Header tags are the HTML elements H1 through H6 that give a page its structure. The H1 states what the page is about, H2s divide it into major sections, and H3s and below break those sections down further. Used well, they make a page scannable for readers, navigable for screen reader users, and legible for search engines trying to work out what each section covers. They are a core piece of on-page work, and one of the easiest to get quietly wrong.
The short version
- Header tags create a page outline from H1 (main topic) to H6 (finest detail).
- Use one H1 per page and keep the levels in order, never skipping from H1 to H3.
- Most content only needs H1, H2, and H3.
- Headings are structure, not styling. Never pick a level for its font size.
- 1 H1 tag per page is the working rule
- 6 heading levels exist in HTML
- 36% of pages audited have H1 problems
- 70% of users scan a page before reading it
How the six levels fit together
- H1 is the main page title. One per page, carrying the primary topic.
- H2 marks the major sections. Multiple allowed, and this is where secondary keywords tend to sit naturally.
- H3 breaks an H2 section into subtopics.
- H4 handles detail under an H3, mostly in long technical material.
- H5 and H6 almost never appear outside dense documentation.
If you find yourself reaching for H4 and beyond regularly, the honest fix is usually restructuring the content or splitting the page, not going deeper into the outline.
Why the structure matters to search engines
Google reads headings to understand how a page is organized and what each section is about. Text in headings carries more interpretive weight than body text, and H2 or H3 content phrased as a question is a common source for featured snippets. Screen readers use the same outline as a table of contents, jumping heading to heading, which is why a skipped level or a decorative H3 is not a cosmetic problem. And since around 70% of visitors scan before they commit to reading, headings are also how a page earns the read at all.
The rules that keep headings working
- One H1 per page, containing the primary topic. The long answer to the multiple-H1 debate is in our post on whether multiple H1 tags are ok.
- Keep the hierarchy in order. H2 follows H1, H3 follows H2. Skipping levels breaks the outline for assistive tech.
- Make each heading describe its section. A heading is a promise about the text below it. Keep the promise.
- Keep headings unique on the page. Two sections titled the same thing help no one decide where to look.
- Write for the scan. A reader should be able to reconstruct the argument of the page from the headings alone.
The markup itself is as simple as HTML gets:
<h1>What is on-page SEO</h1>
<h2>The elements that matter most</h2>
<h3>Title tags</h3>
<h3>Headings</h3>
<h2>How to audit your pages</h2>The mistakes we find most in audits
- The H1 is the site logo or the brand name on every page, so every page claims the same topic.
- Levels chosen for font size, producing outlines like H1 to H4 to H2.
- Headings that are labels ("Overview", "More info") instead of statements about the content.
- Every heading stuffed with the same keyword, which reads as spam and scans terribly.
- No headings at all, just walls of bolded text that assistive tech cannot navigate.
A crawler like Screaming Frog lists every page's H1s in one report, and the free HeadingsMap browser extension draws the outline of any page you are viewing. Ten minutes with either tool finds most of the problems above.
Where headings fit in the bigger picture
Headings work alongside your title tag, which does the same job in search results that the H1 does on the page. Both are part of on-page SEO, and both reward the same discipline: say what the content actually is, front-load what matters, and resist the urge to decorate.
Questions people ask about header tags
What are header tags in SEO?
Header tags are the HTML elements H1 through H6 that define the heading structure of a page. They tell search engines which text matters most and how the content is organized, and screen readers use them as a navigation map.
How many H1 tags should a page have?
One. HTML5 technically allows more, and Google says rankings survive either way, but a single H1 keeps the main topic of the page unambiguous for crawlers, screen readers, and anyone skimming. Use H2 tags for major sections instead.
Do header tags affect rankings?
They carry some weight. Headings help Google understand what each section covers, and heading text is a common source for featured snippets. The bigger effect is indirect: pages people can scan hold attention better, and clear structure is part of that.
Should headings contain keywords?
When it reads naturally, yes. A heading should first describe its section accurately; if the target keyword belongs in that description, include it. Forcing exact-match keywords into every heading reads as spam and has not worked in years.
Can I use header tags just to make text bigger?
No. Headings are structure, not styling. If you want large text without a new section, use CSS. Using an H3 because you like its font size breaks the document outline that screen readers and crawlers depend on.
