Is It Compliant?
Having multiple <h1> tags on a page is compliant syntax
According to MDN: “Although using multiple <h1> tags on a page is accepted by HTML standards,” and based on the W3C Markup Validation Service, having multiple <h1> tags on a page is 100% compliant syntax.
Is It a Good Practice?
MDN also mentions that “multiple <h1> elements should be avoided on the same page” because a page typically only has one <h1> to describe the content of the webpage.
However, Google, which has over 90% market share among search engines, states that “multiple <h1> tags do not affect search engine interpretation,” and we should focus more on the overall structure of the webpage. If regular website users can understand it, then search engines can too.
So what’s the conclusion…?
No definitive conclusion; the key is whether the overall title structure is reasonable when using multiple <h1> tags
The focus is not on “whether to use multiple <h1> tags” but on “whether users can understand the structure of the webpage.” If the webpage structure is clear and reasonable, then using multiple <h1> tags will not affect SEO. It’s quite rare to have many “major headings” on a single page, and if it’s reasonable in terms of reading structure, using multiple <h1> tags on a single page is perfectly fine.