Blocks of content available (minimum)
Group: layout • Guideline: structure
Summary in Plain English
The page is divided into meaningful blocks that software can identify, and each block is given enough surrounding space to be seen as a block.
Why It Matters
The programmatic part is what lets a screen reader jump between sections; the spacing is what lets a sighted reader see where one ends and the next begins.
Test Procedure from the W3C Draft
Quoted from the provision's informative document, informative/guidelines/layout/structure/blocks-of-content-available-minimum.md. It is the group's own procedure, not an editorial testing guide.
HTML sufficient space
Procedure
- Identify meaningful blocks of content in the page/view that are not bounded by a visual border.
- Examine the computed style to determine the total of margin, padding and border spacing.
- Check that the spacing between all adjacent meaningful blocks of content is sufficient.
Expected results
- #3 is true.
Programmatically identifiable meaningful blocks of content
Procedure
For each meaningful blocks of content in the page/view:
- Check that an appropriate role is being used for the meaningful blocks of content in the source code.
- Check using assistive technology that an appropriate role is being used for the meaningful blocks of content.
Expected results
- #1 or #2 is true.
W3C Working Group Status
The draft records no open editors' notes on this provision.
W3C Threads on This Provision
2 GitHub threads carrying 9 comments, fetched from w3c/wcag3 by the tracker. Titles, numbers and states are the threads' own.
What the Argument Is About
Whether a block of content being visually indistinct is an accessibility failure at all, and whether "sufficient surrounding space" can be written as a requirement anyone can test.
Positions taken in the thread
Responding to the opening questions in #19, asks whether there is a requirement for headings to be visually distinct in the first place, since content that is indistinct for every reader alike looks like a design quality issue rather than an accessibility one. On the font versus typeface point he replies that it is fine as long as things are programmatically different. He also questions the "sufficient semantics" framing, reading it as sufficient meaning and suggesting, with the hedge "(I don’t think)", that WCAG cannot require authors who write meaningless headings to rewrite them, while asking whether something different was meant.
Argues visual hierarchy is squarely an accessibility issue for COGA among others, and that it is also a contrast issue: the amount of padding around a text block, line spacing and letter spacing all change perceived contrast, and this is most critical for blocks of body text. Contends the primary driver of perceived contrast is spatial, chiefly rasterized font weight, because weight sets the spatial frequency the contrast sensitivity function responds to. Cites Lovie-Kitchin and colleagues for contrast reserve figures keyed to use case, roughly 20 times the JND threshold for article body text down to 3 times for non-fluent spot reading.
Wants the methods currently used to separate blocks and headings surveyed first, so a new requirement does not accidentally outlaw one that works, and notes that distinctions are frequently used in combination rather than singly. Lists boldness, font size, typeface, indentation, underlines and overlines, italicization, small caps, script, color, textual or iconographic markers and text alignment. Refines Myndex's three-way split into four groups: spatial, visual text attributes, content and external indicators.
Opened #476 asking for a re-evaluation of whether the visual and programmatic aspects of meaningful content blocks should be separate requirements, because one can be satisfied while the other is not. Also asks for "sufficient surrounding space" to be defined, and for exceptions to be considered where a particular layout choice means spacing may not be required.
Points from GreggVan that giacomo-petri listed in #476 for review, without adding his own view on them: the draft requires information to be programmatically determinable that is not visually determinable, which reverses the usual direction, and the wording needs to say that where content appears as a block carrying semantic meaning, that block also has to be programmatically determinable. On spacing, paragraphs often have no more space between them than between the lines inside them, yet they are meaningful blocks, so the reductio is whether every document must now add space between every paragraph, and whether the answer is one pixel, two, or three.
Agreed
- Color alone should not be the distinguishing factor. u9000-Nine is content not to count color as a distinction despite it being common practice and the Word default; Myndex clarifies color is genuinely useful but must accompany weight, size and family rather than carry the distinction on its own, since perception of color varies enormously even among standard vision and shifts with context.
- Relative size is a legitimate distinction, absolute size is not. u9000-Nine proposed that a heading being larger than the body text, whatever size that is, should count; Myndex agreed font size is and should be a distinguishing feature.
- Font weight belongs with the spatial and contrast group rather than with font styling, because weight determines spatial frequency and therefore perceived contrast. u9000-Nine accepted the reclassification.
Still open
- Whether visual distinctness of blocks is in scope at all. GreggVan asked in September 2023; Myndex later asserted that visual hierarchy is an accessibility issue (COGA among others) without replying to him directly, and the question was not settled.
- What "sufficient surrounding space" means and whether a number can be attached to it. giacomo-petri raised this as one of the items in #476; the paragraph-spacing reductio quoted there is unanswered.
- Whether visual and programmatic block structure should be one requirement or two (giacomo-petri, #476), and what exceptions exist where a layout choice makes spacing unnecessary.
- Where text decoration sits. u9000-Nine asked why it appears under both layout and non-text; Myndex left it open, leaning non-text when it indicates function such as an underlined link and layout when it is merely divisional.
- Whether container behaviour under large text zoom belongs to this provision. Myndex wants the smallest body text scalable to roughly 80 to 92 px, an x-height near 42 px and a zoom of 450 to 500 percent, with already-larger text scaling by a smaller percentage, and notes 500 percent is untenable on a phone so device media queries are needed.
Note
The nine comments here all come from #19, which is labelled for this provision and for Heading structure available, so the taxonomy work is shared between the two. Substantively it is a two-person exchange between Myndex and u9000-Nine over about two and a half weeks in November and December 2023 that converged on a classification but never produced proposed requirement text; WilcoFiers's opening questions and GreggVan's scope challenge were never resolved, and #476 reopens the same ambiguities two years later with no replies yet.
WCAG 2.2 Criteria That Map Here
From this site's reviewed WCAG 2.2 → WCAG 3 map. The map is an interpretation, not a W3C mapping: W3C has not published one yet.
W3C Raw Source Text
Verbatim from guidelines/groups/layout/structure/blocks-of-content-available-minimum.md · informative document: informative/guidelines/layout/structure/blocks-of-content-available-minimum.md
Meaningful blocks of content are programmatically determinable and visually presented with sufficient surrounding space.