HomeAI Detector › Sentence-Level Detection

Sentence-Level AI Detection — see which sentences flag, fix only those.

A 62 percent overall AI score on a 2,000-word article is not a fix path. It is a riddle. Which 62 percent? Which paragraphs are doing the damage? Without that detail the only honest move is to rewrite the whole piece, which is exactly what the detector was supposed to save you from. TextSight returns the overall score, then breaks it down per sentence: every line gets its own colour band, its own 0 to 100 score, and a reason explaining which signal triggered the flag. You edit the 6 to 12 sentences that are genuinely AI-shaped, leave the rest alone, and ship the article. That is the difference between a verdict machine and an editing tool, and it is the reason sentence-level highlights are the default scan view on every TextSight plan, including the free 3-scans-a-day tier.

Run a sentence-level scan free See the workflow
6 signal types scored per sentence 5 colour bands per line Free on every tier, including 3 scans/day
The differentiator

One document score is not a fix path.

Most competitors give you one number for the whole document. We give you the number too, then we give you the map. The number tells you something is wrong. The map tells you what to do about it.

What a whole-document score actually tells you

Imagine an editor opens a 2,000-word article and sees "62% AI" from a single-number detector. What does that mean in practice? Maybe 62 percent of sentences read AI. Maybe 62 percent confidence the whole document is AI. Maybe two flagged paragraphs were averaged across the rest. Different detectors mean different things by the same number, and none of them tell the editor where the problem lives. The only honest next step is to open the article and read every line, which is exactly the work the detector was meant to replace.

What sentence-level results add

TextSight scores every sentence on its own. Each line gets a colour band, a 0 to 100 score, and the specific signal that triggered the flag (rhythm flat, vocabulary cluster, polite-assistant pattern, and so on). On the same 2,000-word article the editor now sees that 9 sentences out of 110 are red, 4 are yellow, and the rest are green. The fix path is suddenly obvious: rewrite the 9 red sentences, decide on the 4 yellow ones, leave the 97 green ones alone, rerun the scan, and ship.

The time-savings math

A full rewrite of a 2,000-word draft takes 60 to 90 minutes. Editing 9 flagged sentences in place takes 8 to 12 minutes. That is the entire reason sentence-level highlights exist as a product surface, and it is why we ship them on the free tier rather than gating them behind a paid plan. A detector without per-sentence detail is a verdict machine. A detector with per-sentence detail is an editing tool.

4-step workflow

Paste, scan, review, edit only the flagged sentences.

The whole loop takes a few minutes once the muscle memory is there. The point of sentence-level results is that step four is targeted, not a full rewrite.

1. Paste the text

Open app.textsight.ai and paste up to 5,000 characters on the free tier, 10,000 on Starter, 50,000 on Pro, or 150,000 on Business. The character counter ticks live as you type. No signup is required for your first scan, and there is no credit card request anywhere in the free flow.

2. See the overall score and per-sentence scores together

Click Scan. The classifier runs in about six seconds on short text and around thirty seconds on a 2,000-word article. The result panel returns a single overall 0 to 100 Authenticity Score at the top, then renders the full text below with every sentence colour-banded in place. Hover any sentence to read its individual score.

3. Review the evidence per sentence

Open a flagged line and the reason panel lists which of the six signals fired on that sentence: rhythm flat, vocabulary cluster, paragraph cadence, sentence-length variance, transition cluster, or polite-assistant pattern. Clustered red sentences with consistent signals are real evidence. Isolated yellow lines in a green essay are usually false positives on formal or templated prose, and the colour map makes that distinction visible at a glance.

4. Edit only the flagged sentences

Rewrite the red lines in place, or click the per-line AI Rewriter button to rewrite a single flagged sentence without touching the rest of the document. Rerun the scan to confirm the page is mostly green. The point of the four-step loop is that step four is targeted editing of 6 to 12 sentences, not a full rewrite of the whole article.

