RFC 4229

HTTP Header Field Registrations

📅 published December 2005, from ietf

HTTP Header Field Registrations 🎀

okay bestie, this is RFC 4229 and it's giving registry paperwork energy, but it's actually important 💅✨ Here's the tea: it's an Informational RFC from the Network Working Group, which means it's sharing info for the Internet community. It is not an Internet standard, so no pressure to treat it like one 🙈

The authors are M. Nottingham and J. Mogul, both from HP Labs. The document is dated December 2005 🍓 Its title is "HTTP Header Field Registrations." The title block doesn't list anything it obsoletes or updates, so it doesn't replace or change any older RFC, which is iconic of it 🧚

Status of This Memo ✨

so the big disclaimer 💜 This memo gives info to the Internet community. It is not specifying an Internet standard of any kind. And you're free to share it, because distribution is unlimited 🦋

Copyright Notice 🌸

Abstract 🔥

okay so this doc does two things 👑 First, it sets up the starting contents of a permanent IANA registry for HTTP header fields. Second, it sets up a provisional repository for HTTP header fields too. Both of these are described in RFC 3864 💖

Table of Contents 🌈

here's the whole table of contents, verbatim so you can see how everything is numbered and nested (the numbers are what the text uses to point at other sections, so they matter 🫶)

   1. Introduction ....................................................4
   2. Registration Templates ..........................................4
      2.1. Permanent HTTP Header Field Registrations ..................5
         2.1.1. Header field: A-IM ....................................7
         2.1.2. Header field: Accept ..................................8
         2.1.3. Header field: Accept-Additions ........................8
         2.1.4. Header field: Accept-Charset ..........................8
         2.1.5. Header field: Accept-Encoding .........................9
         2.1.6. Header field: Accept-Features .........................9
         2.1.7. Header field: Accept-Language .........................9
         2.1.8. Header field: Accept-Ranges ..........................10
         2.1.9. Header field: Age ....................................10
         2.1.10. Header field: Allow .................................10
         2.1.11. Header field: Alternates ............................10
         2.1.12. Header field: Authentication-Info ...................11
         2.1.13. Header field: Authorization .........................11
         2.1.14. Header field: C-Ext .................................11
         2.1.15. Header field: C-Man .................................12
         2.1.16. Header field: C-Opt .................................12
         2.1.17. Header field: C-PEP .................................12
         2.1.18. Header field: C-PEP-Info ............................13
         2.1.19. Header field: Cache-Control .........................13
         2.1.20. Header field: Connection ............................13
         2.1.21. Header field: Content-Base ..........................14
         2.1.22. Header field: Content-Disposition ...................14
         2.1.23. Header field: Content-Encoding ......................14
         2.1.24. Header field: Content-ID ............................14
         2.1.25. Header field: Content-Language ......................15
         2.1.26. Header field: Content-Length ........................15
         2.1.27. Header field: Content-Location ......................15
         2.1.28. Header field: Content-MD5 ...........................16
         2.1.29. Header field: Content-Range .........................16
         2.1.30. Header field: Content-Script-Type ...................16
         2.1.31. Header field: Content-Style-Type ....................17
         2.1.32. Header field: Content-Type ..........................17
         2.1.33. Header field: Content-Version .......................17
         2.1.34. Header field: Cookie ................................17
         2.1.35. Header field: Cookie2 ...............................18
         2.1.36. Header field: DAV ...................................18
         2.1.37. Header field: Date ..................................18
         2.1.38. Header field: Default-Style .........................19
         2.1.39. Header field: Delta-Base ............................19
         2.1.40. Header field: Depth .................................19
         2.1.41. Header field: Derived-From ..........................19
         2.1.42. Header field: Destination ...........................20
         2.1.43. Header field: Differential-ID .......................20
         2.1.44. Header field: Digest ................................20
         2.1.45. Header field: ETag ..................................21
         2.1.46. Header field: Expect ................................21
         2.1.47. Header field: Expires ...............................21
         2.1.48. Header field: Ext ...................................22
         2.1.49. Header field: From ..................................22
         2.1.50. Header field: GetProfile ............................22
         2.1.51. Header field: Host ..................................23
         2.1.52. Header field: IM ....................................23
         2.1.53. Header field: If ....................................23
         2.1.54. Header field: If-Match ..............................23
         2.1.55. Header field: If-Modified-Since .....................24
         2.1.56. Header field: If-None-Match .........................24
         2.1.57. Header field: If-Range ..............................24
         2.1.58. Header field: If-Unmodified-Since ...................25
         2.1.59. Header field: Keep-Alive ............................25
         2.1.60. Header field: Label .................................25
         2.1.61. Header field: Last-Modified .........................25
         2.1.62. Header field: Link ..................................26
         2.1.63. Header field: Location ..............................26
         2.1.64. Header field: Lock-Token ............................26
         2.1.65. Header field: MIME-Version ..........................27
         2.1.66. Header field: Man ...................................27
         2.1.67. Header field: Max-Forwards ..........................27
         2.1.68. Header field: Meter .................................27
         2.1.69. Header field: Negotiate .............................28
         2.1.70. Header field: Opt ...................................28
         2.1.71. Header field: Ordering-Type .........................28
         2.1.72. Header field: Overwrite .............................29
         2.1.73. Header field: P3P ...................................29
         2.1.74. Header field: PEP ...................................29
         2.1.75. Header field: PICS-Label ............................30
         2.1.76. Header field: Pep-Info ..............................30
         2.1.77. Header field: Position ..............................30
         2.1.78. Header field: Pragma ................................31
         2.1.79. Header field: ProfileObject .........................31
         2.1.80. Header field: Protocol ..............................31
         2.1.81. Header field: Protocol-Info .........................32
         2.1.82. Header field: Protocol-Query ........................32
         2.1.83. Header field: Protocol-Request ......................32
         2.1.84. Header field: Proxy-Authenticate ....................32
         2.1.85. Header field: Proxy-Authentication-Info .............33
         2.1.86. Header field: Proxy-Authorization ...................33
         2.1.87. Header field: Proxy-Features ........................33
         2.1.88. Header field: Proxy-Instruction .....................34
         2.1.89. Header field: Public ................................34
         2.1.90. Header field: Range .................................34
         2.1.91. Header field: Referer ...............................34
         2.1.92. Header field: Retry-After ...........................35
         2.1.93. Header field: Safe ..................................35
         2.1.94. Header field: Security-Scheme .......................35
         2.1.95. Header field: Server ................................36
         2.1.96. Header field: Set-Cookie ............................36
         2.1.97. Header field: Set-Cookie2 ...........................36
         2.1.98. Header field: SetProfile ............................36
         2.1.99. Header field: SoapAction ............................37
         2.1.100. Header field: Status-URI ...........................37
         2.1.101. Header field: Surrogate-Capability .................38
         2.1.102. Header field: Surrogate-Control ....................38
         2.1.103. Header field: TCN ..................................38
         2.1.104. Header field: TE ...................................39
         2.1.105. Header field: Timeout ..............................39
         2.1.106. Header field: Trailer ..............................39
         2.1.107. Header field: Transfer-Encoding ....................39
         2.1.108. Header field: URI ..................................40
         2.1.109. Header field: Upgrade ..............................40
         2.1.110. Header field: User-Agent ...........................40
         2.1.111. Header field: Variant-Vary .........................41
         2.1.112. Header field: Vary .................................41
         2.1.113. Header field: Via ..................................41
         2.1.114. Header field: WWW-Authenticate .....................41
         2.1.115. Header field: Want-Digest ..........................42
         2.1.116. Header field: Warning ..............................42

      2.2. Provisional HTTP Header Field Submissions .................43
         2.2.1. Header field: Compliance .............................43
         2.2.2. Header field: Content-Transfer-Encoding ..............43
         2.2.3. Header field: Cost ...................................44
         2.2.4. Header field: Message-ID .............................44
         2.2.5. Header field: Non-Compliance .........................44
         2.2.6. Header field: Optional ...............................44
         2.2.7. Header field: Resolution-Hint ........................45
         2.2.8. Header field: Resolver-Location ......................45
         2.2.9. Header field: SubOK ..................................46
         2.2.10. Header field: Subst .................................46
         2.2.11. Header field: Title .................................46
         2.2.12. Header field: UA-Color ..............................46
         2.2.13. Header field: UA-Media ..............................47
         2.2.14. Header field: UA-Pixels .............................47
         2.2.15. Header field: UA-Resolution .........................48
         2.2.16. Header field: UA-Windowpixels .......................48
         2.2.17. Header field: Version ...............................48
   3. IANA Considerations ............................................49
   4. Security Considerations ........................................49
   5. Acknowledgements ...............................................49
   6. Informative References .........................................49

part 1 of 6 is done 🧚💜 the actual body of the RFC (sections 1 through 6, including all the registrations) is coming in the next parts, so stay tuned, bestie 🫶

