[selectors] `:lang` for documents without content language and for elements of unknown language; consider `:lang("")` over `:not(:lang("*"))` #6915

myfonj · 2021-12-28T01:19:01Z

Brief questions to answer

Is :lang("*") really valid selector? (Safari supports it and Chrome accepted Issue 1281157 to implement it.)
How to address document that failed to define it's content language?
Should be HTML or equivalent matched by CSS :lang("") or even :lang()? (Not yet proposed nor implemented.)
Is erroneous "undefined" document language equivalent of or is it something different?

Trivia

It seems that there have never been a way for lang() functional pseudo-class to precisely target document without defined content language nor element sub-tree set as such with lang="" attribute.
Selectors-4 draft introduces wildcard support (md) in string argument for matching "any" language of given script or region group (like "*-Latn" or "*-ch"), opening possibility (loophole?) for matching any specified language value using :lang("*") and with conjunction with negation pseudo-class opens possibility to use :not(:lang("*")) for targeting elements that belong to "no specified language" from previous point. While plain "*" value is not explicitly mentioned in the draft, this reportedly already works in current Safari.
Undetermined language occur on any HTML document that does not have explicit lang attribute and does not come with content-language HTTP header or it's "deprecated nasty" counterpart.
For marking ~~non-linguistic~~ unknown language content it is advised to use lang="" attribute. While it is possible to target it with attribute selector ([lang=""]), is does not seem like a right tool and introduces nesting / inheritance problems that lang() selector was created for.

Pseudo-code samples / introductory use cases

Sample 1: Document without content language

HTTP/2 200 OK
[no `content-language: xy,zz` HTTP header here]


	
		[no `` here]
	
	
		[I want target this document.]

Sample 2: element with unknown language content

<html lang="xy">
<body>
 <p>xyx:
  <samp lang="">
   000<em>111<var lang="xy">xvar>em>000
  samp>
 p>
 [I want to target elements with digits and omit elements with letters.]
body>
html>

Problems

Inability to "legally" target specifically undetermined language document or element seems to be quite minor issue, since most CSS approaches tend to start with "common" defaults and progress to language specific with selector of higher specificity. Like

Sample 3: using specificity or order for refining defaults

/* pseudo example of common approach for setting language related styles */
/* hand-waving default */ :root { quotes: '"' '"' "'" "'"; } 
/* specific known language */ :lang(x-whatever) { quotes "→" "←" "☛" "☚"; }

However this approach fails short if CSS' author needs to specifically address poorly marked-up document lacking any content language hint

Sample 4: using `body:not(:lang("*"))` for styling "bad" document

/* Pseudo example "let's put a country flag representing language of the document on it's beginning" */
/* known languages */
body:lang(en-gb)::before { content: url(./flags-gb.svg) / "British English document: "; }
body:lang(en-us)::before { content: url(./flags-us.svg) / "American English document: "; }
/* [etc] */

/* default for "unknown" */
body::before { content: url(./flags-specified-but-unknown.svg) / "Content language of this document is specified but not included in style sheets - please contact style maintainer. "; font-size: small; color: GrayText; }

/* "error message" for "unspecified". topic of this issue */
body:not(:lang("*"))::before { content: url(./flags-unspecified-error.svg) / "This document appears to have no content language specified. If you are it's maintainer fix it ASAP, please. "; }`
body:not(:lang("*")) { background-color: var(--bg-error, Canvas); color: var(--fg-error, GrayText); font-family: cursive; }

(Think Sample 3 above. Also notice that samples use CSS features not yet widely implemented - pseudo element alternative texts and system colors - but those are not related for the issue in question.)

Links, resources and notes

my initial SO question - thanks onkar ruikar for answer, analysis, discussion, workaround and chromium bugreport
tweet
https://www.w3.org/International/questions/qa-css-lang
https://www.w3.org/International/questions/qa-no-language
- "unknown": lang="" / xml:lang="und"
- "known but non-linguistic": lang="zxx";
https://www.w3.org/International/articles/language-tags/
rfc2070: Internationalization of the Hypertext Markup Language

The text was updated successfully, but these errors were encountered:

frivoal · 2022-09-14T16:33:58Z

This was discussed at TPAC by the i18n-WG, and the conclusion was that we should have:

:lang("") that matches lang="" (and descendants…)
:lang("*") that matches everything but lang="" and descendants
a note about lang="und" and lang="" being treated distinctly, despite having similar semantics

css-meeting-bot · 2022-10-12T16:16:12Z

The CSS Working Group just discussed :lang() without document language.

