Headings are used to provide hierarchy and clarity to a web page. This helps visitors quickly scan the page and helps search engines understand its structure and topic.
There are six heading levels: H1 through H6. While headings only play a small role in search engines’ algorithms, including keywords in headings does contribute to topical relevance – and through that, improved rankings.
Headings should be logically structured on a page. A page starts with the H1 heading, followed by an H2 heading, which can be followed by an H3 heading should you need a sub-section. For the start of a new section, you should use another H2 heading. Don’t skip a level in the hierarchy; for example, don’t go from an H1 heading to an H3 heading. There should be an H2 heading in between them.
Here’s a good example of correct heading usage:
The H1 heading describes a page’s main topic. It should be highly related to the content and unique across your website, and a page may only contain one H1 heading.
Don’t put the H1 heading tags around an image, since search engines don’t understand images very well. You’d be missing out on an opportunity to signal to search engines what a page is about.
You should avoid making the H1 heading too long. If you do, there's a big chance the H1 heading won’t be readable for your visitors, which hurts their user experience. But there’s no minimum H1 heading length. Just make sure the H1 heading makes sense for your visitors. It should communicate the main topic of the page.
When the HTML5 specification was first introduced, support for multiple H1 headings per page (each in their own section-element) was included. However, since browsers didn’t adopt this recommendation, support for this was subsequently dropped when the HTML5.1 standard was published. For more information, see this W3c thread.
If you haven’t defined a page title, or if search engines didn’t find your title to be relevant enough, they may show the page’s H1 heading as the title in the page’s search engine result – its snippet.
H2–H6 headings are used to further structure the content. Using H2 headings is recommended, and using H3-H6 headings is optional.
Yes, they do! Even today, headings still play a role in communicating relevance for keywords to search engines.
While the role of headings in search engine algorithms has decreased over the years, it does send a clear signal to search engines regarding what a page is about.
From a visitor standpoint it can be, if another title or H1 heading is a better fit. From an SEO standpoint this is not a problem. It’s definitely not something you’d get penalized for by Google.