1. Introduction 🎀

okay so bestie, HTTP/1.0 [3] and HTTP/1.1 [11] both define protocol constructs, namely the HTTP-header and message-header BNF rules, and those are what get used as message headers 💅. These specs also define a bunch of HTTP headers themselves, and they leave room for extension through new field-names 🌸

This document sets up the initial contents of an IANA registry for permanent HTTP header field-names, plus an IANA repository for provisional ones ✨ Both are run under Registration Procedures for Message Header Fields [1], so it's all very official and very organized 🫶

Quick heads up: neither one tracks the syntax or semantics of field-values 🙈 Also, some headers act differently depending on where they show up (Cache-Control in requests vs. responses is the classic example), but both registries still treat the HTTP header field-name namespace as one singular thing 💜

And, ngl, some of the contact details listed might be outdated by now 💀

2. Registration Templates 💅

Header field entries get summarized in a table so they're easy to scan, and then the full details come later in the sections below 🦋

2.1. Permanent HTTP Header Field Registrations 🌈

Header name             Protocol
-----------             --------
A-IM                      http
Accept                    http
Accept-Additions          http
Accept-Charset            http
Accept-Encoding           http
Accept-Features           http
Accept-Language           http
Accept-Ranges             http
Age                       http
Allow                     http
Alternates                http
Authentication-Info       http
Authorization             http
C-Ext                     http
C-Man                     http
C-Opt                     http
C-PEP                     http
C-PEP-Info                http
Cache-Control             http
Connection                http
Content-Base              http
Content-Disposition       http
Content-Encoding          http
Content-ID                http
Content-Language          http
Content-Length            http
Content-Location          http
Content-MD5               http
Content-Range             http
Content-Script-Type       http
Content-Style-Type        http
Content-Type              http
Content-Version           http
Cookie                    http
Cookie2                   http
DAV                       http
Date                      http
Default-Style             http
Delta-Base                http
Depth                     http
Derived-From              http
Destination               http
Differential-ID           http
Digest                    http
ETag                      http
Expect                    http
Expires                   http
Ext                       http
From                      http
GetProfile                http
Host                      http
IM                        http
If                        http
If-Match                  http
If-Modified-Since         http
If-None-Match             http
If-Range                  http
If-Unmodified-Since       http
Keep-Alive                http
Label                     http
Last-Modified             http
Link                      http
Location                  http
Lock-Token                http
MIME-Version              http
Man                       http
Max-Forwards              http
Meter                     http
Negotiate                 http
Opt                       http
Ordering-Type             http
Overwrite                 http
P3P                       http
PEP                       http
PICS-Label                http
Pep-Info                  http
Position                  http
Pragma                    http
ProfileObject             http
Protocol                  http
Protocol-Info             http
Protocol-Query            http
Protocol-Request          http
Proxy-Authenticate        http
Proxy-Authentication-Info http
Proxy-Authorization       http
Proxy-Features            http
Proxy-Instruction         http
Public                    http
Range                     http
Referer                   http
Retry-After               http
Safe                      http
Security-Scheme           http
Server                    http
Set-Cookie                http
Set-Cookie2               http
SetProfile                http
SoapAction                http
Status-URI                http
Surrogate-Capability      http
Surrogate-Control         http
TCN                       http
TE                        http
Timeout                   http
Trailer                   http
Transfer-Encoding         http
URI                       http
Upgrade                   http
User-Agent                http
Variant-Vary              http
Vary                      http
Via                       http
WWW-Authenticate          http
Want-Digest               http
Warning                   http

2.1.1. Header field: A-IM ✨

Applicable protocol: http [11]
Status: standard
Author/change controller:
- IETF (iesg@ietf.org)
- Internet Engineering Task Force
Specification document(s): RFC3229 [16]

2.1.2. Header field: Accept 🌸

Applicable protocol: http [11]
Status: standard
Author/change controller:
- IETF (iesg@ietf.org)
- Internet Engineering Task Force
Specification document(s): RFC2616 [11]

2.1.3. Header field: Accept-Additions 🙈

Applicable protocol: http [11]
Status: informational
Author/change controller:
- IETF (iesg@ietf.org)
- Internet Engineering Task Force
Specification document(s): RFC2324 [9]
Related information: spoof

2.1.4. Header field: Accept-Charset 💖

Applicable protocol: http [11]
Status: standard
Author/change controller:
- IETF (iesg@ietf.org)
- Internet Engineering Task Force
Specification document(s): RFC2616 [11]

2.1.5. Header field: Accept-Encoding 🦋

Applicable protocol: http [11]
Status: standard
Author/change controller:
- IETF (iesg@ietf.org)
- Internet Engineering Task Force
Specification document(s): RFC2616 [11]

2.1.6. Header field: Accept-Features 🧚

Applicable protocol: http [11]
Status: experimental
Author/change controller:
- Andrew H. Mutz (mutz@hpl.hp.com)
- Koen Holtman (koen@win.tue.nl)
Specification document(s): RFC2295 [7]

2.1.7. Header field: Accept-Language 🌈

Applicable protocol: http [11]
Status: standard
Author/change controller:
- IETF (iesg@ietf.org)
- Internet Engineering Task Force
Specification document(s): RFC2616 [11]

2.1.8. Header field: Accept-Ranges ⭐

Applicable protocol: http [11]
Status: standard
Author/change controller:
- IETF (iesg@ietf.org)
- Internet Engineering Task Force
Specification document(s): RFC2616 [11]

2.1.9. Header field: Age 🍓

Applicable protocol: http [11]
Status: standard
Author/change controller:
- IETF (iesg@ietf.org)
- Internet Engineering Task Force
Specification document(s): RFC2616 [11]

2.1.10. Header field: Allow 👑

Applicable protocol: http [11]
Status: standard
Author/change controller:
- IETF (iesg@ietf.org)
- Internet Engineering Task Force
Specification document(s): RFC2616 [11]

2.1.11. Header field: Alternates 🔥

Applicable protocol: http [11]
Status: experimental
Author/change controller:
- Andrew H. Mutz (mutz@hpl.hp.com)
- Koen Holtman (koen@win.tue.nl)
Specification document(s): RFC2295 [7]

2.1.12. Header field: Authentication-Info 🫶

Applicable protocol: http [11]
Status: standard
Author/change controller:
- IETF (iesg@ietf.org)
- Internet Engineering Task Force
Specification document(s): RFC2617 [12]

2.1.13. Header field: Authorization 💜

Applicable protocol: http [11]
Status: standard
Author/change controller:
- IETF (iesg@ietf.org)
- Internet Engineering Task Force
Specification document(s): RFC2616 [11]

2.1.14. Header field: C-Ext ✨

Applicable protocol: http [11]
Status: experimental
Author/change controller:
- Henrik Frystyk Nielsen (frystyk@microsoft.com)
- Paul J. Leach (paulle@microsoft.com)
- Scott Lawrence (lawrence@agranat.com)
Specification document(s): RFC2774 [14]

2.1.15. Header field: C-Man 🎀

Applicable protocol: http [11]
Status: experimental
Author/change controller:
- Henrik Frystyk Nielsen (frystyk@microsoft.com)
- Paul J. Leach (paulle@microsoft.com)
- Scott Lawrence (lawrence@agranat.com)
Specification document(s): RFC2774 [14]

2.1.16. Header field: C-Opt 🦋

Applicable protocol: http [11]
Status: experimental
Author/change controller:
- Henrik Frystyk Nielsen (frystyk@microsoft.com)
- Paul J. Leach (paulle@microsoft.com)
- Scott Lawrence (lawrence@agranat.com)
Specification document(s): RFC2774 [14]

2.1.17. Header field: C-PEP 🌸

Applicable protocol: http [11]
Status: deprecated
Author/change controller:
- Henrik Frystyk Nielsen (frystyk@w3.org)
- World Wide Web Consortium, MIT Laboratory for Computer Science
- Dan Connolly (connolly@w3.org)
- World Wide Web Consortium, MIT Laboratory for Computer Science
- Rohit Khare (khare@w3.org)
- World Wide Web Consortium, MIT Laboratory for Computer Science
- Eric Prud'hommeaux (eric@w3.org)
- World Wide Web Consortium, MIT Laboratory for Computer Science
Specification document(s): PEP [29]

2.1.18. Header field: C-PEP-Info 🌈

Applicable protocol: http [11]
Status: deprecated
Author/change controller:
- Henrik Frystyk Nielsen (frystyk@w3.org)
- World Wide Web Consortium, MIT Laboratory for Computer Science
- Dan Connolly (connolly@w3.org)
- World Wide Web Consortium, MIT Laboratory for Computer Science
- Rohit Khare (khare@w3.org)
- World Wide Web Consortium, MIT Laboratory for Computer Science
- Eric Prud'hommeaux (eric@w3.org)
- World Wide Web Consortium, MIT Laboratory for Computer Science
Specification document(s): PEP [29]

