Table headers in a data table must refer to data cells

Rule ID: th-has-data-cells
Ruleset: axe-core 4.9
User Impact: Serious
Guidelines: WCAG 2.1 (A), WCAG 2.0 (A), WCAG 2.2 (A), Section 508, Trusted Tester, EN 301 549

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Compliance Data & Impact

User Impact

Serious
Minor
Critical

Disabilities Affected

  • Blind
  • Deafblind

Standard(s)

  • WCAG 2.1 (A)
  • WCAG 2.0 (A)
  • WCAG 2.2 (A)
  • Section 508
  • Trusted Tester
  • EN 301 549

WCAG Success Criteria [WCAG 2.1 (A)]

  • 1.3.1: MUST: Info and Relationships

WCAG Success Criteria [WCAG 2.0 (A)]

  • 1.3.1: MUST: Info and Relationships

WCAG Success Criteria [WCAG 2.2 (A)]

  • 1.3.1: MUST: Info and Relationships

Section 508 Guidelines

  • 1194.22: MUST: Web based intranet and Internet Information & Applications
  • 1194.22 (g): MUST: Row and column headers shall be identified for data tables.” and “(h) Markup shall be used to associate data cells and header cells for data tables that have two or more logical levels of row or column headers.

Trusted Tester Guidelines

  • 14.B: MUST: All data cells are programmatically associated with relevant headers.

    How to Fix the Problem

    Ensure that each table header in a data table refers to data cells so that each header cell that is used is actually a header of something.

    In other words, the th element must have associated data cells.

    If header attributes exist, ensure that they reference elements with text available to screen readers.

    • The th element must not use the headers attribute
    • th elements should only be used when there is a single row and single column of headers
    • th elements must use the scope attribute

    Bad Example: <th> with set to scope="row" instead of scope="col"

    Notice the <th> elements are scoped to row when they should be scoped to col in the following table:

    Teddy bear collectors:
    Last Name First Name City
    Phoenix Imari Henry
    Zeki Rome Min
    Apirka Kelly Brynn
    <table>
      <caption>Teddy bear collectors:</caption>
     <tr> 
        <th scope="row">Last Name</th>
        <th scope="row">First Name</th>
        <th scope="row">City</th>
      </tr>
      <tr>
        <td>Phoenix</td>
        <td>Imari</td>
        <td>Henry</td>
      </tr>
      <tr>
        <td>Zeki</td>
        <td>Rome</td>
        <td>Min</td>
      </tr>
      <tr>
        <td>Apirka</td>
        <td>Kelly</td>
        <td>Brynn</td>
      </tr>
    </table>

    Following is the corrected code for associating column headers with table content in the previous example:

    ...
    <th scope="col">Last Name</th>
    <th scope="col">First Name</th>
    <th scope="col">City</th>
    ...
    

    Why it Matters

    Screen readers have a specific way of announcing tables. When tables are not properly marked up, this creates the opportunity for confusing or inaccurate screen reader output.

    When tables are not marked up semantically and do not have the correct header structure, screen reader users cannot correctly perceive the relationships between the cells and their contents visually.

    Rule Description

    Data table markup can be tedious and confusing. Markup tables semantically and with the correct header structure. Screen readers have features to ease table navigation, but tables must be marked up accurately for these features to work correctly.

    The Algorithm (in simple terms)

    Checks data tables markup, ensuring each header cell is referenced as a header of a column or row.

    Resources

    Refer to the complete list of axe 4.9 rules.

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