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

On 2026-02-27 15:40, Paul Libbrecht wrote:
>
> Was it already decided that a piece of CSS makes no sense within a 
> clipboard?
>
No, but there seems to be no standardized way of doing so.
>
> 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.
>
Looking at the Apple developer documentation "Uniform Type Identifier 
Concepts" [1] it seems that there are a few, Apple-controlled, UTIs in 
the "public" domain and that all others are application-specific and at 
the whim of the developer. There is no registry of defined types, that I 
can see. So while it would be reasonable for a developer to choose, say, 
"org.w3.css" someone else might choose something different.
>
> 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.
>
The Windows "Standard Clipboard Formats" [2] do not have anything 
specific to CSS. They have some generic text types, including "CF_TEXT" 
for "ANSI text" and "CF_UNICODETEXT" for "Unicode text" (presumably 
UTF-16, but it does not say.

So my conclusion is considering clipboard formats was a useful 
suggestion, and I note that the draft registration template in 
draft-ietf-mediaman-6838bis-08 includes both these fields  [3]. But in 
this particular case there is nothing to say for those fields and so 
"N/A" seems appropriate.

The updated registration is included below.

[1] 
https://developer.apple.com/library/archive/documentation/FileManagement/Conceptual/understanding_utis/understand_utis_conc/understand_utis_conc.html
[2] 
https://learn.microsoft.com/en-us/windows/win32/dataxchg/standard-clipboard-formats
[3] 
https://www.ietf.org/archive/id/draft-ietf-mediaman-6838bis-08.html#name-media-type-registration-pro


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
   macOS Uniform Type Identifier(s): N/A
   Windows clipboard name(s): N/A

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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