2.1.19. Header field: Cache-Control 💅

Applicable protocol: http [11]
Status: standard
Author/change controller:
- IETF (iesg@ietf.org)
- Internet Engineering Task Force
Specification document(s): RFC2616 [11]

2.1.20. Header field: Connection 🫶

Applicable protocol: http [11]
Status: standard
Author/change controller:
- IETF (iesg@ietf.org)
- Internet Engineering Task Force
Specification document(s): RFC2616 [11]

2.1.21. Header field: Content-Base 🍓

Applicable protocol: http [11]
Status: standard
Author/change controller:
- IETF (iesg@ietf.org)
- Internet Engineering Task Force
Specification document(s): RFC2068 [4]

2.1.22. Header field: Content-Disposition ⭐

Applicable protocol: http [11]
Status: standard
Author/change controller:
- IETF (iesg@ietf.org)
- Internet Engineering Task Force
Specification document(s): RFC2616 [11]

2.1.23. Header field: Content-Encoding 💖

Applicable protocol: http [11]
Status: standard
Author/change controller:
- IETF (iesg@ietf.org)
- Internet Engineering Task Force
Specification document(s): RFC2616 [11]

2.1.24. Header field: Content-ID 🎀

okay so this one is a whole group project 🫶 the authors are listed as a crew from Marimba, Netscape, Sun, Novell, and At Home, and the spec lives in DRP [20]. it's informational, not standard, so think of it as a friendly note rather than a rule 💅

Applicable protocol: http [11]

Status: informational
Author/change controller:
   Arthur van Hoff  (avh@marimba.com)
   Marimba Inc.
   John Giannandrea  (jg@netscape.com)
   Netscape Inc.
   Mark Hapner  (mark.hapner@sun.com)
   Sun Microsystems Inc.
   Steve Carter  (srcarter@novell.com)
   Novell Inc.
   Milo Medin  (medin@home.net)
   At Home Corp

Specification document(s):
   DRP [20]

2.1.25. Header field: Content-Language 🌸

this one is standard, which means it's a proper IETF thing, handled by the IESG and the Internet Engineering Task Force, and it's specced in RFC2616 [11] 🦋

Applicable protocol: http [11]

Status: standard

Author/change controller:
   IETF  (iesg@ietf.org)
   Internet Engineering Task Force

Specification document(s):
   RFC2616 [11]

2.1.26. Header field: Content-Length 💖

the classic. standard, IETF-run, and it lives in RFC2616 [11] 🍓 literally a core fixture of the web

Applicable protocol: http [11]

Status: standard

Author/change controller:
   IETF  (iesg@ietf.org)
   Internet Engineering Task Force

Specification document(s):
   RFC2616 [11]

2.1.27. Header field: Content-Location ✨

standard again, IETF again, RFC2616 [11] again 🧚 she's consistent, I'll give her that

Applicable protocol: http [11]

Status: standard
Author/change controller:
   IETF  (iesg@ietf.org)
   Internet Engineering Task Force

Specification document(s):
   RFC2616 [11]

2.1.28. Header field: Content-MD5 🔥

standard, IETF, RFC2616 [11]. the name sounds like a hash, and it's giving secure vibes, but I'm only telling you what the registry says here 🙈

Applicable protocol: http [11]

Status: standard

Author/change controller:
   IETF  (iesg@ietf.org)
   Internet Engineering Task Force

Specification document(s):
   RFC2616 [11]

2.1.29. Header field: Content-Range 🦋

standard, IETF, RFC2616 [11]. it pairs with the range stuff, which is very iconic of it 💅

Applicable protocol: http [11]

Status: standard

Author/change controller:
   IETF  (iesg@ietf.org)
   Internet Engineering Task Force

Specification document(s):
   RFC2616 [11]

2.1.30. Header field: Content-Script-Type 🌈

this one comes from the W3C, not the IETF, which is a fun little crossover 🫶 it's standard and it's specced in HTML 4 [21]

Applicable protocol: http [11]

Status: standard

Author/change controller:
   W3C  (web-human@w3.org)
   World Wide Web Consortium

Specification document(s):
   HTML 4 [21]

2.1.31. Header field: Content-Style-Type 💜

same W3C energy as the one before it, also standard, also HTML 4 [21] 🎀 they really said "let's make a matching set" and I respect it

Applicable protocol: http [11]

Status: standard

Author/change controller:
   W3C  (web-human@w3.org)
   World Wide Web Consortium

Specification document(s):
   HTML 4 [21]

2.1.32. Header field: Content-Type ⭐

the main character of the Content-* family 👑 standard, IETF, RFC2616 [11]. she's everywhere

Applicable protocol: http [11]

Status: standard

Author/change controller:
   IETF  (iesg@ietf.org)
   Internet Engineering Task Force

Specification document(s):
   RFC2616 [11]

2.1.33. Header field: Content-Version 🧚

standard, IETF, but this one is specced in RFC2068 [4] instead of RFC2616. it's an older one, so she's got some history 🌸

Applicable protocol: http [11]

Status: standard

Author/change controller:
   IETF  (iesg@ietf.org)
   Internet Engineering Task Force

Specification document(s):
   RFC2068 [4]

okay cookies, obviously iconic 🍪 standard, IETF, and it's specced in RFC2965 [15]. the spec doc is the important bit here, so bookmark it 🔖

Applicable protocol: http [11]

Status: standard
Author/change controller:
   IETF  (iesg@ietf.org)
   Internet Engineering Task Force

Specification document(s):
   RFC2965 [15]

2.1.35. Header field: Cookie2 🦋

the sequel nobody asked for but everyone needed 💅 standard, IETF, RFC2965 [15]. same spec, different header, very sibling energy

Applicable protocol: http [11]

Status: standard

Author/change controller:
   IETF  (iesg@ietf.org)
   Internet Engineering Task Force

Specification document(s):
   RFC2965 [15]

2.1.36. Header field: DAV 💖

standard, IETF, and it's specced in RFC2518 [10] 🌈 the name is short but she's doing a lot 🫶

Applicable protocol: http [11]

Status: standard

Author/change controller:
   IETF  (iesg@ietf.org)
   Internet Engineering Task Force

Specification document(s):
   RFC2518 [10]

2.1.37. Header field: Date ✨

standard, IETF, RFC2616 [11]. timestamps are lowkey the most important thing on the internet, fr 🕰️

Applicable protocol: http [11]

Status: standard

Author/change controller:
   IETF  (iesg@ietf.org)
   Internet Engineering Task Force

Specification document(s):
   RFC2616 [11]

2.1.38. Header field: Default-Style 🌸

W3C back again, standard, and it's specced in HTML 4 [21] 🎀 she's the quiet one of the style-type girls

Applicable protocol: http [11]

Status: standard

Author/change controller:
   W3C  (web-human@w3.org)
   World Wide Web Consortium

Specification document(s):
   HTML 4 [21]

2.1.39. Header field: Delta-Base 💜

standard, IETF, and it's specced in RFC3229 [16] 🔥 it's all about deltas, which is giving "only send what changed" energy, and I'm obsessed

Applicable protocol: http [11]

Status: standard

Author/change controller:
   IETF  (iesg@ietf.org)
   Internet Engineering Task Force

Specification document(s):
   RFC3229 [16]

2.1.40. Header field: Depth 🧚

standard, IETF, RFC2518 [10]. the name is literally what it sounds like, so no mystery here 🫶

Applicable protocol: http [11]

Status: standard

Author/change controller:
   IETF  (iesg@ietf.org)
   Internet Engineering Task Force

Specification document(s):
   RFC2518 [10]

2.1.41. Header field: Derived-From 🌈

standard, IETF, RFC2068 [4]. she's got roots in the older spec, like a family tree 🌳

Applicable protocol: http [11]

Status: standard
Author/change controller:
   IETF  (iesg@ietf.org)
   Internet Engineering Task Force

Specification document(s):
   RFC2068 [4]

2.1.42. Header field: Destination ⭐

standard, IETF, RFC2518 [10]. where it's going, bestie 🦋 it's giving GPS for your requests

Applicable protocol: http [11]

Status: standard

Author/change controller:
   IETF  (iesg@ietf.org)
   Internet Engineering Task Force

Specification document(s):
   RFC2518 [10]

2.1.43. Header field: Differential-ID 💅

this one is informational, from the same DRP crew as Content-ID, with the same authors and the same spec, DRP [20] 🫶 it's the sibling who got the same group chat invite

Applicable protocol: http [11]

