Header tags — such as H1, H2, and so on — are one of several elements that affect on-page search engine optimization (or SEO). Headers are one element that can have an impact on both the user experience of your site and how the search engines process and interpret your content. Using header tags well requires that the writer understand how to create a pleasant read for the user, while also writing in language that search engines can understand and categorize with ease.
Headers appear in a page’s source code as tags such as <h1> or <h2>. They can take guidance from default style or from your website’s CSS. In general, applying a header tag to a piece of text will make it bigger and bolder, helping it to stand out more visually, while designating the visual accent in simple terms that search engines can recognize and understand. Unlike humans, search engines don’t “see” web pages in the visual sense. They use HTML code to interpret elements that change the look of the page, as well as to indicate which words and phrases are being used as titles, subtitles, and in other contexts. This also helps the search engines index content correctly.
You can use header tags in your HTML to add titles to the tops of articles and break up text with subtitles or subheaders. This adds visual breaks to a page, while also helping search engines understand the context of the words more clearly.
HTML contains six header tags, H1 through H6. H1 is the most prominent of the header tags — making it ideal to use for web page titles — and the tags get subsequently smaller and less prominent from there.
These are examples of what the various header tags could look like, however their appearance is dependent on your website's CSS.
When pages are indexed by search engine bots, the underlying HTML code is stored on the search engine’s servers to be analyzed and interpreted by their algorithm. This is how search queries get matched to web results so quickly. Header tags are an important piece of code that search engines will look at when trying to determine what keywords your content should rank for, how content on a page is organized, and what sort of topics your domain is about.
Ultimately, header tags are an essential feature of good content, and good content is essential to making other SEO strategies, such as link building, successful.
H1 tags are almost as important as title tags, but are subtly different. While title tags will display on a SERP, the H1 will generally appear at the top of the page when someone clicks on a result. Outside of the SERP, human readers generally won’t see or interact with a page’s title tag, but they are almost certainly going to see the on-page title (H1).
As such, H1 tags have a high priority when it comes to on-page SEO value. A search engine will look to the language between your H1 tags and title tags first, when trying to determine what a given page is about. It’s helpful for H1 tags to match your target keywords exactly where possible. However, H1 tags are also one of the most prominent elements on a page from the user’s perspective. Writing good H1 tags is an art that blends keyword matching with a sensitivity for a pleasant and humanizing user experience.
Header tags progressively lose SEO value with each step down. H2 tags are extremely important for establishing context and matching keywords to your content. Use H2 tags to signal keywords or specific blocks of content. It’s a good idea to match your H2 tags to your target keywords whenever possible and whenever it doesn’t disrupt the user experience.
H3 tags are still somewhat important for signaling keyword relevance, but this is the point at which the SEO value of header tags really starts to fall off. H3 tags are roughly on par with bolded text when it comes to signalling context and keyword matches. H3 tags can contain target keywords, but it’s best to leave most of the heavy keyword lifting to higher headings and subheadings.
Subheaders beyond H3 (i.e. H4, H5, and H6) don’t carry much SEO value when it comes to highlighting keywords. It’s fine if you find yourself writing content that contains these subheadings, but when you use them, remember that you’re using them more for the sake of the user experience, rather than for their SEO value.
