AI rewriter: what actually changes

Most rewriting tools do one of two things. One of them barely changes anything, and it is the one most tools do.

Rewriting tools split into two camps. Either they swap words for synonyms, or they rebuild the sentence. The first is cheap, common, and usually makes writing worse. The second is harder and is the only one that changes how a text actually reads.

Work out which one you are using and you know most of what there is to know about it.

Synonym swapping, and why it fails

The cheap version keeps your sentence exactly as it was and changes the words in it. "The results demonstrate a significant improvement" comes back as "The findings illustrate a considerable enhancement."

Three things go wrong at once.

The meaning drifts. Synonyms are almost never equivalent. "Considerable" and "significant" are different claims in a paper, where significance is a statistical statement. That swap changed what the sentence asserts, and nothing flagged it.

The rhythm survives untouched. Sentence length, clause order, paragraph shape, all identical. Those are the properties detectors weigh most heavily, which is why substitution often leaves a text scoring roughly what it scored before. More in why paraphrasing tools do not reduce detection.

Collocations break. Language runs on conventional pairings. "Conduct research" is idiomatic. "Administer research" is not, and a thesaurus will happily offer it. Enough of those and your prose reads as translated rather than written.

What a real rewrite touches

Rewriting that changes how something reads works above the word level:

Sentence length starts varying. Uniform sentence length is the single most reliable

signal that text was generated. Human writing alternates. Long qualified sentence, then a short one.

Clause order moves. Where the subject sits, whether the condition leads or trails,

whether two ideas share a sentence or split into two.

The connectives go. Generated prose signposts constantly. "Moreover", "Furthermore",

"Additionally", "It is important to note that." Cutting them usually improves the writing on its own merits.

Hedges get resolved. "May potentially suggest" becomes "suggests", or becomes a claim

with a stated limit next to it.

The specific markers are in what makes text read as machine written.

The bit that has to survive

Rewriting technical writing has a constraint general rewriting does not: the claims have to come through intact.

Anything carrying a value must survive untouched. Numbers, units, statistical results, p-values, sample sizes, citations, DOIs, URLs, equation references, defined terms. A rewrite that turns "42 samples" into "over forty samples", or quietly renumbers a citation, has changed what the paper says rather than how it says it.

This is where most general-purpose tools fall over, because they treat every token as equally rewritable. Ours marks those values as protected and rejects any rewrite that would alter one, which is why it will sometimes hand a paragraph back exactly as you gave it. We would rather refuse than damage a claim, and a paragraph that still reads a bit generated is a much smaller problem than a paragraph whose numbers no longer match your study.

Sentence, paragraph or whole document

The unit you rewrite sets a ceiling on what can change.

Sentence level can only reorder and resubstitute inside one sentence. The rhythm across the paragraph is untouched, so this changes the least. See sentence rewriter.

Paragraph level can merge two sentences, split one, move a clause across a boundary. This is where most of the available improvement lives. See paragraph rewriting.

Document level can also vary how sections open and close and strip repetition across paragraphs, which is where generated long-form gives itself away hardest.

What rewriting does not do

It changes the text. It does not change what the text is, and no rewrite makes a claim about authorship true or false. Detection scores describe how writing reads, not how it was made, which is a limit on every tool on both sides of this. See why AI detectors flag human writing.