Status: informational

Author/change controller:
   Arthur van Hoff  (avh@marimba.com)
   Marimba Inc.
   John Giannandrea  (jg@netscape.com)
   Netscape Inc.
   Mark Hapner  (mark.hapner@sun.com)
   Sun Microsystems Inc.
   Steve Carter  (srcarter@novell.com)
   Novell Inc.
   Milo Medin  (medin@home.net)
   At Home Corp

Specification document(s):
   DRP [20]

2.1.44. Header field: Digest 🔥

standard, IETF, and it's specced in RFC3230 [17] 🍓 she's ready to hash things out, literally

Applicable protocol: http [11]

Status: standard
Author/change controller:
   IETF  (iesg@ietf.org)
   Internet Engineering Task Force

Specification document(s):
   RFC3230 [17]

2.1.45. Header field: ETag 💖

standard, IETF, RFC2616 [11]. the tag is the vibe check for a resource, and it's iconic 🏷️✨

Applicable protocol: http [11]

Status: standard

Author/change controller:
   IETF  (iesg@ietf.org)
   Internet Engineering Task Force

Specification document(s):
   RFC2616 [11]

2.1.46. Header field: Expect 🌸

standard, IETF, RFC2616 [11]. she's kind of a planner, always expecting something 🧚

Applicable protocol: http [11]

Status: standard

Author/change controller:
   IETF  (iesg@ietf.org)
   Internet Engineering Task Force

Specification document(s):
   RFC2616 [11]

2.1.47. Header field: Expires 🎀

standard, IETF, RFC2616 [11]. this one is dramatic in the best way, like a timer on a story 😭

Applicable protocol: http [11]

Status: standard

Author/change controller:
   IETF  (iesg@ietf.org)
   Internet Engineering Task Force

Specification document(s):
   RFC2616 [11]

2.1.48. Header field: Ext 🦋

this one is experimental, which means it's still in its era of trying new things 🧪 the authors are Henrik Frystyk Nielsen, Paul J. Leach, and Scott Lawrence, and the spec is RFC2774 [14] 💜

Applicable protocol: http [11]

Status: experimental

Author/change controller:
   Henrik Frystyk Nielsen  (frystyk@microsoft.com)
   Paul J. Leach  (paulle@microsoft.com)
   Scott Lawrence  (lawrence@agranat.com)

Specification document(s):
   RFC2774 [14]

2.1.49. Header field: From 💅

standard, IETF, RFC2616 [11]. it's giving "who sent this" and that's a whole main character question 👑

Applicable protocol: http [11]

Status: standard

Author/change controller:
   IETF  (iesg@ietf.org)
   Internet Engineering Task Force

Specification document(s):
   RFC2616 [11]

2.1.50. Header field: GetProfile 🌈

this one is informational, from Pat Hensley, Max Metral, Upendra Shardanand, Donna Converse, and Mike Myers, with their companies listed in the template. the spec is OPS over HTTP [22] 🧚 it's a little side project with a big crew

Applicable protocol: http [11]

Status: informational

Author/change controller:
   Pat Hensley  (hensley@firefly.net)
   FireFly Network, Inc.
   Max Metral  (max@firefly.net)
   FireFly Network, Inc.
   Upendra Shardanand  (shard@firefly.net)
   FireFly Network, Inc.
   Donna Converse  (converse@netscape.com)
   Netscape Communications
   Mike Myers  (mmyers@verisign.com)
   Verisign, Inc.

Specification document(s):
   OPS over HTTP [22]

2.1.51. Header field: Host ⭐

standard, IETF, RFC2616 [11]. she tells the server exactly who she wants to talk to, and that's the whole point of her 🏠💖

Applicable protocol: http [11]

Status: standard

Author/change controller:
   IETF  (iesg@ietf.org)
   Internet Engineering Task Force

Specification document(s):
   RFC2616 [11]

2.1.52. Header field: IM 🍓

standard, IETF, and it's specced in RFC3229 [16] 🫶 very short name, very big delta energy

Applicable protocol: http [11]

Status: standard

Author/change controller:
   IETF  (iesg@ietf.org)
   Internet Engineering Task Force

Specification document(s):
   RFC3229 [16]

2.1.53. Header field: If 🔥

standard, IETF, RFC2518 [10]. the conditional queen, she only does things if the vibes are right 👑

Applicable protocol: http [11]

Status: standard

Author/change controller:
   IETF  (iesg@ietf.org)
   Internet Engineering Task Force

Specification document(s):
   RFC2518 [10]

2.1.54. Header field: If-Match 🧚

standard, IETF, RFC2616 [11]. she's the strict one: only proceed if it matches, bestie 🌸

Applicable protocol: http [11]

Status: standard
Author/change controller:
   IETF  (iesg@ietf.org)
   Internet Engineering Task Force

Specification document(s):
   RFC2616 [11]

2.1.55. Header field: If-Modified-Since 🎀

standard, IETF, RFC2616 [11]. she checks whether anything has changed since a certain time, which is very "did you update your story" 💜

Applicable protocol: http [11]

Status: standard

Author/change controller:
   IETF  (iesg@ietf.org)
   Internet Engineering Task Force

Specification document(s):
   RFC2616 [11]

2.1.56. Header field: If-None-Match 🦋

standard, IETF, RFC2616 [11]. the opposite energy of If-Match, and I'm lowkey obsessed with the duo 💅

Applicable protocol: http [11]

Status: standard

Author/change controller:
   IETF  (iesg@ietf.org)
   Internet Engineering Task Force

Specification document(s):
   RFC2616 [11]

2.1.57. Header field: If-Range 🌈

standard, IETF, RFC2616 [11]. she only cares about the range if the thing hasn't changed, so she's very specific 🫶

Applicable protocol: http [11]

Status: standard

Author/change controller:
   IETF  (iesg@ietf.org)
   Internet Engineering Task Force

Specification document(s):
   RFC2616 [11]

2.1.58. Header field: If-Unmodified-Since 💖

standard, IETF, RFC2616 [11]. the name is long, but the energy is "only if nothing changed since then" 🕰️ literally a whole sentence in one header

Applicable protocol: http [11]

Status: standard

Author/change controller:
   IETF  (iesg@ietf.org)
   Internet Engineering Task Force

Specification document(s):
   RFC2616 [11]

2.1.59. Header field: Keep-Alive 🌸

standard, IETF, and it's specced in RFC2068 [4] 🍓 she wants the conversation to keep going, which is honestly so relatable

Applicable protocol: http [11]

Status: standard

Author/change controller:
   IETF  (iesg@ietf.org)
   Internet Engineering Task Force

Specification document(s):
   RFC2068 [4]

2.1.60. Header field: Label 🧚

standard, IETF, and it's specced in RFC3253 [18] 🏷️ she's the one who makes everything easy to find

Applicable protocol: http [11]

Status: standard

Author/change controller:
   IETF  (iesg@ietf.org)
   Internet Engineering Task Force

Specification document(s):
   RFC3253 [18]

2.1.61. Header field: Last-Modified 🔥

standard, IETF, RFC2616 [11]. the "when did this last get touched" header, which is very "I was just thinking about you" 🫶

Applicable protocol: http [11]

Status: standard
Author/change controller:
   IETF  (iesg@ietf.org)
   Internet Engineering Task Force

Specification document(s):
   RFC2616 [11]

2.1.62. Header field: Link 🌈

standard, IETF, and it's specced in RFC2068 [4] 🦋 she connects things, which is giving main character networking

Applicable protocol: http [11]

Status: standard

Author/change controller:
   IETF  (iesg@ietf.org)
   Internet Engineering Task Force

Specification document(s):
   RFC2068 [4]

2.1.63. Header field: Location 💜

standard, IETF, RFC2616 [11]. she's the one who says "no, go over HERE instead" 📍✨

Applicable protocol: http [11]

Status: standard

Author/change controller:
   IETF  (iesg@ietf.org)
   Internet Engineering Task Force

Specification document(s):
   RFC2616 [11]

2.1.64. Header field: Lock-Token 🍓

standard, IETF, RFC2518 [10]. it's the little key that proves you've got the lock, and that's iconic 🔐💅

Applicable protocol: http [11]

Status: standard

Author/change controller:
   IETF  (iesg@ietf.org)
   Internet Engineering Task Force

Specification document(s):
   RFC2518 [10]

2.1.65. Header field: MIME-Version 🎀

standard, IETF, RFC2616 [11]. she's got the MIME vibes, very old-school but still in the group chat 🧚

Applicable protocol: http [11]

Status: standard

Author/change controller:
   IETF  (iesg@ietf.org)
   Internet Engineering Task Force

Specification document(s):
   RFC2616 [11]

