AI Humanizer vs QuillBot vs Grammarly: Which One Do You Actually Need? (2026)

People use these three tool names interchangeably. "I need something like Grammarly to beat Turnitin." "Can QuillBot humanize my AI text?" "Is an AI humanizer just a fancy paraphraser?"

They are three tools that do three different jobs. Here is what each one does, what each one costs, and — the part most comparisons skip — why the question you probably came here with does not have an honest answer.

The question this post cannot answer

If you are here to find out which tool gets you past Turnitin, no page on the internet can tell you, and any page that does is either guessing or repeating a vendor.

An earlier version of this page did exactly that. It published a table: a 500-word ChatGPT essay run through each tool, scored on Turnitin, GPTZero and our own detector, six conditions, eighteen numbers. It reported the original at 97% AI, then 94% after Grammarly, 72% after QuillBot Standard, 12% after our own humanizer and 5% after ten more minutes of editing — every one of those numbers invented, and arranged as a clean descending line ending at our own product, which is how you can tell what they were for.

That test was never run. It could not have been. Turnitin has no public API, and every detector in that table forbids in its terms the automated submission such a test requires. The numbers were invented, and they were invented in the direction that sold our own product. They are gone, along with the advice that went with them about which score keeps a professor from looking closer.

We publish the error rates of our own detector, including a 96% false negative rate, at /ai-detector/accuracy. We publish nothing about anyone else's, because we have no way to obtain it.

What each tool actually does

Grammarly: grammar, spelling, tone

Grammarly checks grammar, spelling and punctuation, and on the paid tier style and tone. That is its job and it is the most deeply integrated tool of the three — it runs as you type, everywhere you type.

What it does not do is change sentence structure or word-choice patterns. Run AI-generated text through it and you get the same text with the commas fixed. If someone told you Grammarly helps with AI detection, they were wrong about what it is.

QuillBot: paraphrasing

QuillBot rewrites text in different words and structures while preserving meaning. Paste a paragraph, pick a mode, get a rewrite. Its actual strength is academic paraphrasing: rewording a source for a paper without plagiarising it — a different problem from AI detection, though students routinely conflate the two.

Does paraphrasing change a detector's score? Mechanically it must change something, since detectors score surface features. By how much, in which direction, on which detector, we do not know and neither does anyone quoting a number at you.

Coda One AI Humanizer: rewriting for readability

Our humanizer rewrites text so it reads less like machine output: varied sentence length, less predictable phrasing, fewer of the stock connectives and structures our detector's tells reference documents.

That is a claim about how the text reads. It is not a claim about what a third-party detector will say about it, and we do not make that claim anywhere any more. If you want to know what changed, run the before and after through our detector and read the sentence-level marks — which tells you about our detector, and only ours.

Feature comparison

Verified against each vendor's own pages on 2026-08-29 and recorded in this repository. Prices move; check before you buy.

Two notes on that table, because both were wrong here before:

Grammarly's headline price is $30/mo, not $12. $12 is the annual rate divided by twelve. The old version of this page printed $12 as the monthly price, which made Grammarly look 2.5× cheaper than it is.

QuillBot is the cheapest of the three, not the most expensive. The old version printed $9.95/mo. The real annual list rate is $4.17/mo, and there is a promotion at $2.50/mo running to 6 September 2026. We were publishing a competitor's price at more than double, on a page comparing them to us.

When to use which

Grammar, everywhere, as you type: Grammarly. Nothing else here is real-time.

Rewording a source for a paper: QuillBot. It is purpose-built for faithful paraphrase and it is the cheapest of the three.

Checking whether your own draft reads as machine-written, and fixing the parts that do: our detector and humanizer. The detector is free with no signup and no daily cap, so you can test this claim without paying us.

Getting AI text past a university's integrity check: no tool on this page, and no tool anywhere, can promise you that. The tools that promise it are the ones to distrust most.

The honest take

Grammarly is the best grammar checker and should not be evaluated as anything else. QuillBot is the best paraphraser and the cheapest of the three. Our humanizer rewrites text to read more naturally, and our detector shows you which sentences read like a machine and why.

Beyond that, we do not know how these tools rank against each other on detection, and neither does anyone else outside the detector companies. The honest version of this comparison is shorter and less useful than the version with the invented table in it. It is also the only one either of us can check.