Best keyword density checkers compared, and the number none of them should make you chase
What a density checker counts, which free ones are worth opening, and the four checks to run on the same page instead once you have the number.
Published by AI Knows Us · Updated 21 October 2026
A keyword density checker fetches a page, counts words, and reports which terms and phrases appear most often and what share of the text each one takes. That is all it does, and it does it accurately. The useful question is not which checker is best at counting but what you are supposed to do with the count, because there is no density percentage to aim for and there has not been one for many years.
So this page ranks the checkers on a stated criterion: does the tool show you the phrase list and the page's own structure rather than a score it invented? A tool that hands you the terms it found, in order, with the headings and the title beside them, is doing the job. A tool that gives you a grade out of 100 and a target percentage is selling confidence instead of data.
The checkers, compared on what they return
| Checker | What you get | Judgement |
|---|---|---|
| SEO Review Tools keyword density checker | Single word, two word and three word phrase counts with percentages, for a URL or pasted text | The most direct free answer to the literal question. It returns a phrase list rather than a verdict, which is the right output. |
| SEO Book keyword density analyzer | A long established term frequency table with phrase grouping | Still useful for the raw counts. Check what it asks for before you use it, because an older free tool's access terms and transport can change without an announcement. |
| A browser view source and a text editor | Exactly what is on the page, with no intermediary | Faster than any tool for one page, and it is the only method that shows you what the words are doing in context rather than how many there are. |
| A content optimiser | The terms and subtopics shared by the pages currently ranking | This is the paid version of the job and the only version that compares your page with anything. Density alone compares your page with itself. |
Why the percentage is the least useful number on the report
Density is a ratio of counts in one document. A search engine ranks your document against other documents for a query, which means the question is never how often you said the phrase but whether your page answers the thing that was asked better than the pages above you. Two pages with identical density can rank thirty positions apart.
The practical rule is boring and it works. Use the phrase once in the title, once in the first paragraph and once in a heading where it reads naturally, then write for the person reading. If a tool tells you to raise a term from 1.1% to 2.4%, it is describing its own arithmetic rather than anything Google publishes.
The four checks worth running on the same page instead
Once the density report is open, these are the four findings on the same page that actually change outcomes, in order:
First, is the page indexed at all? Search Console URL Inspection answers it and nothing below matters until it does. Second, does the first paragraph answer the query in two sentences? This is the single edit that moves pages most often and it takes ten minutes. Third, what do the three pages ranking above you cover that yours does not? Read them properly rather than reading their titles. Fourth, does anything link to the page from your own site with a descriptive anchor? A page nothing points at is competing with one hand tied.
What a density checker is not looking at, and the tool that is
Every tool on this page reads your own HTML. None of them reads what an assistant says about you, and that is now part of the same buying decision, because a buyer asking who to buy from increasingly asks an app rather than typing a query and scanning a list.
AI Knows Us covers that one thing and nothing else on this page. The questions are yours, the apps are ChatGPT, Gemini, Perplexity, Claude and Google AI Overviews, and the output is the list of businesses each answer named. The cost is published in credits on our pricing page, where a credit means one question put to one app on one occasion, and a Claude check is counted as three of them because Claude costs more to run. We do not sell a density checker, a crawler or a content optimiser, and if that is what you came for the table above is the answer. Ahrefs reads more surfaces than we do, including AI Mode and Copilot which we do not read, and publishes its own per engine cost of 8 checks per update for a Claude check on its Brand Radar page.
The oldest free tool in this niche has a wrinkle worth knowing before you paste a client URL into it, and we wrote it up: the SEO Book keyword density analyzer, what it asks for now and how it is served. Across 1,655 tracked pages on this site, measured on 21 October 2026, 696 had no durable inbound link at all. That page was one of them at 390 searches a month, which is why it is linked from here.
What people ask about keyword density and the tools that measure it
What is a good keyword density?
There is no number to hit. Write the phrase where it belongs and stop counting. If you want a sanity check, read the page aloud: repetition that a tool would call optimal usually sounds wrong in your own voice.
Can high density get a page penalised?
Stuffing is a documented spam pattern and the fix is rewriting rather than tuning a percentage down by half a point. The patterns that cause trouble are lists of city names, repeated commercial phrases and text written for a counter instead of a reader.
Does density matter for long documents?
Less than for short ones, because the ratio falls as the page grows while the page gets better. That is the clearest demonstration that the metric is measuring the wrong thing: a page can improve and its density can drop at the same time.
Which free density tool should I use?
Any of them. They count the same words. Pick the one whose output you can read quickly and spend the saved time reading the pages that currently outrank you, because that comparison is where the next edit comes from.
Do assistants care about keyword density?
An assistant is composing an answer from sources rather than scoring your HTML, so what gets you named is being a source worth quoting on the specific question. The way to find out whether that is happening is to ask the question in each app and read who it names.