2.1.66. Header field: Man 🌸

this one is experimental, same crew as Ext, with Henrik Frystyk Nielsen, Paul J. Leach, and Scott Lawrence, and the spec is RFC2774 [14] 🧪 she's the sibling still figuring out her thing 💖

Applicable protocol: http [11]

Status: experimental

Author/change controller:
   Henrik Frystyk Nielsen  (frystyk@microsoft.com)
   Paul J. Leach  (paulle@microsoft.com)
   Scott Lawrence  (lawrence@agranat.com)

Specification document(s):
   RFC2774 [14]

2.1.67. Header field: Max-Forwards 🦋

standard, IETF, RFC2616 [11]. she keeps track of how many hops are left, so nothing goes on forever 🔥 very responsible energy

Applicable protocol: http [11]

Status: standard

Author/change controller:
   IETF  (iesg@ietf.org)
   Internet Engineering Task Force

Specification document(s):
   RFC2616 [11]

2.1.68. Header field: Meter 🌈

standard, IETF, and it's specced in RFC2227 [6] 💅 she's the one measuring everything, and honestly she's giving data queen

Applicable protocol: http [11]

Status: standard
Author/change controller:
   IETF  (iesg@ietf.org)
   Internet Engineering Task Force

Specification document(s):
   RFC2227 [6]

2.1.69. Header field: Negotiate ✨

this one is experimental, from Andrew H. Mutz and Koen Holtman, and it's specced in RFC2295 [7] 🧪 she's still negotiating her whole personality, and that's valid 🫶

Applicable protocol: http [11]

Status: experimental

Author/change controller:
   Andrew H. Mutz  (mutz@hpl.hp.com)
   Koen Holtman  (koen@win.tue.nl)

Specification document(s):
   RFC2295 [7]

2.1.70. Header field: Opt ✨

Applicable protocol: http [11] 🎀

Status: experimental 🧪

Author/change controller:

Henrik Frystyk Nielsen (frystyk@microsoft.com) 💖
Paul J. Leach (paulle@microsoft.com) 💖
Scott Lawrence (lawrence@agranat.com) 💖

Specification document(s):

RFC2774 [14] 📜

2.1.71. Header field: Ordering-Type 🦋

Applicable protocol: http [11] 🎀

Status: standard ✅

Author/change controller:

IETF (iesg@ietf.org) 💜
Internet Engineering Task Force 💜

Specification document(s):

RFC3648 [19] 📜

2.1.72. Header field: Overwrite 🌸

Applicable protocol: http [11] 🎀

Status: standard ✅

Author/change controller:

IETF (iesg@ietf.org) 💜
Internet Engineering Task Force 💜

Specification document(s):

RFC2518 [10] 📜

2.1.73. Header field: P3P 🌈

Applicable protocol: http [11] 🎀

Status: standard ✅

Author/change controller:

W3C (web-human@w3.org) 💜
World Wide Web Consortium 💜

Specification document(s):

P3P [23] 📜

2.1.74. Header field: PEP 🍓

Applicable protocol: http [11] 🎀

Status: deprecated 💀

Author/change controller:

Henrik Frystyk Nielsen (frystyk@w3.org) 💖
World Wide Web Consortium, MIT Laboratory for Computer Science 💖
Dan Connolly (connolly@w3.org) 💖
World Wide Web Consortium, MIT Laboratory for Computer Science 💖
Rohit Khare (khare@w3.org) 💖
World Wide Web Consortium, MIT Laboratory for Computer Science 💖
Eric Prud'hommeaux (eric@w3.org) 💖
World Wide Web Consortium, MIT Laboratory for Computer Science 💖

Specification document(s):

PEP [29] 📜

2.1.75. Header field: PICS-Label 🧚

Applicable protocol: http [11] 🎀

Status: standard ✅

Author/change controller:

W3C (web-human@w3.org) 💜
World Wide Web Consortium 💜

Specification document(s):

PICSLabels [24] 📜

2.1.76. Header field: Pep-Info 🙈

Applicable protocol: http [11] 🎀

Status: deprecated 💀

Author/change controller:

Henrik Frystyk Nielsen (frystyk@w3.org) 💖
World Wide Web Consortium, MIT Laboratory for Computer Science 💖
Dan Connolly (connolly@w3.org) 💖
World Wide Web Consortium, MIT Laboratory for Computer Science 💖
Rohit Khare (khare@w3.org) 💖
World Wide Web Consortium, MIT Laboratory for Computer Science 💖
Eric Prud'hommeaux (eric@w3.org) 💖
World Wide Web Consortium, MIT Laboratory for Computer Science 💖

Specification document(s): PEP [29] 📜

2.1.77. Header field: Position 🫶

Applicable protocol: http [11] 🎀

Status: standard ✅

Author/change controller:

IETF (iesg@ietf.org) 💜
Internet Engineering Task Force 💜

Specification document(s):

RFC3648 [19] 📜

2.1.78. Header field: Pragma 💅

Applicable protocol: http [11] 🎀

Status: standard ✅

Author/change controller:

IETF (iesg@ietf.org) 💜
Internet Engineering Task Force 💜

Specification document(s):

RFC2616 [11] 📜

2.1.79. Header field: ProfileObject 👑

Applicable protocol: http [11] 🎀

Status: informational ℹ️

Author/change controller:

Pat Hensley (hensley@firefly.net) 💖
FireFly Network, Inc. 💖
Max Metral (max@firefly.net) 💖
FireFly Network, Inc. 💖
Upendra Shardanand (shard@firefly.net) 💖
FireFly Network, Inc. 💖
Donna Converse (converse@netscape.com) 💖
Netscape Communications 💖
Mike Myers (mmyers@verisign.com) 💖
Verisign, Inc. 💖

Specification document(s):

OPS over HTTP [22] 📜

2.1.80. Header field: Protocol 🌸

Applicable protocol: http [11] 🎀

Status: standard ✅

Author/change controller:

W3C (web-human@w3.org) 💜
World Wide Web Consortium 💜

Specification document(s):

PICSLabels [24] 📜

2.1.81. Header field: Protocol-Info 🦋

Applicable protocol: http [11] 🎀

Status: deprecated 💀

Author/change controller:

Don Eastlake (dee@cybercash.com) 💖
Rohit Khare (khare@w3.org) 💖
Jim Miller (jmiller@w3.org) 💖

Specification document(s):

Selecting Payment Mechanisms [26] 📜

2.1.82. Header field: Protocol-Query 🍓

Applicable protocol: http [11] 🎀

Status: deprecated 💀

Author/change controller:

Don Eastlake (dee@cybercash.com) 💖
Rohit Khare (khare@w3.org) 💖
Jim Miller (jmiller@w3.org) 💖

Specification document(s):

Selecting Payment Mechanisms [26] 📜

2.1.83. Header field: Protocol-Request 🌈

Applicable protocol: http [11] 🎀

Status: standard ✅

Author/change controller:

W3C (web-human@w3.org) 💜
World Wide Web Consortium 💜

Specification document(s):

PICSLabels [24] 📜

2.1.84. Header field: Proxy-Authenticate 🔥

Applicable protocol: http [11] 🎀

Status: standard ✅

Author/change controller:

IETF (iesg@ietf.org) 💜
Internet Engineering Task Force 💜

Specification document(s):

RFC2616 [11] 📜

2.1.85. Header field: Proxy-Authentication-Info 🔐

Applicable protocol: http [11] 🎀

Status: standard ✅

Author/change controller:

IETF (iesg@ietf.org) 💜
Internet Engineering Task Force 💜

Specification document(s):

RFC2617 [12] 📜

2.1.86. Header field: Proxy-Authorization 🦋

Applicable protocol: http [11] 🎀

Status: standard ✅

Author/change controller:

IETF (iesg@ietf.org) 💜
Internet Engineering Task Force 💜

Specification document(s):

RFC2616 [11] 📜

2.1.87. Header field: Proxy-Features ✨

Applicable protocol: http [11] 🎀

Status: informational ℹ️

Author/change controller:

Phillip M. Hallam-Baker (hallam@w3.org) 💖
W3C 💖

Specification document(s):

Proxy Notification [27] 📜

2.1.88. Header field: Proxy-Instruction 🌸

Applicable protocol: http [11] 🎀

Status: informational ℹ️

Author/change controller:

Phillip M. Hallam-Baker (hallam@w3.org) 💖
W3C 💖

Specification document(s):

Proxy Notification [27] 📜

2.1.89. Header field: Public 🌈

Applicable protocol: http [11] 🎀

Status: standard ✅

Author/change controller:

IETF (iesg@ietf.org) 💜
Internet Engineering Task Force 💜

Specification document(s):

RFC2068 [4] 📜

2.1.90. Header field: Range 🍓

Applicable protocol: http [11] 🎀

Status: standard ✅

Author/change controller:

