A subheading is a heading that sits below a page’s main title and labels one section of the content. On the web, subheadings are normally marked up as H2, H3 and lower heading tags, so they carry meaning for browsers, screen readers and search engines as well as for the eye.
How subheadings work
A page has one main heading, the H1, which says what the whole page is about. Each major section beneath it gets an H2. If a section has distinct parts, those get H3s inside it. The result is an outline, like the contents page of a report, that you can read on its own and understand.
A note on terms. In UK publishing, the summary sentence that sits directly under a headline, setting up the article, is called a standfirst (American publishers call it a dek). It is not a subheading in the structural sense, and it should usually be a paragraph rather than a heading tag. Some marketers also use “subheadline” for the supporting line under a landing page headline; again, that is display copy rather than a section label.
Visually, a subheading should look like a heading: bigger or bolder than body text, with space above it. But the tag, not the styling, is what tells software where sections begin. A line of bold text that looks like a heading but is coded as a paragraph is invisible as structure.
Why it matters
Most people scan a web page before deciding whether to read it. Subheadings are what they scan. Good ones let a visitor jump straight to pricing, the process or the answer to their question, which keeps them on your page instead of back at the search results. That makes subheadings one of the cheapest ways to improve readability.
They matter for accessibility too. Many screen reader users move through a page by jumping from heading to heading. If your sections are not marked up as headings, or the levels jump about, the page is much harder to use. Logical headings support the WCAG guidelines, which UK public sector websites must meet and which are the usual benchmark for showing that a private business has made reasonable adjustments under the Equality Act 2010.
For search, subheadings help Google understand what each part of a page covers. A clear question-style subheading followed by a direct answer is a common pattern behind featured snippets, and well-labelled sections are easier for AI search tools to extract and cite.
Common mistakes
- Choosing heading levels for their size rather than their place in the outline, such as an H4 straight after the H1.
- Vague labels like “Overview”, “More information” or “Our approach” that could sit on any page.
- Witty subheadings that make sense only after reading the section.
- Stuffing the same search term into every subheading, which reads badly and helps nothing.
- Website themes that code sidebar titles, footer labels or card titles as H2s, cluttering the outline.
- Sections of 800 words with no subheading at all.
How to act on it
Take one important page and list its headings in order, using a browser extension or an SEO crawler. Read the list without the body text. If someone could not tell what the page covers and in what order, rewrite the subheadings until they could.
Write each one to describe its section specifically: “What a survey costs in London” beats “Pricing”. Use your audience’s words, and where a section answers a common question, it is fine to phrase the subheading as that question. Check that levels run in order with no skipped steps, then fix any theme elements that wrongly use heading tags.
Headings and their structure are among the first things I review in on-page SEO work, because fixing them improves a page for visitors, assistive technology and search engines at the same time.