[css-2025][css-pseudo-4] Add typographic pseudo-elements to Safe to Release exceptions

[SebastianZ]

Splitting the discussion from #10687 for adding typographic pseudo-elements from CSS Pseudo-Elements 4 (basically all from CSS 2 with double-colon syntax plus ::prefix and ::postfix) to the Safe to Release pre-CR Exceptions section of the CSS Snapshot 2025.

Data to consider:

• Spec. status: WD (last published: 27 June 2025)
• Implemented in all major browsers for many years
• WPT: passing tests: Chrome: 3, Edge: 3, Firefox: 3, Safari: 3; interop: 3 / 3 (100.0%)
• Open issues: on GitHub: ~14, in spec.: 0

Summary: Very high interoperability, only minimal number of WPTs, many open issues

Sebastian

[css-meeting-bot]

The CSS Working Group just discussed [css-2025][css-pseudo-4] Add typographic pseudo-elements to Safe to Release exceptions.

The full IRC log of that discussion

<florian> SebastianZ: fantasai mentioned in another issue that we need to resolve on a syntax question
<florian> SebastianZ: the :: syntax has been in all browsers for many years
<florian> ChrisL: css2 had the same thing, but with a single colon
<florian> SebastianZ: so we should resolve that all the typographic pseudo elements, with the :: syntax, are safe to release
<dbaron> https://www.w3.org/TR/selectors-3/#pseudo-elements
<florian> dbaron: are these not in the selectors 3 recommendation
<florian> dbaron: which pseudos?
<florian> dbaron: ::first-line, ::first-letter, ::before, ::after are in selectors-3, ::marker is not
<florian> ChrisL: nor are ::prefix and ::postfix
<florian> SebastianZ: but I think these last two were in css2
<florian> dbaron: no
<florian> astearns: of the typographic pseudos, we're only concerned about ::prefix and ::postfix
<florian> astearns: ::marker is in a different category, tree abiding pseudos
<florian> SebastianZ: the idea was to mark all that were part of css2 as safe to release with the :: colon syntax
<florian> astearns: if they're in selectors 3, we don't need to
<florian> dbaron: the only missing one are ::prefix and ::postfix
<florian> SebastianZ: I don't remember why I added those, probably tested them before
<florian> astearns: we don't seem to have test for those, and edits seem to be pending too

[SebastianZ]

As it was pointed out in the call, ::first-line, ::first-letter, ::before, and ::after are already in Selectors 3, which is already part of the official definition.
And ::prefix and ::suffix are actually implemented nowhere yet, it seems.

Therefore, I'm closing this.

Sebastian