WCAG 3.0 is an active W3C Working Draft in development by the AGWG. Requirements, assertions, the conformance model and reporting tiers are still being developed and may change. The latest published draft is the 10 September 2026 Working Draft; this site follows the editors’ draft, which also includes exploratory provisions.
Sentences avoid nested clauses. Poetic, scriptural, artistic and expressive content is exempt, as is legal information.
Why It Matters
Each nested clause is something the reader has to hold in mind while the sentence finishes. That load is what makes otherwise simple information unreadable for people with cognitive disabilities.
For each sentence:
For all nested clauses in the sentence (introduced by nesting conjunctions such as ‘because’, ‘although’, ‘if’, ‘that’, ‘which’, ‘who’, ‘when’, and ‘where’).
Check that each initial nested clause does not contain other nested clauses within it.
Check that a technology in the accessibility support set meets ‘No nested clauses’.
Expected results
#1 or #2 is true.
W3C Working Group Status
W3C Maturity Status:developing
Track / Group:text-and-wording
The draft records no open editors' notes on this provision.
W3C Threads on This Provision
5 GitHub threads carrying 2 comments,
fetched from w3c/wcag3 by the
tracker. Titles, numbers and states are the threads' own.
What the Argument Is About
Five mostly single-comment issues circling one question — whether a rule about clause nesting is feasible, useful and valid outside English — with only chaals and murata2makoto offering substantive argument and neither answered.
Positions taken in the thread
Too hard for authors without writing resourcessydneycolemanfromgoogle, julierawe
julierawe opened #552 carrying a January 2026 survey comment from sydneycolemanfromgoogle that the requirement will be incredibly challenging for parties without dedicated writing support and does not seem to add significantly to understanding. julierawe's answer is procedural and tooling-based: the requirement was moved from core to supplemental after the survey closed, which may resolve part of the concern, and free AI tools already flag complex sentence structures, so WCAG 3 could encourage them to call out nested clauses specifically.
Not too hard, but too simplisticchaals
Concedes the requirement takes real work and is very hard without someone who works on language, but notes few sites have nobody working on content, so difficulty is not the objection. Accepts that removing nested clauses generally does improve understanding, much more so for deep nesting. His actual complaint is that the requirement is too simple to be very useful: clear writing is hard to test because people disagree on what is clear, and rules differ between languages so a test built for one is often useless in another. A paragraph in his comment about the requirement not differentiating by depth of nesting is struck through.
The premise is English-specificmurata2makoto
Argues in #569 that clause nesting is not inherently a readability problem. The English centre-embedded example about the rat, the cat and the dog is genuinely hard to process, but the equivalent Japanese structure is unremarkable for native speakers, and the same holds for Korean and other head-final languages. Concludes that the real source of difficulty varies by language — word order ambiguity, unclear referents — and that treating nested clauses as a general problem overgeneralises from English.
Editorial fixes to the examplessydneycolemanfromgoogle, hidde
In #529 sydneycolemanfromgoogle asked whether "aced" should be replaced in a pass example as an idiom that may be hard to translate; hidde changed it to "did well on" in commit b1351ad and closed the issue on merge. In the still-open #530 sydneycolemanfromgoogle notes the listed nesting conjunctions may read as exhaustive when words like "that" also qualify, and supplies a rewritten test procedure making the list open-ended.
Agreed
"Aced" was an inappropriate example word and has been replaced in the draft — the only thing actually resolved across these five issues.
Removing nested clauses generally does aid comprehension in English, which chaals grants even while objecting to the requirement's form.
Still open
Whether moving the requirement from core to supplemental addresses sydneycolemanfromgoogle's feasibility objection — julierawe proposed reaching out to ask and no outcome is recorded.
Whether it should move further, from supplemental to best practice, raised at the February 3rd AG meeting and tracked in #560 with no comments since.
Whether the requirement is valid for head-final languages at all (murata2makoto), unanswered since February 2026.
sydneycolemanfromgoogle's proposed non-exhaustive rewording of the conjunction list in #530.
Note
#560 summarises an AG meeting rather than hosting discussion: it records unnamed members raising feasibility concerns with specialized content, and another member citing complex sentence structures as a significant cognitive barrier in their own experience. Four of the five issues have zero or one comment.
Sentences do not include nested clauses.
:::except-when
- text content:
* is poetic, scriptural, artistic, or expressive rather than informational, or
* provides legal information.
:::
:::example
The sentence:
> "The teacher was surprised that the student who did well on yesterday's test was absent today."
Includes the nested clause "who did well on yesterday's test" of the clause "was surprised that the student ... was absent today".
This could be written without the nested clause as:
> "The teacher was surprised that the student was absent today. This was unexpected because he did well on yesterday's test."
:::