Who this affects
Heading levels skip (h1 → h3 → h5). Screen reader users navigate by headings, and a broken outline makes the page hard to scan.
How to fix it
Use heading levels in sequence and style them with CSS rather than choosing a tag by its size.
Effort Low · ~30 min per template
Before and after
Fails
<h1>Kettles</h1>
<h4>Stainless steel</h4>Passes
<h1>Kettles</h1>
<h2>Stainless steel</h2>How to check it by hand
Use a heading-outline extension, or the screen reader's heading list. The outline should read like a table of contents. Levels that jump, or headings used for visual size, show up immediately here.
Automated testing settles roughly a third of the WCAG success criteria. This rule is one an automated tool detects reliably — but a clean automated result is not proof of conformance.
Reference
Deque's technical write-up for this rule: heading-order
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