ACT Rule a25f45
Headers attribute specified on a cell refers to cells in the same table element
In a complicated table a cell can name its own header cells by id, using the headers attribute. This rule checks that the ids it names are real cells inside the same table.
A tool can decide this one on its own, which is why it turns up in scanner output. The rule is approved, which in W3C's process means it was implemented in full by at least one tool or methodology and then signed off by a working group. Approval is a statement about tools, not a statement that this is the settled way to test the criterion.
What passing this rule proves
When this rule fails, 1.3.1 Info and Relationships is not satisfied, and that half is certain. When it passes, W3C's own outcome mapping says the criterion still needs further testing. So a green result here is evidence that one specific thing is not broken, and it is the answer W3C gives on 59 of its 87 live rules.
W3C uses a rule very like this one as its own worked example of what a test rule cannot do. Checking that a header reference resolves is not checking that the table is marked up correctly, and it is nowhere near checking that the structure matches what a sighted reader sees. The criterion covers every structural relationship on the page. Read a couple of rows with a screen reader and you will know in two minutes.
The criteria this rule is a test for
These are the criteria the rule names as its own conformance requirement. Each one is a far bigger question than this rule asks, and our page for it sets out what the whole criterion covers.
- 1.3.1 Info and Relationships Level A
The normative rule text lives at W3C
What the rule applies to, and exactly what it expects, is published by W3C and can change. We link to it rather than restate it, so nothing here can quietly fall out of date against the source. Read rule a25f45 at W3C.
Table headers must point at the right cells
Sighted readers work out a table from its shape. Assistive technology cannot so it relies on the markup saying which cell heads which column or row.
When a header points at nothing or at cells in a different table, every value under it is announced without its label. The numbers are read out with no idea what they measure.
Hand-written headers attributes drift as a table changes. Split or merged cells are where they usually stop matching. The headers no longer point at the right cells.
Fixes that satisfy it
If this rule fails on your site, these are the techniques that put it right.
Other rules W3C files under the same criteria
Each of these asks a different question about the same part of the standard. Passing all of them is still not the same as satisfying the criterion.
- ARIA attribute is defined in WAI-ARIA A tool can check this
- ARIA state or property has valid value A tool can check this
- Element with role attribute has required states and properties A tool can check this
- Form field has non-empty accessible name A tool can check this
- Role attribute has valid value A tool can check this
- ARIA global properties not used where prohibited A tool can check this
All 87 ACT rules are grouped by the criteria they test, and 24 of them decide nothing about WCAG on their own. Run a free scan to see which of these your own pages trip.