10 Best AI Detectors in 2026: Accuracy, Pricing, Limits, and Who Each One Fits

An AI detector returns a probability, not a verdict. Seven of the ten vendors here say so somewhere in their own documentation, and one of them refuses to print an exact number below 20% because false positives cluster there.

That single fact should change how you shop. The useful question is not “which detector is most accurate”. It is whether the tool will accept the text you need to check, what it costs once your team is on it, and what happens when it is wrong about a real person’s work.

This guide ranks ten AI detectors for US buyers on the things that decide the purchase. Those are minimum usable input length, what the free tier actually allows, published pricing and the cost at ten seats, access model, content-type limits, and how each vendor handles uncertainty. It sits inside the wider SaaS CRM Review coverage of the best AI tools for content creation.

Pricing and plan limits below were verified against each vendor’s own page.

Quick Verdict: Best AI Detector by Use Case

Plan sources: Pangram, GPTZero, Originality.ai, Copyleaks, Scribbr, QuillBot. Also Winston AI, Sapling, Turnitin, Grammarly.

Budget pick: GPTZero Essential at $8.33 per month on annual billing.

Enterprise pick: Copyleaks Pro, because its user seats are already inside the plan price.

Free pick: Scribbr, because nothing here caps how many times a day you can check.

How We Chose and Evaluated the Best AI Detectors

These rankings are built from official pricing pages, vendor help-centre documentation, product and feature pages, and clearly labelled third-party evidence. Every price, plan allowance, and input limit quoted here was verified against the vendor’s own page on 2026-08-21.

Each detector was assessed against the same buyer-focused criteria. Those criteria are minimum usable input length, free-tier capacity, published price and billing basis, cost at team scale, access model, workflow fit, language and content-type coverage, and documented uncertainty.

Greater weight went to the factors that change a purchase or an outcome. Those are whether a tool accepts the length of text you need to check, whether seats are bundled or billed separately, whether an allowance carries over, and whether false-positive handling is published. Popularity, marketing accuracy percentages, and affiliate relationships did not influence the order.

Vendor benchmark results are reported as vendor claims and are never treated as independent proof. Claims that could not be verified from a primary source were left out rather than softened, and the published review methodology explains how that evidence standard is applied.

The Three Problems That Decide Which AI Detector You Need

Most comparison tables rank these tools on an accuracy percentage. That number is the least portable thing about them, because every vendor measures it on its own corpus, against its own choice of models, using its own threshold.

Three other problems decide the purchase, and all three are documented by the vendors themselves.

Problem 1: Your text may be too short for the tool to answer at all

Nine of the ten publish a length below which they either refuse to run or warn that the result is less reliable. Copyleaks publishes neither, and the floors that do exist are not close to each other.

Pangram enforces a minimum length of 50 words and explains the reason plainly: the model needs enough context to make a prediction you can trust.

QuillBot requires a minimum of 80 words to scan, and Winston AI needs 500 characters. Turnitin will not produce a report below 300 words of prose text in a long-form writing format.

A discussion-board post, a cover letter paragraph, or a product description sits under several of those floors at once. If that is the content you screen, the accuracy debate is irrelevant and the floor is the whole decision.

Problem 2: The score is a screening signal, and the vendors say so

Detection models are statistical classifiers trained on the output of the same kinds of systems described in the SaaS CRM Review primer on what generative AI is, which is why their answers arrive as probabilities.

Scribbr states that no AI Detector can provide complete accuracy. QuillBot puts it more bluntly: results are probability estimates, not verdicts.

Grammarly tells its own users that scanned-text percentages may differ from those of other solutions like Turnitin, GPTZero, Copyleaks. It adds that its own writing agents will raise the score on text a human wrote and then asked Grammarly to rewrite.

Turnitin goes furthest. Between 0% and 20% it prints an asterisk instead of a number, because no score or highlights are attributed for AI detection scores above 0% and below the 20% threshold.

A vendor deliberately hiding its own output in the range where it is least reliable is the clearest statement in this category about what these numbers are worth.