The full IRC log of that discussion

Topic: :lang() without document language
fantasai: When a lang is unknown, there's two ways ot make it unknown
fantasai: first is blank `lang` value
fantasai: second is `lang=und`
fantasai: So how do you match these elements?
fantasai: Proposal is `:lang("")` matches untagged (blank tag), and add a note that `"und"` and `""` are matched differently despite similar semantics
fantasai: And then `:lang("*")` will match any tagged element, including `lang=und` (but won't match untagged/empty string)
TabAtkins: Sorry, hadn't read the discussion, but what's the justification for treating empty string differently from und?
Rossen: I'm not sure about treating them differently
which spec does "und" value come from?
Probably BCP47
Rossen_: Is it in selectors, or text...?
fantasai: und is in the lang tag spec
PaulG: rfc 5646 doesn't have it, it's not in the IDN reg
Rossen_: Perhaps we should delay a week for florian to be able to weigh in
und looks like it's for undetermined

dbaron · 2022-10-12T16:23:34Z

und is discussed in RFC 5646

css-meeting-bot · 2022-10-12T16:33:43Z

The CSS Working Group just discussed :lang() again, and agreed to the following:

RESOLVED: `lang=und` matches :lang("*")`, `lang=""` doesn't match any `:lang()`

The full IRC log of that discussion

Topic: :lang() again
github: https://github.com//issues/6915#issuecomment-1247024928
Rossen_: So question was incosnistency between empty string and und both being "undefined", but they match differently
dbaron dropped a link to the "und" definition in https://www.rfc-editor.org/rfc/rfc5646.html#page-56
florian: Empty string is defined to mean "undefined" by HTML. "und" is defined as "undefined by ISO [something]
florian: Possibly HTML shoudln't have introduced another value to mean the same thing
florian: but it did
florian: i18n group was somewhat struggling with whether to unify it or not
florian: Could b epushed back, but logic was that HTML didn't unify them, and when we do the string matching of lang selectors we do string matching without worrying about the semantics
florian: So our :lang() just does standard lang string parsing + matching
florian: So logic was probably "just keep it simple"
florian: In practice HTML semantics somewhat combine both "explicitly undetermined" and "author couldn't be bothered to specify".
florian: but generally, this is a space where we dont' control the semantics
florian: But I don't think i18n was firm on the conclusion, so if we want to push back it could b eheard
TabAtkins: That does answer the question
TabAtkins: I think I'd be happier if we push back
TabAtkins: but having this distinction from HTML be reflected in our Selectors should be avoided if possible
florian: I think what happened in practice is th eobservation is that "und" wasn't really used on the web, so empty string is how it was actually done in HTML
florian: So effectively we can ignore the "und" value and have :lang("*") match everything *but* the empty string.
florian: And so while technicaly "und" matches the lang, in practice udnefined langs don't match it
fantasai: Yeah, "*" matches "und", but we've had a request for "can I match things without a language", and we'd be able lto do that if we make a distinction in this manner
jfkthame: I think this is a distinctino we should maintain, seems there is a semantic difference between lang being undefined/untagged and explicitly tagged as undetermined
q+
My position is very weak, I defer to whoever has expertise
q-
jfkthame: I agree "und" is rarely used but it does seem semantically meaningful
ack fantasai
fantasai, you wanted to point out * semantics
q+
TabAtkins: If we accept to keep distinct, we don't need to push back. Since several ppl think it's good to keep separate, I'm ok with that
florian: The group that came up with the original rec was just weakly leaning - I think they got it right, but still
ack PaulG
PaulG: AGree with keeping them separate. I suspect coalescing would encourage more "und", where default lang choice is used when undefined, but I think it shouldn't when it's explicitly "undetermined"
Sounds good to me
(I appreciate the "undefined" vs "undetermined" distinction. Was just objecting to two separate "undefined" notions.)
Rossen_: Objections?
RESOLVED: `lang=und` matches :lang("*")`, `lang=""` doesn't match any `:lang()`
scribenick: fantasai

…c#6915

fantasai · 2022-11-08T01:32:03Z

Fixed in 9b51686

aphillips · 2022-11-18T16:40:54Z

@fantasai @frivoal Thanks for this fix. Alas, I just now posted some comments related to the change. I can file a new issue if needed.

@frivoal I'm closing your action for I18N...

