What a keyword density checker actually measures
Keyword density is simply the percentage of words on a page that are a specific word or phrase, out of the total word count. If a 1,000-word article mentions "content marketing" fifteen times, and you're measuring the two-word phrase, the density is roughly 3%. On its own that number tells you nothing about rankings, but it is a fast, objective way to spot two very different problems: pages that never mention their own topic clearly enough for a reader (let alone a search engine) to understand what they're about, and pages that repeat a phrase so often it reads like it was written for a bot rather than a person.
This tool tokenizes your pasted text, strips punctuation, and optionally removes common stop words like "the", "and", and "of" so the frequency table isn't dominated by function words that appear in almost any sentence. You can switch between single words, two-word phrases and three-word phrases depending on whether you're checking a short-tail keyword like "shoes" or a long-tail phrase like "best running shoes for flat feet". The table below the terminal output shows the twenty-five most frequent phrases at your chosen length, ranked by raw count, with a density percentage next to each one so you can see at a glance which words are dominating your copy.
Reading the focus keyword score
If you enter a focus keyword, the tool calculates its density separately and gives it a plain-language badge. Densities roughly between 0.8% and 3% are treated as a healthy range for most long-form content — enough repetition that the topic is unmistakable, without tipping into the kind of unnatural repetition search engines have penalized for well over a decade. Below that range the badge flags the phrase as under-used, which is often a sign the page relies on synonyms and pronouns so heavily that neither a reader skimming the page nor a crawler parsing it can easily tell what the primary subject is. Above roughly 3% the badge switches to a stuffing warning, since natural writing rarely repeats an exact phrase that often without starting to sound repetitive out loud.
It's worth being clear about what this number is not. There is no official "optimal density" published by any search engine, and no single percentage guarantees a ranking improvement. Modern ranking systems evaluate topical relevance using far more sophisticated language understanding than a simple word count, looking at synonyms, related entities, and how naturally a topic is covered across a whole page. Density is best used as a sanity check during editing — a quick way to catch copy that has drifted too far in either direction — rather than a target to hit exactly.
How to use the results while editing
A practical workflow is to draft your content first without thinking about density at all, focused purely on answering the reader's question clearly. Once the draft is done, paste it in here, check the focus keyword score, and skim the phrase table for anything unexpected. It's common to discover a filler phrase like "in this article" or a brand name repeating far more than intended. Because everything runs in your browser with plain JavaScript, you can paste in draft after draft as you revise without waiting on a server or hitting a daily limit, which makes it practical to check density at multiple stages of the editing process rather than just once at the end.