IETF (iesg@ietf.org) 💜
Internet Engineering Task Force 💜

Specification document(s):

RFC2616 [11] 📜

2.1.91. Header field: Referer 🧚

Applicable protocol: http [11] 🎀

Status: standard ✅

Author/change controller:

IETF (iesg@ietf.org) 💜
Internet Engineering Task Force 💜

Specification document(s):

RFC2616 [11] 📜

2.1.92. Header field: Retry-After ⭐

Applicable protocol: http [11] 🎀

Status: standard ✅

Author/change controller:

IETF (iesg@ietf.org) 💜
Internet Engineering Task Force 💜

Specification document(s):

RFC2616 [11] 📜

2.1.93. Header field: Safe 🫶

Applicable protocol: http [11] 🎀

Status: experimental 🧪

Author/change controller:

Koen Holtman (koen@win.tue.nl) 💖

Specification document(s):

RFC2310 [8] 📜

2.1.94. Header field: Security-Scheme 🔐

Applicable protocol: http [11] 🎀

Status: experimental 🧪

Author/change controller:

Eric Rescorla (ekr@rtfm.com) 💖
A. Schiffman (ams@terisa.com) 💖

Specification document(s):

RFC2660 [13] 📜

2.1.95. Header field: Server 🖥️

Applicable protocol: http [11] 🎀

Status: standard ✅

Author/change controller:

IETF (iesg@ietf.org) 💜
Internet Engineering Task Force 💜

Specification document(s):

RFC2616 [11] 📜

2.1.96. Header field: Set-Cookie 🍪

Applicable protocol: http [11] 🎀

Status: standard ✅

Author/change controller:

IETF (iesg@ietf.org) 💜
Internet Engineering Task Force 💜

Specification document(s):

RFC2109 [5] 📜

2.1.97. Header field: Set-Cookie2 🍪

Applicable protocol: http [11] 🎀

Status: standard ✅

Author/change controller:

IETF (iesg@ietf.org) 💜
Internet Engineering Task Force 💜

Specification document(s):

RFC2965 [15] 📜

2.1.98. Header field: SetProfile 👑

Applicable protocol: http [11] 🎀

Status: informational ℹ️

Author/change controller:

Pat Hensley (hensley@firefly.net) 💖
FireFly Network, Inc. 💖
Max Metral (max@firefly.net) 💖
FireFly Network, Inc. 💖
Upendra Shardanand (shard@firefly.net) 💖
FireFly Network, Inc. 💖
Donna Converse (converse@netscape.com) 💖
Netscape Communications 💖
Mike Myers (mmyers@verisign.com) 💖
Verisign, Inc. 💖

Specification document(s):

OPS over HTTP [22] 📜

2.1.99. Header field: SoapAction 🧼

Applicable protocol: http [11] 🎀

Status: informational ℹ️

Author/change controller:

Don Box (dbox@develop.com) 💖
DevelopMentor 💖
David Ehnebuske (davide@us.ibm.com) 💖
IBM 💖
Gopal Kakivaya (gopalk@microsoft.com) 💖
Microsoft 💖
Andrew Layman (andrewl@microsoft.com) 💖
Microsoft 💖
Noah Mendelsohn (Noah_Mendelsohn@lotus.com) 💖
Lotus Development Corp. 💖
Hernik Frystyk Nielsen (frystyk@microsoft.com) 💖
Microsoft 💖
Satish Thatte (satisht@microsoft.com) 💖
Microsoft 💖
Dave Winer (dave@userland.com) 💖
UserLand Software, Inc. 💖

Specification document(s):

SOAP [28] 📜

2.1.100. Header field: Status-URI 🚦

Applicable protocol: http [11] 🎀

Status: standard ✅

Author/change controller:

IETF (iesg@ietf.org) 💜
Internet Engineering Task Force 💜

Specification document(s):

RFC2518 [10] 📜

2.1.101. Header field: Surrogate-Capability 🌐

Applicable protocol: http [11] 🎀

Status: informational ℹ️

Author/change controller:

Mark Nottingham (mnot@akamai.com) 💖
Akamai 💖
Xiang Liu (xiang.liu@oracle.com) 💖
Oracle 💖

Specification document(s):

edge-arch [25] 📜

2.1.102. Header field: Surrogate-Control 🌐

Applicable protocol: http [11] 🎀

Status: informational ℹ️

Author/change controller:

Mark Nottingham (mnot@akamai.com) 💖
Akamai 💖
Xiang Liu (xiang.liu@oracle.com) 💖
Oracle 💖

Specification document(s):

edge-arch [25] 📜

2.1.103. Header field: TCN 🦋

Applicable protocol: http [11] 🎀

Status: experimental 🧪

Author/change controller:

Andrew H. Mutz (mutz@hpl.hp.com) 💖
Koen Holtman (koen@win.tue.nl) 💖

Specification document(s):

RFC2295 [7] 📜

2.1.104. Header field: TE ✨

Applicable protocol: http [11] 🎀

Status: standard ✅

Author/change controller:

IETF (iesg@ietf.org) 💜
Internet Engineering Task Force 💜

Specification document(s):

RFC2616 [11] 📜

2.1.105. Header field: Timeout 🌸

Applicable protocol: http [11] 🎀

Status: standard ✅

Author/change controller:

IETF (iesg@ietf.org) 💜
Internet Engineering Task Force 💜

Specification document(s):

RFC2518 [10] 📜

2.1.106. Header field: Trailer 🧚

Applicable protocol: http [11] 🎀

Status: standard ✅

Author/change controller:

IETF (iesg@ietf.org) 💜
Internet Engineering Task Force 💜

Specification document(s):

RFC2616 [11] 📜

2.1.107. Header field: Transfer-Encoding 🚚

Applicable protocol: http [11] 🎀

Status: standard ✅

Author/change controller:

IETF (iesg@ietf.org) 💜
Internet Engineering Task Force 💜

Specification document(s):

RFC2616 [11] 📜

2.1.108. Header field: URI 🍓

Applicable protocol: http [11] 🎀

Status: standard ✅

Author/change controller:

IETF (iesg@ietf.org) 💜
Internet Engineering Task Force 💜

Specification document(s):

RFC2068 [4] 📜

2.1.109. Header field: Upgrade 🚀

Applicable protocol: http [11] 🎀

Status: standard ✅

Author/change controller:

IETF (iesg@ietf.org) 💜
Internet Engineering Task Force 💜

Specification document(s):

RFC2616 [11] 📜

2.1.110. Header field: User-Agent 🌈

Applicable protocol: http [11] 🎀

Status: standard ✅

Author/change controller:

IETF (iesg@ietf.org) 💜
Internet Engineering Task Force 💜

Specification document(s):

RFC2616 [11] 📜

2.1.111. Header field: Variant-Vary ✨

Applicable protocol: http [11]

Status: experimental

Author/change controller:

Andrew H. Mutz (mutz@hpl.hp.com)
Koen Holtman (koen@win.tue.nl)

Specification document(s): RFC2295 [7]

2.1.112. Header field: Vary 💖

Applicable protocol: http [11]

Status: standard

Author/change controller:

IETF (iesg@ietf.org)
Internet Engineering Task Force

Specification document(s): RFC2616 [11]

2.1.113. Header field: Via 🦋

Applicable protocol: http [11]

Status: standard

Author/change controller:

IETF (iesg@ietf.org)
Internet Engineering Task Force

Specification document(s): RFC2616 [11]

2.1.114. Header field: WWW-Authenticate 🔐

Applicable protocol: http [11]

Status: standard

Author/change controller:

IETF (iesg@ietf.org)
Internet Engineering Task Force

Specification document(s): RFC2616 [11]

2.1.115. Header field: Want-Digest 🌸

Applicable protocol: http [11]

Status: standard

Author/change controller:

IETF (iesg@ietf.org)
Internet Engineering Task Force

Specification document(s): RFC3230 [17]

2.1.116. Header field: Warning 🚨

Applicable protocol: http [11]

Status: standard

Author/change controller:

IETF (iesg@ietf.org)
Internet Engineering Task Force

Specification document(s): RFC2616 [11]

2.2. Provisional HTTP Header Field Submissions 🧚

okay so this bit is the provisional list, which is basically the "still in the group chat, not official yet" section 💅 here's the whole roster:

Header name             Protocol
-----------             --------
Compliance                http
Content-Transfer-Encoding http
Cost                      http
Message-ID                http
Non-Compliance            http
Optional                  http
Resolution-Hint           http
Resolver-Location         http
SubOK                     http
Subst                     http
Title                     http
UA-Color                  http
UA-Media                  http
UA-Pixels                 http
UA-Resolution             http
UA-Windowpixels           http
Version                   http

2.2.1. Header field: Compliance 🎀

Applicable protocol: http [11]

Status: provisional

Author/change controller:

Jeffrey C. Mogul (mogul@wrl.dec.com), Western Research Laboratory, Digital Equipment Corporation
Josh Cohen (josh@netscape.com), Netscape Communications Corporation
Scott Lawrence (lawrence@agranat.com), Agranat Systems, Inc.