Under the hood

Six signal types, scored on every sentence.

Each signal returns a 0 to 100 score for the sentence. The six are weighted and combined into the colour band the editor sees. The full methodology is published; the short version is below.

1. Rhythm flat

Native human writing varies sentence rhythm naturally: a short line, a longer one, a fragment, a question. AI output tends to lock into a narrow rhythm where every sentence lands within a few syllables of the same shape. The rhythm signal compares the sentence against a baseline distribution and flags sentences that sit inside the flat-rhythm cluster characteristic of GPT-4 and Claude.

2. Vocabulary cluster

About eighty words are over-used by current frontier models well above their human baseline frequency: delve, tapestry, navigate, robust, leverage, seamless, transformative, empowers, elevate, and the rest of the shortlist. The vocabulary signal counts matches against the baseline and flags sentences that pack three or more cluster words inside a short line.

3. Paragraph cadence

AI tends to open and close every paragraph the same way: topic sentence, three supporting sentences, summary closer. The cadence signal tracks paragraph shape across the document and flags individual sentences whose position in the paragraph matches the AI template exactly (especially the synthesis closer, which is one of the strongest single tells).

4. Sentence-length variance

Burstiness, in the perplexity literature. Humans land bursts of short and long sentences in sequence; AI smooths the variance out so every sentence falls within a 16-to-22-word band. The variance signal measures the running standard deviation of sentence length in a small window around the line and flags sentences that sit inside a low-variance cluster.

5. Transition cluster

Furthermore, Moreover, In addition, Additionally, Importantly, Notably. AI loves a stacked transition at the start of a paragraph or a sentence. The transition signal counts cluster words at sentence openings and flags lines that begin with one when the surrounding paragraph already opened with another.

6. Polite-assistant pattern

The hedge-and-summarise register the assistant family is trained into: "it is important to note that," "while this approach has merits," "ultimately, the best path forward depends on." The polite-assistant signal flags sentences whose structure matches the register fingerprint, which is the single most consistent tell across model generations.

Free on every tier

Sentence highlights ship on the free plan, not behind a paywall.

Most competitors hide the per-sentence view behind a paid upgrade. We ship it as the default scan view on every plan, including the 3-scans-a-day free tier. The reasoning is straightforward.

What you get on the free tier

Three scans a day, up to 5,000 characters per scan, the full five-band colour map on every sentence, the per-line reason panel, hover-to-score on every line, and access to the per-sentence AI Rewriter on flagged sentences. No credit card, no email-only paywall, no "Pro feature" badge on the colour view.

Why we make the opposite call to competitors

A document-level percentage without per-sentence detail is the wrong product to ship to anyone who actually has to edit the text. It generates an inscrutable number, hands it to the writer, and walks away. The writer either rewrites the whole article from scratch or ignores the verdict, neither of which is the workflow the detector should be enabling. Sentence-level highlights turn the detector into an editing tool, and the editing tool is the actual product. Putting that product behind a paywall would defeat the point.

What changes on paid tiers

Volume cap (10,000 to 150,000 characters per scan), scan frequency (20 a day on Starter, unlimited on Pro and above), file and URL upload, per-sentence PDF and CSV export, white-label exports on Business, REST API access for downstream review tooling, and team seats. The classifier itself, the six signals, the colour bands, the reasons, and the per-line AI Rewriter are identical on every plan.

Plans & pricing

Sentence highlights on every tier.

The classifier, the six signals, the colour bands, and the per-line reasons are identical on every plan. Paid tiers raise the cap and unlock uploads, exports, API, and seats.

