Writing that is hard to read usually fails in a specific and fixable way. Sentences grow longer as an argument develops, subordinate clauses stack up, and ordinary words get replaced by impressive ones. The result still contains everything it started with, and considerably fewer people finish it.
What the analyzer measures
Readability, mostly through sentence length and word difficulty. Long sentences are the strongest signal, because a reader has to hold several ideas in mind at once, and a sentence carrying four points loses most of them. Difficult words matter too, particularly when a plainer word would carry exactly the same meaning.
The tone check is separate and more limited. It looks at indicators of register, such as whether the language is formal or conversational and how consistently it holds that register. It cannot judge whether your argument works, whether your evidence supports your claim, or whether the piece is any good. Read those as signals about the surface rather than as an assessment.
Interpreting the number
Scores map roughly onto education levels, which is a reasonable shorthand for general audiences. For a blog or a product page, writing for a wide audience means keeping sentences shorter than feels natural to you. Professional writers consistently underestimate how long their sentences get.
The number is a guide rather than a verdict. Technical documentation with complex subject matter will always score higher, and that is fine. What matters is knowing when a score is high because the material is genuinely difficult and when it is high because the writing is doing something needlessly clever.
The changes that actually help
Split the longest sentences first. Replace the most complicated word in each with a shorter one that means the same thing. Delete the transition words that are not doing any work, because most transitions already follow naturally.
Then read the result aloud. Sentences that are difficult to say are difficult to read, and this catches far more than the score does.
Privacy
The analysis runs in your browser, so unpublished writing stays on your machine. That is the reason to use a local tool rather than pasting a draft into a website you have no control over.
Try next
Related guide: free text to speech online
What it cannot tell you
It is worth being clear about the limits, because a score invites over-trust. Readability says nothing about whether your argument holds together. A perfectly clear sentence can contain a claim that is wrong, and tightening it will not fix that.
It also cannot judge tone with any subtlety. Formal and conversational registers are easy to detect, but whether your tone suits your audience, your subject and the moment you are writing in, is a judgement the tool has no way to make. A support reply that is too formal and a legal notice that is too casual are both perfectly readable.
Nor does it measure interest, clarity of argument or originality, which are the qualities that decide whether anyone finishes and remembers what they read. A high score means the sentences are easy to get through. That is a real contribution and it is not the whole job.
Use it as a first pass that finds the awkward sentences, then make the judgement calls yourself. Editing is a craft and this is a pointer to the paragraphs that need attention, not a verdict on the draft.