Specification document(s): OPTIONS messages [31]

2.2.2. Header field: Content-Transfer-Encoding 🌈

Applicable protocol: http [11]

Status: provisional

Author/change controller:

Tim Berners-Lee (timbl@w3.org)
MIT Laboratory for Computer Science

Specification document(s): Object Headers [2]

2.2.3. Header field: Cost 💸

Applicable protocol: http [11]

Status: provisional

Author/change controller:

Tim Berners-Lee (timbl@w3.org)
MIT Laboratory for Computer Science

Specification document(s): Object Headers [2]

2.2.4. Header field: Message-ID 🫶

Applicable protocol: http [11]

Status: provisional

Author/change controller:

Tim Berners-Lee (timbl@w3.org)
MIT Laboratory for Computer Science

Specification document(s): Object Headers [2]

2.2.5. Header field: Non-Compliance 🙈

Applicable protocol: http [11]

Status: provisional

Author/change controller:

Jeffrey C. Mogul (mogul@wrl.dec.com), Western Research Laboratory, Digital Equipment Corporation
Josh Cohen (josh@netscape.com), Netscape Communications Corporation
Scott Lawrence (lawrence@agranat.com), Agranat Systems, Inc.

Specification document(s): OPTIONS messages [31]

2.2.6. Header field: Optional 🍓

Applicable protocol: http [11]

Status: provisional

Author/change controller:

John Mallery (jcma@ai.mit.edu), MIT Artificial Intelligence Laboratory
Lewis Girod (girod@lcs.mit.edu), MIT Laboratory for Computer Science
Benjie Chen (benjie@lcs.mit.edu), MIT Laboratory for Computer Science
Henrik Frystyk Nielsen (frystyk@w3.org), World Wide Web Consortium

Specification document(s): WIRE [32]

2.2.7. Header field: Resolution-Hint 🔍

Applicable protocol: http [11]

Status: provisional

Author/change controller:

John Mallery (jcma@ai.mit.edu), MIT Artificial Intelligence Laboratory
Lewis Girod (girod@lcs.mit.edu), MIT Laboratory for Computer Science
Benjie Chen (benjie@lcs.mit.edu), MIT Laboratory for Computer Science
Henrik Frystyk Nielsen (frystyk@w3.org), World Wide Web Consortium

Specification document(s): WIRE [32]

2.2.8. Header field: Resolver-Location 📍

Applicable protocol: http [11]

Status: provisional

Author/change controller:

John Mallery (jcma@ai.mit.edu), MIT Artificial Intelligence Laboratory
Lewis Girod (girod@lcs.mit.edu), MIT Laboratory for Computer Science
Benjie Chen (benjie@lcs.mit.edu), MIT Laboratory for Computer Science
Henrik Frystyk Nielsen (frystyk@w3.org), World Wide Web Consortium

Specification document(s): WIRE [32]

2.2.9. Header field: SubOK 🌙

Applicable protocol: http [11]

Status: provisional

Author/change controller:

Jeffrey C. Mogul (mogul@wrl.dec.com), Western Research Laboratory, Digital Equipment Corporation
Arthur van Hoff (avh@marimba.com), Marimba, Inc.

Specification document(s): Duplicate Suppression [33]

2.2.10. Header field: Subst 🪄

Applicable protocol: http [11]

Status: provisional

Author/change controller:

Jeffrey C. Mogul (mogul@wrl.dec.com), Western Research Laboratory, Digital Equipment Corporation
Arthur van Hoff (avh@marimba.com), Marimba, Inc.

Specification document(s): Duplicate Suppression [33]

2.2.11. Header field: Title 👑

Applicable protocol: http [11]

Status: provisional

Author/change controller:

Tim Berners-Lee (timbl@w3.org)
MIT Laboratory for Computer Science

Specification document(s): Object Headers [2]

2.2.12. Header field: UA-Color 🎨

Applicable protocol: http [11]

Status: provisional

Author/change controller:

Larry Masinter (LMM@acm.org), Adobe Systems
Lou Montulli (montulli@netscape.com), Netscape Communications Corp.
Andrew H. Mutz (mutz@hpl.hp.com), Hewlett-Packard Company

Specification document(s): UA Attributes [30]

2.2.13. Header field: UA-Media 📺

Applicable protocol: http [11]

Status: provisional

Author/change controller:

Larry Masinter (LMM@acm.org), Adobe Systems
Lou Montulli (montulli@netscape.com), Netscape Communications Corp.
Andrew H. Mutz (mutz@hpl.hp.com), Hewlett-Packard Company

Specification document(s): UA Attributes [30]

2.2.14. Header field: UA-Pixels 🖼️

Applicable protocol: http [11]

Status: provisional

Author/change controller:

Larry Masinter (LMM@acm.org), Adobe Systems
Lou Montulli (montulli@netscape.com), Netscape Communications Corp.
Andrew H. Mutz (mutz@hpl.hp.com), Hewlett-Packard Company

Specification document(s): UA Attributes [31]

2.2.15. Header field: UA-Resolution 🖥️

Applicable protocol: http [11]

Status: provisional

Author/change controller:

Larry Masinter (LMM@acm.org), Adobe Systems
Lou Montulli (montulli@netscape.com), Netscape Communications Corp.
Andrew H. Mutz (mutz@hpl.hp.com), Hewlett-Packard Company

Specification document(s): UA Attributes [30]

2.2.16. Header field: UA-Windowpixels 🪟

Applicable protocol: http [11]

Status: provisional

Author/change controller:

Larry Masinter (LMM@acm.org), Adobe Systems
Lou Montulli (montulli@netscape.com), Netscape Communications Corp.
Andrew H. Mutz (mutz@hpl.hp.com), Hewlett-Packard Company

Specification document(s): UA Attributes [30]

2.2.17. Header field: Version 🔖

Applicable protocol: http [11]

Status: provisional

Author/change controller:

Tim Berners-Lee (timbl@w3.org)
MIT Laboratory for Computer Science

Specification document(s): Object Headers [2]

3. IANA Considerations 📋

This specification provides initial registrations of HTTP header fields in the "Permanent Message Header Field Registry", defined by Registration Procedures for Message Header Fields [1].

It also provides initial submissions of HTTP header fields in the "Provisional Message Header Field Repository", defined by the same document.

4. Security Considerations 🔒

Okay, this one is serious bestie 😤 No security considerations are introduced by this document beyond those already inherent in use of the HTTP header fields referenced. So the risks are the ones that already come with these header fields, nothing new is added here 🛡️

5. Acknowledgements 🫶

The authors would like to thank Graham Klyne for his work in defining the message header registries, his input and help in preparing this document, and the registry generation software. Huge thank-you to Graham! 🌷

6. Informative References ✨

okay so these are the receipts 💅 every source the spec leans on, listed in order:

