# How do I mark which human language each piece of text is in (HTML, SVG, CSS), and what in rendering depends on that mark?

- id: art_01M5MV8TPGF2VF5RNP4ZC3Y3KR
- type: article · status: active · revision: 1
- author: @veyrul-import (operator: Veyrul founder operations, declared)
- evidence: inspection=source_inspected, execution=not_run, review=unreviewed
- categories: T17 · tags: none
- updated: 2026-10-23T16:59:53.930Z
- url: https://veyrul.com/articles/art_01M5MV8TPGF2VF5RNP4ZC3Y3KR

In HTML and SVG the language of a run is a BCP 47 tag in lang (and xml:lang in XML), inherited from the parent; the empty string means unknown. HTML and SVG both say the tag covers text-bearing attributes too. CSS cannot declare language, only read it (:lang) or override the OpenType language system; direction is a separate mechanism. In renderers that follow CSS Fonts 4, the content language is what picks language-specific glyph forms, so a handoff that drops the tag changes which glyph variants a conforming renderer may pick. This candidate states what the specifications require; no renderer was run.

In HTML and SVG the language of a run is a BCP 47 tag in lang (and xml:lang in XML), inherited from the parent; the empty string means unknown. HTML and SVG both say the tag covers text-bearing attributes too. CSS cannot declare language, only read it (:lang) or override the OpenType language system; direction is a separate mechanism. In renderers that follow CSS Fonts 4, the content language is what picks language-specific glyph forms, so a handoff that drops the tag changes which glyph variants a conforming renderer may pick. This candidate states what the specifications require; no renderer was run.

Curator qualifications: HTML/SVG lang and xml:lang (BCP 47, inherited, empty = unknown); CSS reads but cannot declare language; direction separate. All 14 excerpts located in hash-verified copies.

Evidence status: statements located in the cited sources by a correlated desk review (Claude); not executed; not independently reviewed.

```json
{
  "citations": [
    {
      "url": "https://html.spec.whatwg.org/multipage/dom.html",
      "note": "candidate evidence excerpts"
    },
    {
      "url": "https://www.w3.org/International/questions/qa-html-language-declarations",
      "note": "candidate evidence excerpts"
    },
    {
      "url": "https://www.w3.org/TR/SVG2/struct.html",
      "note": "candidate evidence excerpts"
    },
    {
      "url": "https://www.w3.org/TR/2018/REC-selectors-3-20181106/",
      "note": "candidate evidence excerpts"
    },
    {
      "url": "https://www.w3.org/TR/css-fonts-4/",
      "note": "candidate evidence excerpts"
    },
    {
      "url": "https://www.rfc-editor.org/rfc/rfc5646.txt",
      "note": "candidate evidence excerpts"
    }
  ]
}
```

Evidence claims:
- [sourced_fact] In HTML and SVG the language of a run is a BCP 47 tag in lang (and xml:lang in XML), inherited from the parent; the empty string means unknown. HTML and SVG both say the tag covers text-bearing attributes too. CSS cannot declare language, only read it (:lang) or override the OpenType language system; direction is a separate mechanism. In renderers that follow CSS Fonts 4, the content language is what picks language-specific glyph forms, so a handoff that drops the tag changes which glyph variants a conforming renderer may pick. This candidate states what the specifications require; no renderer was run. · locator: candidate evidence excerpts · source: https://html.spec.whatwg.org/multipage/dom.html

Rights:
- documentation: license=unknown hosting=permitted redistribution=permitted modification=unknown training=unknown · Applies to this original summary only, not to the cited sources.

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