Images Detectable
Group: images-and-media • Guideline: image-alternatives
Summary in Plain English
Where a page contains non-decorative images, those images can be detected - a user can tell that an image is there.
Why It Matters
Knowing an image exists is what lets someone decide to seek out its description. An undetectable image is invisible even to a user who would want it.
Scope: When This Applies
The draft's own conditions, quoted from guidelines/groups/images-and-media/image-alternatives/images-detectable.md.
Applies when
- content includes non-decorative images.
Test Procedure from the W3C Draft
Quoted from the provision's informative document, informative/guidelines/images-and-media/image-alternatives/images-detectable.md. It is the group's own procedure, not an editorial testing guide.
Procedure
For each non-decorative image:
- Check the code to see if it has been marked up in a way that makes it detectable; or
- For technologies where the code cannot be checked, use a screen reader to test that the image is detectable.
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
6 GitHub threads carrying 6 comments, fetched from w3c/wcag3 by the tracker. Titles, numbers and states are the threads' own.
What the Argument Is About
Nobody can say what "detectable" means — the disagreement is whether it needs a normative definition or whether the requirement should be dropped as redundant.
Positions taken in the thread
Calls "Non-decorative images are detectable" painfully vague and asks the specific questions the text cannot answer: detectable to whom, what counts as detectable, whether "screen users need to know that an image of text is an image", and whether the obligation is programmatic and if so over which part — role, accessible name, or both (#494). Observes that role and name already appear to be covered by other requirements, so if that is not what this means, nothing is left. Recommendation is to remove the requirement.
Agrees the term is ambiguous but proposes a fix rather than deletion (#605): "A detectable element is one that can be identified programmatically in code and is presented to users in a way they can perceive." Points out that the only place the concept is currently explained is the non-normative Test section, which is not a basis for consistent interpretation or enforcement.
Folding code inspection and screen reader inspection into one test case invites incorrect interpretation; JasonAment proposes splitting them into parallel tests with alternate conditions — check the markup where a code inspector can reach the image, and use a screen reader only where the code cannot be checked (#606). mraccess77 adds that the accessibility API should be checked before jumping to a screen reader test.
Raised as a review comment on PR 350 and carried into #357: does this forbid CSS background images unless they are also marked up as images, and how does it square with the decorative-image requirement that such images be programmatically hidden? If an image is hidden it cannot be determinable as an image, which suggests the requirement is really about images that convey meaning. scottaohara later confirmed the draft preview updates to both requirements addressed this, and adampage closed the issue on 2026-04-01 after verifying the editor's draft.
MakotoUeki asks whether "non-decorative images" can simply be defined as "images that convey meaning", and whether in HTML using an img element satisfies the requirement (#467). mraccess77 answers no: use of img does not by itself mean the image is anything other than purely decorative.
Pushes to revisit his "Meaningful images have a text alternative" proposal against the current draft's goal that users have equivalent alternatives for images (#272). Cites WebAIM's finding that nearly a third of images on popular home pages have missing, questionable or repetitive alternative text, and argues there is no agreement on what an "equivalent" even is — ask ten experts and get ten answers. Wants a more scalable, consistent approach that works without technology changes and adapts as technology shifts, and points to slides 11-17 of an earlier working-group presentation on inter-rater reliability.
Agreed
- "Detectable" as currently written is ambiguous — WilcoFiers and JasonAment reach that conclusion independently, and scottaohara's confusion about how it could be foundational, in the PR 350 review comment iadawn carried into #357, is the same complaint from a different angle.
- Presence of an img element does not establish that an image is non-decorative — mraccess77's answer to MakotoUeki was unrebutted.
- The detectable/decorative collision in #357 was resolved by the drafting changes in PR 414 and the issue is closed.
Still open
- Whether the requirement is defined or deleted — WilcoFiers wants it dropped, JasonAment wants a normative definition, and no one has replied to either.
- Whether "non-decorative images" should be restated as "images that convey meaning", as MakotoUeki proposes in #467.
- Whether the test is split into code-inspection and non-code-inspection branches, and whether an accessibility API check sits between code and screen reader as mraccess77 suggests (#606).
- mbgower's request in #272 for the group to revisit his alternative proposal drew no response in the thread.
Note
Six threads but only six comments across all of them: most of these are single unanswered review filings rather than exchanges. #357 is the one thread that ran to a conclusion, and it closed as resolved by drafting rather than by argument.
- #272 Requirements: Image alternatives open 2 comments · updated 2026-04-02
- #357 Detectable Image and CSS background images closed 2 comments · updated 2026-04-01
- #467 `img` element meet this requirement? - Detectable images (Foundational) open 1 comment · updated 2026-03-29
- #494 What does "detectable" mean in "Non-decorative images are detectable" open 0 comments · updated 2026-03-29
- #605 2.1.1 - Core requirement: Images detectable: "Detectable" is ambiguous and requires a definition. open 0 comments · updated 2026-03-27
- #606 2.1.1 - Core requirement: Images detectable - Test needs update open 1 comment · updated 2026-03-27
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.
No mapping recorded. No WCAG 2.2 criterion in this site's map is recorded as a predecessor of this provision.
Related WCAG 2.2 criteria
On a neighbouring subject, but this provision doesn't replace them.
W3C Raw Source Text
Verbatim from guidelines/groups/images-and-media/image-alternatives/images-detectable.md · informative document: informative/guidelines/images-and-media/image-alternatives/images-detectable.md
Non-decorative images are detectable. :::applies-when - content includes non-decorative images. :::