What is the hierarchy of headings?

H1 is the page's single main topic, H2s mark its major sections, H3s break those sections into sub-points, and so on down to H6. Each level should nest under the one above it — skipping a level breaks the outline the same way skipping a step breaks a staircase.

What's the difference between a heading and a subheading?

A heading introduces a section; a subheading introduces a subsection within it. In HTML terms, a subheading is simply the next level down — an H3 is a subheading relative to the H2 it sits under.

What is a good heading structure?

One H1 that states the page's topic, followed by H2s for each major section in a logical order, with H3s used only to break down content within an H2 — never skipping from H1 straight to H3, and never using a heading level purely to get a certain font size.

How many H1 tags should a page have?

One. Even though HTML5 technically permits multiple H1s within separate sectioning elements, a single H1 remains the safe, standard practice — it gives both search engines and assistive technology one unambiguous statement of what the page is about.

What are H1 and H2 tags in SEO?

The H1 declares a page's primary topic and is one of the stronger on-page relevance signals Google reads. H2 tags mark the major sections beneath it, helping both Google and readers scan the page's structure without reading every word.

Heading Structure Checker: Fix Your H1

Headings are structure, not style

The most common misunderstanding about headings is treating them as a way to make text bigger. An H2 isn't "the second-largest text size" — it's a declaration that a new section has started. Search engines and screen readers both build an outline of a page purely from its heading tags, in order, before they ever look at the actual paragraph text. If that outline is wrong — skipped levels, multiple H1s, headings used only for visual weight — both audiences lose the structure they depend on to understand the page.

How the hierarchy is supposed to work

H1 — the page's single main topic. One per page.
H2 — a major section within that topic.
H3 — a sub-point within an H2 section.
H4–H6 — further nesting, rarely needed outside long, deeply structured documents.

Each level should nest directly under the one above it. Jumping from H1 straight to H3 — skipping H2 entirely — breaks the outline the same way skipping a stair step breaks a staircase: technically you can still get up it, but anyone relying on the structure (a screen reader user tabbing through headings, or Google building a summary) stumbles.

The same page, broken and fixed

Outlines are easier to judge visually than described. Here's a page with two of the most common structural mistakes stacked on top of each other:

H1  Running Shoe Reviews          <- fine, one topic
  H3  Best for Trail Running      <- skipped H2, gap in outline
  H3  Best for Road Running
  H1  Buying Guide                <- second H1, competes with the first
    H4  What to Look For          <- skipped H2 and H3 both

Two separate problems: the trail and road sections jump straight from H1 to H3, skipping H2 entirely, and a second H1 appears partway down the page — so a screen reader or crawler building this outline can't tell whether "Buying Guide" is a new top-level topic or a section of the shoe reviews. Flattened into a correct hierarchy, the same content looks like this:

H1  Running Shoe Reviews
  H2  Best for Trail Running
  H2  Best for Road Running
  H2  Buying Guide
    H3  What to Look For
    H3  Fit and Sizing

One H1, everything else nests directly under the level above it, and "What to Look For" and "Fit and Sizing" are now clearly sub-points of the buying guide rather than orphaned H4s with no H2 or H3 above them. Nothing about the visible page design has to change to fix this — heading level and font size are unrelated, so the fix is almost always just swapping tag names, not redesigning anything.

Paste a URL into CheckSEO's H1 Checker to see your page's full H1–H6 outline and every place it breaks — no signup.

Check your heading structure

5 heading mistakes that hurt both SEO and accessibility

Skipping heading levels

Going from H1 directly to H3 (or H2 to H4) leaves a gap in the outline. Screen reader users navigate by heading level specifically to skim a page's structure — a gap reads as a broken or incomplete document.

Multiple H1 tags on one page

Even though the HTML5 spec technically permits more than one H1 within separate sectioning elements, using several dilutes the single clearest signal of "what is this page actually about" — for both Google and a human skimming the page.

Headings used purely for font size

Wrapping a phone number or a call-to-action banner in an H2 just because it needs to look bigger pollutes the real outline with content that isn't actually a section heading. Use CSS for size, headings for structure.

No H1 at all

A page with no H1 has no single declared topic — Google has to infer one from the title tag and body content instead of being told directly, and screen reader users lose the one heading they'd normally jump to first.

Vague, non-descriptive headings

A section titled "More Info" or "Details" tells a skimming reader (or a search engine) nothing about what's actually there. Descriptive headings double as a genuinely useful table of contents.

Why this matters beyond rankings

Heading structure sits at the intersection of SEO and accessibility more directly than almost any other on-page element — the same outline that helps Google summarize a page is what a screen reader announces to a visually impaired visitor navigating by heading. Getting it right serves both audiences with the same fix, which is rare in SEO advice.

Concretely: most screen readers let a user pull up a list of every heading on the page and jump straight to any one of them, the same way a sighted user's eye jumps down a table of contents. A user who wants the "Buying Guide" section in the example above navigates there directly by heading, in under a second, without reading anything that comes before it. That shortcut only works if the heading text is descriptive and the level is correct — a heading list full of "More Info" entries, or one with a missing H1 so the list starts on an arbitrary H2, defeats the exact navigation pattern it exists to support. Google's own use of headings — building featured snippets and page outlines for search results — relies on the same structural signal for a different purpose, which is why a fix aimed at accessibility so often pays off in SEO at the same time.

Image alt text shares this exact overlap — it's another attribute a screen reader depends on directly and Google reads as a genuine content signal, not a formality. If you're fixing heading structure for accessibility reasons, alt text is usually the next thing worth checking on the same page.

Headings versus ARIA landmarks: different jobs

A related but distinct accessibility feature sometimes gets confused with headings: ARIA landmark roles (<nav>, <main>, <aside>, and their explicit role attribute equivalents) mark out a page's major regions — navigation, main content, sidebar — so a screen reader user can jump straight to, say, the main content and skip a repeated navigation menu on every page load. Headings mark out topics within the content itself. A well-built page uses both, and they're not interchangeable: wrapping your main content in <main> doesn't substitute for having a correct H1–H6 outline inside it, and a perfect heading outline doesn't help a user trying to skip past the header and navigation to reach that content in the first place. If you're auditing a page for accessibility rather than SEO specifically, checking both is worth the extra few minutes — they catch different failure modes.

Check your own page

CheckSEO's H1 Checker reads a page's full H1–H6 outline and flags skipped levels, missing H1s, and multiple-H1 pages in one pass.

Heading Structure and SEO: How H1–H6 Hierarchy Actually Works