…c#6915

myfonj · 2025-05-05T07:34:10Z

Should we reopen this issue? Main changes made in

Fixed in 9b51686

were overwritten by late merge of #4212, so the explicit distinction of lang("*") vs lang("") is quite gone now.

…lly removed by #4212. Fixes #6915.

tabatkins · 2025-05-06T21:45:08Z

Ah, thanks for the pointer. I went ahead and restored that text, it was definitely an accidental removal.

fantasai added selectors-4 Current Work i18n-tracker Group bringing to attention of Internationalization, or tracked by i18n but not needing response. labels Dec 31, 2021

w3cbot mentioned this issue Jan 1, 2022

[selectors] :lang for documents without content language and for elements of unknown language; consider :lang("") over :not(:lang("*")) w3c/i18n-activity#1451

Closed

fantasai added the Agenda+ TPAC label Sep 12, 2022

myfonj mentioned this issue Sep 15, 2022

lang value of document of undetermined language whatwg/html#8288

Closed

css-meeting-bot removed the Agenda+ TPAC label Oct 12, 2022

mozilla-apprentice mentioned this issue Oct 12, 2022

[selectors] :lang for documents without content language and for elements of unknown language; consider :lang("") over :not(:lang("*")) mozilla/wg-decisions#927

Open

frivoal added Closed Accepted by CSSWG Resolution Needs Edits labels Oct 12, 2022

fantasai added a commit to fantasai/csswg-drafts that referenced this issue Nov 3, 2022

[selectors-4] Make empty language strings match untagged elements. w3…

ee492a3

…c#6915

fantasai added Needs Feedback/Review Needs Review of Proposed Text and removed Needs Edits labels Nov 3, 2022

fantasai added a commit to fantasai/csswg-drafts that referenced this issue Nov 7, 2022

[selectors-4] Make empty language strings match untagged elements. w3…

c55ef6b

…c#6915

fantasai added a commit that referenced this issue Nov 7, 2022

[selectors-4] Make empty language strings match untagged elements. #6915

9b51686

fantasai removed Needs Feedback/Review Needs Review of Proposed Text labels Nov 8, 2022

fantasai closed this as completed Nov 8, 2022

jakearchibald pushed a commit to jakearchibald/csswg-drafts that referenced this issue Jan 16, 2023

[selectors-4] Make empty language strings match untagged elements. w3…

8625d75

…c#6915

myfonj mentioned this issue Apr 16, 2025

[selectors-4] Make empty language strings match untagged elements. #6915 #8011

Merged

tabatkins added a commit that referenced this issue May 6, 2025

[selectors-4] Restore text about :lang(*) matching that was accidenta…

5af5799

…lly removed by #4212. Fixes #6915.

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[selectors] `:lang` for documents without content language and for elements of unknown language; consider `:lang("")` over `:not(:lang("*"))` #6915

[selectors] `:lang` for documents without content language and for elements of unknown language; consider `:lang("")` over `:not(:lang("*"))` #6915

myfonj commented Dec 28, 2021 •

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frivoal commented Sep 14, 2022

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fantasai commented Nov 8, 2022

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aphillips commented Nov 18, 2022

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myfonj commented May 5, 2025

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tabatkins commented May 6, 2025

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[selectors] :lang for documents without content language and for elements of unknown language; consider :lang("") over :not(:lang("*")) #6915

[selectors] :lang for documents without content language and for elements of unknown language; consider :lang("") over :not(:lang("*")) #6915

Comments

myfonj commented Dec 28, 2021 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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Brief questions to answer

Trivia

Pseudo-code samples / introductory use cases

Sample 1: Document without content language

Sample 2: element with unknown language content

Problems

Sample 3: using specificity or order for refining defaults

Sample 4: using body:not(:lang("*")) for styling "bad" document

Links, resources and notes

frivoal commented Sep 14, 2022

Uh oh!

css-meeting-bot commented Oct 12, 2022

Uh oh!

dbaron commented Oct 12, 2022

Uh oh!

css-meeting-bot commented Oct 12, 2022

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fantasai commented Nov 8, 2022

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aphillips commented Nov 18, 2022

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myfonj commented May 5, 2025

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tabatkins commented May 6, 2025

Uh oh!

[selectors] `:lang` for documents without content language and for elements of unknown language; consider `:lang("")` over `:not(:lang("*"))` #6915

[selectors] `:lang` for documents without content language and for elements of unknown language; consider `:lang("")` over `:not(:lang("*"))` #6915

myfonj commented Dec 28, 2021 •

edited

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Sample 4: using `body:not(:lang("*"))` for styling "bad" document