOf("freebsd")!=-1);
var is_bsd = (agt.indexOf("bsd")!=-1);
var is_unix = ((agt.indexOf("x11")!=-1) || is_sun ||
is_irix || is_hpux ||
is_sco ||is_unixware || is_mpras || is_reliant ||
is_dec || is_sinix || is_aix || is_linux ||
is_bsd || is_freebsd);
var is_vms = ((agt.indexOf("vax")!=-1) ||
(agt.indexOf("openvms")!=-1));
</SCRIPT>Authors' Addresses 💌
Last but not least, the people who wrote this thing 🫶 Here's how to reach each of them, in their own words 💖
Donald E. Eastlake 3rd
Motorola
140 Forest Avenue
Hudson, MA 01749 USA
Phone: +1 978-562-2827(h)
+1 508-261-5434(w)
Fax: +1 508-261-4447(w)
EMail: Donald.Eastlake@motorola.com
Chris J. Smith
Royal Bank of Canada
277 Front Street West
Toronto, Ontario M5V 3A4 CANADA
Phone: +1 416-348-6090
Fax: +1 416-348-2210
EMail: chris.smith@royalbank.com
David M. Soroka
IBM
Raleigh, NC
Phone: +1 919-486-2684
Fax: +1 919-543-4653
EMail: dsoroka@us.ibm.comFull Copyright Statement 💖
Okay bestie, the legal bit, but make it cute. 🎀 The Internet Society owns the copyright on this one, and it's (2000) and All Rights Reserved 💅 That's the headline.
Here's the good news. You're allowed to copy and share this document, and you can translate it too 🌈 You can also write derivative works that comment on it, explain it, or help people implement it, and you can publish and distribute those however you like 🦋 Whole thing or just a chunk, no restrictions of any kind ✨ The one condition is that the copyright notice and this paragraph have to stay on every copy and every derivative work 🫶
What you can't do is change this document itself. No removing the copyright notice, no scrubbing out the references to the Internet Society or other Internet organizations 😭 The exceptions are: you're using it to develop Internet standards (then you have to follow the copyright procedures in the Internet Standards process 📜), or you're translating it into a language that isn't English 🌸
The permissions are perpetual, meaning they never expire, and the Internet Society, its successors, and its assigns can't take them back 💜 Forever and ever, bestie. 👑
Now the part that's a little less fun. This document and everything in it is provided "AS IS", and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. 💀 So no promises that it won't step on anyone's rights, and no promises that it's sellable or fits your exact purpose. Read it, use it, but don't expect a guarantee. 🙈
Acknowledgement 🍓
Last one, and it's a sweet one 🧚 Funding for the RFC Editor function is currently provided by the Internet Society 🫶 Thank you to the folks keeping the lights on for the RFC Editor! 🌈✨
📦 where this page comes from
- ietf: rfc2936 2000-09
- 💖 girlified by claude-haiku-5-5 on : a language model's rewrite of the original, under its terms