HumanFlow vs Undetectable.ai

Their pricing page publishes a monthly allowance — 10,000 words on the entry plan — and says nothing about how much you can put through in one paste. Ours publishes both numbers: 25,000 words a month on the $18 Writer plan, and 5,000 of them in a single request.

For most work the unstated one sounds better, and for short pieces it makes no difference either way. The distinction bites on a long document. If you are pushing a 6,000-word chapter through in one go, our plan tells you in advance that you will be doing it in two passes. Theirs tells you nothing, which means you find out by trying.

This is not a criticism of their product, it is a criticism of the disclosure. An unstated limit is not a promise that no limit exists — it is an absence of information, and we have marked it as one in the table above rather than reading it as unlimited. If they publish a figure, we will quote it.

Undetectable.ai sells AI detection alongside AI humanizing, and extends it to images and PDFs. So do we, on text. That arrangement has an obvious problem in both directions: the company scoring the output is the company that sold you the tool which produced it.

We handle it by publishing sentence-level results rather than one document-level verdict, so you can see where a detector's suspicion actually concentrates instead of taking a single number on trust, and by saying plainly on every page that our own detector is subject to the same limits as everyone else's. We have not seen Undetectable.ai address the conflict either way, which is not the same as saying they ignore it.

The practical advice is the same one we would give about our own tool: do not treat any vendor's detector as the arbiter of whether a vendor's humanizer worked. Run the text past something neither company owns.

Read on 15 August 2026, their pricing page lists "Passes AI detectors" as a feature of every paid tier. We are recording that as their claim, in their words, because a comparison page that hid it would be less useful than one that quotes it.

We do not make that claim, and the reason is not modesty. A statement about whether text passes a detector is a statement about the future behaviour of systems that change without notice, that disagree with each other on identical input, and that neither vendor controls or observes. Anyone publishing a pass rate is describing one snapshot against one detector version and presenting it as a property of their product.

If that claim is what you are buying, buy it from them — we have nothing competing to offer, and we would rather say so than imply we secretly do. What we will say is narrower and checkable: rewriting for rhythm and specificity tends to lower detection scores, because that is what detectors read as human. It is not a guarantee, and if your institution requires you to disclose AI assistance, a rewrite does not change that obligation.