An H1 is a page’s main heading, and each page should have one. Several H1s make it less clear what the page is about.
Why Joomla sites get it
On a single-article page, Joomla’s article layout already prints the article title as the H1 (unless the menu item’s Show Page Heading is on, in which case the page heading is the H1). Any H1 inside the article text is therefore a second one. They usually arrive with text pasted from Word or Google Docs, where the first heading is formatted as Heading 1, or from an editor’s paragraph menu.
Fix it by hand
- Open the article in the editor.
- Change each heading formatted as Heading 1 to Heading 2 (and move the headings under it down a level if needed).
- Save.
Fix it with MetaGen
MetaGen’s Multiple H1 tags row counts articles with more than one H1, including an H1 in the text of an article whose template already shows the title as the H1. Fix turns the extras into H2 across every affected article, and records each change.
MetaGen is free for Joomla 5 and 6. See all the SEO warnings MetaGen checks.