Keyword density is a diagnostic, not a target to hit#
There is no ideal density percentage — Google has never confirmed one, and older advice to aim for "2-3%" is a myth left over from an earlier, more mechanical era of SEO. What density is actually useful for is noticing when a term is repeated so often it reads unnaturally, or conversely, when a page never actually uses the phrase it is supposedly targeting. This tool surfaces the numbers; the judgment about whether they look natural is still a human one.
Why stopwords are filtered from the single-word list, but not from phrases#
Without filtering, "the", "and", "is" and similar function words would dominate every single-word result on any page, telling you nothing useful. They are removed from the unigram list for that reason. Two- and three-word phrases keep them, because a real phrase like "how to convert" or "free online tool" naturally contains a stopword — stripping it would break the exact phrase a page is likely targeting.
Why only repeated phrases show up#
Any block of text longer than a sentence contains dozens of unique three-word sequences that only ever appear once — showing all of them would just be noise. Only phrases that repeat at least twice are listed, since a phrase appearing once is not really a density signal at all.