[media-types] Review request for updated registration of text/css

[Chris Lilley <[e-mail]>]

Hello,

In accordance with RFC6838 section 5.5 Change Procedure, this is a 
request to update the text/css Internet Media Type.

CSS stylesheets have used text/css  since 1995, and it was registered by 
RFC2318 in March 1998. It is in widespread use.

There are several reasons to update the registration:

1. RFC2318 references the CSS Level 1 specification [1], which dates to 
1996. CSS 2 was released in 1998 [2]. CSS has become a modular 
specification, comprising over 100 modules; the collected state of CSS 
is now published annually, with the most recent publication being this 
year [3]. The canonical definition of CSS [4] is also updated annually 
to point to the latest specification. Therefore, the registration should 
point to the definition in current use, not one from thirty years ago.

2. The definition of the charset parameter in RFC2318 does not follow 
current practice, and is also incompatible with RFC6657. CSS does have 
charset information inside the corresponding payload, but this is 
optional and not widely used. The CSS Syntax level 3 specification [5] 
describes how to determine the encoding in the absence of both a charset 
parameter and an internal label, and this is the method used in practice 
by web browsers. UTF-8 is recommended for new CSS content.

3. RFC6838 states that handling of fragment identifiers (if any) should 
be described, else "N/A" should be added to indicate that there are 
none. RFC2318 is silent on this.

Therefore, starting from CSS 2026, an appendix [6] gives the 
registration template for text/css, addressing all these points. It is 
also included inline in this message. Feedback on this registration 
template is requested and, once all feedback is addressed, W3C wishes to 
update the official text/css registration and obsolete RFC2318

Note: RFC2318 has an empty "Author/Change controller:" section (!) but 
the authors are H.Lie, B. Bos and myself; I am also the W3C staff 
contact for the CSS Working Group, which defines CSS. The updated 
registration gives the CSS Working Group as  author and W3C as change 
controller. Thus in terms of RFC6838 section 5.5 I "pass responsibility" 
as owner to W3C and the W3C CSS Working Group.

[1] https://www.w3.org/TR/CSS1/
[2] https://www.w3.org/TR/1998/REC-CSS2-19980512/
[3] https://www.w3.org/TR/css-2026/
[4] https://www.w3.org/TR/css
[5] https://www.w3.org/TR/css-syntax-3/
[6] https://www.w3.org/TR/css-2026/#media-type

Type name: text

Subtype name: css

Required parameters: none

Optional parameters: charset (but see below)

Encoding considerations:

   For use with transports that are not 8-bit clean, quoted-
   printable encoding is recommended since the majority of
   characters will be CSS syntax and thus correspond to the
   US-ASCII-compatible subrange of UTF-8.

Security considerations:

   CSS is a modular specification and thus, the individual
   Security Considerations section of each CSS module in use
   should be consulted.

Interoperability considerations:

   CSS has proven to be widely interoperable across computer
   platforms, across Web browsers of different makes, and for import
   and export in multiple authoring tools.

Published specification:

   https://www.w3.org/TR/css

Applications that use this media type:

   CSS is device-, platform- and vendor-neutral and is supported by
   a wide range of Web user agents and authoring tools for
   formatting HTML documents.

Fragment identifier considerations:

   N/A

Additional information:

   Deprecated alias names for this type: N/A
   Magic number(s): N/A
   File extension(s): .css

Person & email address to contact for further information:

   The W3C CSS Working Group<[e-mail]>

Intended usage:

   COMMON

Restrictions on usage:

   N/A

Author: The W3C CSS Working Group

Change controller: W3C

Fallback encoding:

   For Web compatibility, to determine the character encoding,
   user agents follow the CSS Syntax Level 3 specification,
   "To determine the fallback encoding of a stylesheet"
   https://www.w3.org/TR/css-syntax-3/#determine-the-fallback-encoding

   Stylesheet authors should author their stylesheets in UTF-8, and
   ensure that either an HTTP header (or equivalent method) declares
   the encoding of the stylesheet to be UTF-8, or that the referring
   document declares its encoding to be UTF-8.


-- 
Chris Lilley
@[e-mail]
W3C Distinguished Expert, Color, Graphics & Fonts
W3C Technical Programming Team, Core Web Design