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

Hello Chris and all,

Was it already decided that a piece of CSS makes no sense within a 
clipboard?

I sort of assume so but I wanted to be sure. I know Apple has a style 
clipboard (a function to copy style so that you can transport it from 
one place to another) and [a UTI type for 
CSS](https://developer.apple.com/documentation/uniformtypeidentifiers/uttype-swift.struct/css) 
so maybe this is relevant? I have, personally, never seen a “copy 
style” function outside of macOS.

Thus I would suggest that a Windows Clipboard Flavour Name (on Windows 
if this can be found there) and the Uniform Type Identifier (on macOS 
and iOS) as above be included within the additional-information section.

Thanks in advance.

Paul



On 27 Feb 2026, at 17:21, Chris Lilley wrote:

> 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<[email protected]>
>
> 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
> @[email protected]
> W3C Distinguished Expert, Color, Graphics & Fonts
> W3C Technical Programming Team, Core Web Design

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