Define proper table headers

Rule Details

Table headers (<th>) are essential for providing context to the data contained within table cells.

Code Example

<table>
  <caption>Weekly Team Schedule</caption>
  <thead>
    <tr>
      <th scope="col">Name</th>
      <th scope="col">Monday</th>
      <th scope="col">Tuesday</th>
    </tr>
  </thead>
  <tbody>
    <tr>
      <th scope="row">Alice</th>
      <td>9:00 - 5:00</td>
      <td>9:00 - 5:00</td>
    </tr>
  </tbody>
</table>

Why It Matters

• Context for Assistive Tech: Screen readers announce the header text when a user navigates to a data cell.
• Visual Distinction: Headers are typically styled differently (bold and centered) by browsers.
• Navigation: Users of assistive technology can jump between headers to scan the content.
• Data Integrity: Clearly defines the relationship between categories and their values.

Exceptions

• Simple data tables can sometimes fail more from missing header relationships than from missing enhancements such as captions or mobile wrappers, so prioritize the strongest semantic issue.
• Do not convert layout structures into data-table markup just to satisfy a rule; the correct fix may be to remove table semantics entirely.
• When several table-accessibility issues overlap, resolve the header-cell relationship first because downstream announcements depend on it.

Verification

Automated Checks

• Inspect the browser accessibility tree or accessibility pane for the relevant element, role, or accessible name.
• Run an automated accessibility checker such as axe or Lighthouse where applicable.

Manual Checks

• Test the affected UI with keyboard-only navigation and confirm the rule holds in the rendered experience.
• Re-test one representative user flow with a screen reader if this rule affects a key interaction.