An H1 is the primary heading on a webpage, usually the most prominent title that describes what the page is about. In HTML, it is marked up with the h1 tag and it helps both users and search engines understand the main topic of the page at a glance.
For SEO, the H1 is not a magic ranking lever on its own, but it does matter for clarity and relevance. A strong H1 aligns with the core keyword theme of the page, sets expectations for the content, and supports good user experience. It also helps search engines confirm the page topic alongside other signals like the title tag, URL, and on page copy.
Best practice is to use one clear H1 per page, keep it descriptive, and avoid stuffing it with awkward variations. Think of the H1 as the page headline that should make immediate sense to a human reader.