What Google says about headings
Google's SEO starter guide is relaxed about this: there's "no magical, ideal amount of headings a given page should have", and from Google Search's perspective "it doesn't matter if you're using them out of order". Headings still matter in two places.
Title links: Google lists heading elements such as h1 among the sources it may use to write the title shown in results, and suggests making the main title the most prominent text, for example the first visible h1 on the page.
Accessibility: screen reader users jump between headings to scan a page. The W3C's accessibility tutorial says skipping heading ranks "can be confusing and should be avoided where possible", for example an h2 followed directly by an h4.
What each flag means
- No H1: the page has no main heading. Often a theme that styles the post title as a div or puts the title in an image.
- More than one H1: allowed in HTML and not a Google problem, but usually a sign the logo or sidebar uses h1. One clear main heading is easier for everyone.
- Skipped level: a heading more than one level deeper than the one before it, such as H2 followed by H4. Going back up (H4 to H2) is fine.
- Empty heading: a heading tag with no text or image alt text, often left by a page builder.
- Long H1: over 70 characters. Not an error, but a long H1 is usually a sentence rather than a heading.
Reading the outline
The outline is built from the HTML as it was sent to us, without running JavaScript. If your headings are added by scripts, the full scan renders the page in a browser and checks them there.
Headings in the header, sidebar and footer count too; that's what a screen reader or crawler sees. Theme widgets that use h2 for every box title are a common source of noise.