Heading Structure Checker

Headings are not styling — they are the document outline, and screen reader users navigate by them the way sighted readers navigate by scanning. Jumping from an H2 straight to an H4 leaves a gap in that outline, so someone moving through headings hears a level that appears to belong to a section that does not exist. WCAG treats skipped levels as a genuine accessibility failure rather than a stylistic preference.

The conventional rules are worth following even where nothing enforces them: one H1 per page describing the whole page, H2s for major sections, H3s nested inside them, and no level skipped on the way down. Going back up is fine — an H3 followed by the next H2 is normal — it is only descending by more than one that breaks the structure. Choose the level for hierarchy and control the size with CSS, never the reverse.

Structural problems in headings almost always reflect structural problems in the writing. A page with fourteen H2s and no H3s usually has no grouping at all; a page that never descends past H2 in a 3,000-word guide is a flat list of topics that a reader cannot orient within. Fixing the heading levels tends to force the underlying reorganisation, which is why this check is worth running before line editing rather than after.