The most necessary heading tag is that the h1 tag and least necessary is that the h6 tag. In hypertext mark-up language committal to writing, the heading tags from h1 to h6 kind a top-down hierarchy. this suggests that if you skip any of the tag numbers the heading structure are going to be broken, that isn't ideal for on-page SEO.
For example, if your website is introduced with associate degree h1 tag followed by associate degree h3 tag, the hierarchy are going to be broken, which means the heading structure isn't as SEO-friendly. this does not apply, however, to the bottom-up structure, that may jump from associate degree h4 to associate degree h2 while not issue. Ideally, each page ought to have associate degree h1 tag, however ne'er over one.