Free
$0/forever

 

Sentence-level scans on a single essay or draft, no card.
  • 3 scans / day
  • 5,000 chars per scan
  • Full 5-band sentence highlights
  • Per-line reasons and AI Rewriter
Start free
Starter
$7.49/month

Billed $89.88/year — Save $30

For active writers running sentence-level scans daily.
  • 20 scans / day
  • 10,000 chars per scan
  • Chrome extension
  • Email support
Get Starter
Business
$29.99/month

Billed $359.88/year — Save $120

For agencies and schools running sentence-level review at scale.
  • 150,000 chars per scan
  • REST API (per-sentence JSON)
  • 5 team seats
  • White-label PDF exports
Get Business

Sentence highlights are part of every tier, including Free. Yearly billing saves 25%. View full pricing →

FAQ

Sentence-level questions people actually ask.

What is sentence-level AI detection?
Sentence-level AI detection scores every sentence in a document on its own and shows the result as a colour band on the line itself, instead of returning a single percentage for the whole document. Each sentence gets a 0 to 100 score, a band ranging from Original through AI Generated, and a reason explaining which signal triggered the score. The intent is to make the result actionable: instead of rewriting an entire 2,000-word draft to chase a 62 percent overall score, you rewrite the 6 to 12 sentences that are actually flagged.
How is this different from a normal AI detector score?
Most detectors return one document-level percentage. That number says something is off, but it does not say where the problem is or what to rewrite. TextSight returns the same overall score and then breaks it down per sentence with colour bands, reasons, and one-click AI rewriter access on any flagged line. You stop guessing which paragraphs are doing the damage and start fixing only what needs fixing.
Which six signals are scored per sentence?
Rhythm flat (sentences land within a narrow word-count range), vocabulary cluster (over-use of the AI-favourite shortlist like delve, tapestry, navigate, robust), paragraph cadence (every paragraph opens and closes with the same shape), sentence-length variance (the burstiness humans show is missing), transition cluster (Furthermore and Moreover stacked at paragraph starts), and polite-assistant pattern (the hedge-and-summarise register). Each signal returns a 0 to 100 score for the sentence.
Do free users get sentence-level highlights?
Yes. Sentence-level highlights are the default scan view on every TextSight plan, including the free 3-scans-a-day tier. Most competitors gate this view behind paid plans. We made the opposite call, because a document-level percentage without per-sentence detail is the wrong product to ship to anyone who actually has to edit the text.
How much time does sentence-level editing actually save?
On a 2,000-word article that scores 60 percent AI on a whole-document detector, the typical fix path is somewhere between 6 and 12 flagged sentences out of 80 to 120 total. Rewriting only those flagged lines takes 8 to 12 minutes, against 60 to 90 minutes for a full rewrite. Most TextSight users report cutting revision time roughly in half within their first week of using sentence-level results instead of overall scores.
Can I trust a single yellow sentence in a green essay?
A single yellow or red sentence inside an otherwise green document is almost always a false positive on a formal or templated line, not a verdict on your authorship. The advantage of sentence-level results is that the colour map itself makes the false positive visible: an isolated flag reads very differently from a cluster of red lines in a single paragraph. Read the flagged line, decide if the language is genuinely AI-shaped, and move on if not.
Can I export the per-sentence breakdown?
Yes on Pro and above. Export the per-sentence results as a PDF that preserves the colour bands and the trigger reason for every flagged line, or as a CSV with one row per sentence including the 0 to 100 score and the signal list. Business and Enterprise exports are white-labelled, which is the format SEO agencies and editors use when sharing the breakdown with clients.
Does the AI Rewriter work on a single flagged sentence?
Yes. Click any flagged sentence in the result view and the AI Rewriter can rewrite that one line on its own, without touching the rest of the document. That is the workflow we recommend on borderline results: rewrite only the red sentences, rerun the scan, and ship once the page is mostly green. The same AI rewriter can be run on the whole document at once when you prefer a single pass.
Related

More for the sentence-level editing workflow.

Stop guessing which 62 percent. See which sentences flag.

Free 3 scans a day, no card, full 5-band sentence highlights on every plan. Edit the 6 to 12 lines that need it, leave the rest alone.

Run a sentence-level scan free See pricing
6 signal types per sentence · 5 colour bands per line · Free on every tier