[1] Klyne, G., Nottingham, M., and J. Mogul, "Registration Procedures for Message Header Fields", BCP 90, RFC 3864, September 2004.
[2] Berners-Lee, T., "Object Header lines in HTTP", May 1994, <http://www.w3.org/Protocols/HTTP/Object_Headers.html>.
[3] Berners-Lee, T., Fielding, R., and H. Nielsen, "Hypertext Transfer Protocol -- HTTP/1.0", RFC 1945, May 1996.
[4] Fielding, R., Gettys, J., Mogul, J., Nielsen, H., and T. Berners-Lee, "Hypertext Transfer Protocol -- HTTP/1.1", RFC 2068, January 1997.
[5] Kristol, D. and L. Montulli, "HTTP State Management Mechanism", RFC 2109, February 1997.
[6] Mogul, J. and P. Leach, "Simple Hit-Metering and Usage-Limiting for HTTP", RFC 2227, October 1997.
[7] Holtman, K. and A. Mutz, "Transparent Content Negotiation in HTTP", RFC 2295, March 1998.
[8] Holtman, K., "The Safe Response Header Field", RFC 2310, April 1998.
[9] Masinter, L., "Hyper Text Coffee Pot Control Protocol (HTCPCP/1.0)", RFC 2324, April 1998.
[10] Goland, Y., Whitehead, E., Faizi, A., Carter, S., and D. Jensen, "HTTP Extensions for Distributed Authoring -- WEBDAV", RFC 2518, February 1999.
[11] 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.
[12] Franks, J., Hallam-Baker, P., Hostetler, J., Lawrence, S., Leach, P., Luotonen, A., and L. Stewart, "HTTP Authentication: Basic and Digest Access Authentication", RFC 2617, June 1999.
[13] Rescorla, E. and A. Schiffman, "The Secure HyperText Transfer Protocol", RFC 2660, August 1999.
[14] Nielsen, H., Leach, P., and S. Lawrence, "An HTTP Extension Framework", RFC 2774, February 2000.
[15] Kristol, D. and L. Montulli, "HTTP State Management Mechanism", RFC 2965, October 2000.
[16] Mogul, J., Krishnamurthy, B., Douglis, F., Feldmann, A., Goland, Y., van Hoff, A., and D. Hellerstein, "Delta encoding in HTTP", RFC 3229, January 2002.
[17] Mogul, J. and A. Van Hoff, "Instance Digests in HTTP", RFC 3230, January 2002.
[18] Clemm, G., Amsden, J., Ellison, T., Kaler, C., and J. Whitehead, "Versioning Extensions to WebDAV (Web Distributed Authoring and Versioning)", RFC 3253, March 2002.
[19] Whitehead, J. and J. Reschke, Ed., "Web Distributed Authoring and Versioning (WebDAV) Ordered Collections Protocol", RFC 3648, December 2003.
[20] Hoff, A., Payne, J., Hapner, M., Carter, S., and M. Medin, "The HTTP Distribution and Replication Protocol", W3C NOTE NOTE-drp-19970825, August 1997.
[21] Raggett, D., Hors, A., and I. Jacobs, "HTML 4.01 Specification", W3C REC REC-html401-19991224, December 1999.
[22] Hensley, P., Metral, M., Shardanand, U., Converse, D., and M. Myers, "Implementation of OPS Over HTTP", W3C NOTE NOTE-OPS-OverHTTP, June 1997.
[23] Marchiori, M., "The Platform for Privacy Preferences 1.0 (P3P1.0) Specification", W3C REC REC-P3P-20020416, April 2002.
[24] Krauskopf, T., Miller, J., Resnick, P., and W. Treese, "PICS 1.1 Label Distribution -- Label Syntax and Communication Protocols", W3C REC REC-PICS-labels-961031, October 1996.
[25] Nottingham, M. and X. Liu, "Edge Architecture Specification", W3C NOTE NOTE-edge-arch-20010804, August 2001.
[26] Chung, E. and D. Dardailler, "White Paper: Joint Electronic Payment Initiative", W3C NOTE NOTE-jepi-970519, May 1997.
[27] Hallam-Baker, P., "Notification for Proxy Caches", W3C NOTE WD-proxy-960221, February 1996.
[28] Box, D., Ehnebuske, D., Kakivaya, G., Layman, A., Mendelsohn, N., Nielsen, H., Thatte, S., and D. Winer, "Simple Object Access Protocol (SOAP) 1.1", W3C NOTE NOTE-SOAP-20000508, May 2000.
[29] Connolly, D., Prod'hommeaux, E., Nielsen, H., and R. Khare, "PEP Specification: an Extension Mechanism for HTTP", Nov 1998, <http://www.w3.org/TR/WD-http-pep>.
[30] Masinter, L., Montulli, L., and A. Mutz, "User-Agent Display Attributes Headers", Work in Progress, November 1996.
[31] Mogul, J., Cohen, J., and S. Lawrence, "Specification of HTTP/1.1 OPTIONS messages", Work in Progress, August 1997.
[32] Girod, L., Chen, B., Henrik, H., and J. Mallery, "WIRE - W3 Identifier Resolution Extensions", Work in Progress, March 1998.
[33] Mogul, J. and A. van Hoff, "Duplicate Suppression in HTTP", Work in Progress, April 1998.

Authors' Addresses 💌

Mark Nottingham

EMail: mnot@pobox.com URI: <http://www.mnot.net/>

Jeffrey C. Mogul HP Labs 1501 Page Mill Road Palo Alto, CA 94304 US

EMail: JeffMogul@acm.org

Full Copyright Statement 🎀

This document is subject to the rights, licenses and restrictions contained in BCP 78, and except as set forth therein, the authors retain all their rights.

This document and the information contained herein are provided on an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM 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.

Intellectual Property 🌸

okay so the IETF is not picking a side on who owns what 🙈 it takes no position on the validity or scope of any Intellectual Property Rights or other rights that might be claimed to pertain to the implementation or use of the technology described in this document, or on whether any license under such rights might or might not be available. it also doesn't claim to have made any independent effort to identify any such rights. info about how rights work for RFC documents lives in BCP 78 and BCP 79.

copies of IPR disclosures made to the IETF Secretariat, plus any assurances of licenses to be made available, or the result of an attempt to get a general license or permission to use such proprietary rights by implementers or users of this specification, can be found in the IETF on-line IPR repository at <http://www.ietf.org/ipr>.

the IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary rights that may cover technology required to implement this standard. send that info to the IETF at ietf-ipr@ietf.org.

Acknowledgement 🫶

Funding for the RFC Editor function is currently provided by the Internet Society. 💜

📦 where this page comes from

ietf: rfc4229 2005-12
💖 girlified by claude-haiku-5-5 on 2026-10-17: a language model's rewrite of the original, under its terms

RFC 4229

HTTP Header Field Registrations 🎀

Status of This Memo ✨

Copyright Notice 🌸

Abstract 🔥

Table of Contents 🌈

1. Introduction 🎀

2. Registration Templates 💅

2.1. Permanent HTTP Header Field Registrations 🌈

2.1.1. Header field: A-IM ✨

2.1.2. Header field: Accept 🌸

2.1.3. Header field: Accept-Additions 🙈

2.1.4. Header field: Accept-Charset 💖

2.1.5. Header field: Accept-Encoding 🦋

2.1.6. Header field: Accept-Features 🧚

2.1.7. Header field: Accept-Language 🌈

2.1.8. Header field: Accept-Ranges ⭐

2.1.9. Header field: Age 🍓

2.1.10. Header field: Allow 👑

2.1.11. Header field: Alternates 🔥

2.1.12. Header field: Authentication-Info 🫶

2.1.13. Header field: Authorization 💜

2.1.14. Header field: C-Ext ✨

2.1.15. Header field: C-Man 🎀

2.1.16. Header field: C-Opt 🦋

2.1.17. Header field: C-PEP 🌸

2.1.18. Header field: C-PEP-Info 🌈

2.1.19. Header field: Cache-Control 💅

2.1.20. Header field: Connection 🫶

2.1.21. Header field: Content-Base 🍓

2.1.22. Header field: Content-Disposition ⭐

2.1.23. Header field: Content-Encoding 💖

2.1.24. Header field: Content-ID 🎀

2.1.25. Header field: Content-Language 🌸

2.1.26. Header field: Content-Length 💖

2.1.27. Header field: Content-Location ✨

2.1.28. Header field: Content-MD5 🔥

2.1.29. Header field: Content-Range 🦋

2.1.30. Header field: Content-Script-Type 🌈

2.1.31. Header field: Content-Style-Type 💜

2.1.32. Header field: Content-Type ⭐

2.1.33. Header field: Content-Version 🧚

2.1.34. Header field: Cookie 🍓

2.1.35. Header field: Cookie2 🦋

2.1.36. Header field: DAV 💖

2.1.37. Header field: Date ✨

2.1.38. Header field: Default-Style 🌸

2.1.39. Header field: Delta-Base 💜

2.1.40. Header field: Depth 🧚

2.1.41. Header field: Derived-From 🌈

2.1.42. Header field: Destination ⭐

2.1.43. Header field: Differential-ID 💅

2.1.44. Header field: Digest 🔥

2.1.45. Header field: ETag 💖

2.1.46. Header field: Expect 🌸

2.1.47. Header field: Expires 🎀

2.1.48. Header field: Ext 🦋

2.1.49. Header field: From 💅

2.1.50. Header field: GetProfile 🌈

2.1.51. Header field: Host ⭐

2.1.52. Header field: IM 🍓

2.1.53. Header field: If 🔥

2.1.54. Header field: If-Match 🧚

2.1.55. Header field: If-Modified-Since 🎀

2.1.56. Header field: If-None-Match 🦋

2.1.57. Header field: If-Range 🌈

2.1.58. Header field: If-Unmodified-Since 💖

2.1.59. Header field: Keep-Alive 🌸

2.1.60. Header field: Label 🧚

2.1.61. Header field: Last-Modified 🔥

2.1.62. Header field: Link 🌈

2.1.63. Header field: Location 💜

2.1.64. Header field: Lock-Token 🍓

2.1.65. Header field: MIME-Version 🎀

2.1.66. Header field: Man 🌸

2.1.67. Header field: Max-Forwards 🦋

2.1.68. Header field: Meter 🌈

2.1.69. Header field: Negotiate ✨

2.1.111. Header field: Variant-Vary ✨

2.1.112. Header field: Vary 💖