There isn't a singular "best" keyword density for SEO that can be universally applied to every content and website. In the realm of modern SEO, the significance of keyword density as an isolated metric has diminished progressively. Nowadays, the emphasis leans more towards crafting high-quality, user-centred content that genuinely benefits your audience by honing in on specific topics. Search engines such as Google have advanced, considering a broader spectrum of factors beyond mere keyword density to ascertain a page's relevance and ranking.