For a buyer, the consequence is procedural rather than technical. A detector belongs in a review process that also includes a human read and some form of drafting evidence, and no adverse decision should rest on one percentage.

Problem 3: The headline price is not the price your team pays

Two pricing models sit inside this ranking and they behave differently once more than one person needs access.

Pangram Team, Sapling Enterprise, and Grammarly Pro bill per seat. Copyleaks Pro and Winston Elite bundle seats into a flat plan, so the tenth user costs nothing extra.

That reverses the ranking: the cheapest single-seat detector here is not the cheapest ten-seat detector, and the gap runs to 174 dollars a month.

Credits add a second layer. Originality.ai subscription credits carry a one-month expiry and reset each cycle, and Copyleaks warns that switching plans will override your current plan, including any remaining credits.

Both are ordinary billing mechanics, and both cost money that never appears in a starting-price table.

Best AI Detectors Compared

Products are listed in ranked order. Prices are US list prices for the entry paid plan; the annual column shows the effective monthly rate a vendor quotes for annual billing.

Access and limit sources: Pangram minimum word count, GPTZero benchmark conditions. Also Originality.ai false-positive guidance, Copyleaks plan terms. Also Scribbr, QuillBot, Sapling. Also Winston AI scannable content, Turnitin AI Writing Report, Grammarly AI Detector guide. Wide tables here keep the detector name pinned in the first column and scroll horizontally on narrow screens.

Read the table by access model first, not by price. Turnitin cannot be bought by an individual at all, Scribbr and QuillBot are free tools with per-submission ceilings rather than subscriptions, and Grammarly is a feature you already half-own if your team pays for Grammarly.

Only Pangram, GPTZero, Originality.ai, Copyleaks, Winston, and Sapling compete as standalone purchases.

Language coverage is not the same as language accuracy

Pangram advertises detection in over 20 languages, and Copyleaks advertises AI detection in 30-plus languages.

Turnitin supports three: English, Spanish, and Japanese.

Those numbers describe availability, not validated performance. None of the vendor pages used here publishes per-language accuracy evidence, so a 30-language claim tells you the feature runs, not that it runs equally well in Portuguese and English.

Turnitin’s short list is worth reading the other way round. An institution that restricts its report languages to three is making a narrower promise, and a narrower promise is easier to keep.

If you screen non-English content, treat a broad language count as permission to try rather than as evidence, and pilot on documents whose authorship you already know.

AI-generated, AI-refined, and human are three different findings

The human-versus-AI binary broke as soon as writers started drafting themselves and asking a model to tidy the result. Two detectors here handle that directly.

Scribbr reports four categories rather than two: AI-generated, AI-generated and AI-refined, human-written and AI-refined, and human-written. QuillBot returns a likelihood score with explanations rather than a pass or fail.

Grammarly sits at the awkward end of the same problem. Its own documentation warns that using its writing agents will raise the percentage score, which means a Grammarly user can push their own human draft into a higher AI band by accepting Grammarly’s suggestions.

For anyone setting policy, that is the sentence to circulate. A rule that treats any nonzero AI score as misconduct will catch people who used a grammar tool their employer or school pays for.

The 10 Best AI Detectors in 2026

Each entry below carries the same decision fields in the same order, so a price or a limit sits in the same place every time. Depth varies with rank and with how much the evidence supports.

1. Pangram: Best for risk-sensitive review of long-form prose

Best for: editors, admissions reviewers, and integrity teams who care more about the cost of a wrong call than about the monthly price.

Avoid if: you mostly screen text under 50 words, or you need ten seats on a tight budget.

Starting price: Free plan at 2,000 words per day; Individual at $20 per month.

Practical tier: Individual at $20 per month for up to 300,000 words is the first plan that supports steady review work.

Free plan: 2,000 words per day, three image detection scans daily, browser extension and Google Docs integration included.

First limit that bites: the 50-word floor, then the per-seat Team price once a second reviewer needs access.

Better than GPTZero: Pangram publishes its minimum length as a design decision with a stated reason, rather than as a dashboard note.

Worse than Copyleaks: Team charges $20 for each seat per month with a two-seat minimum, against a Copyleaks Pro plan that bundles 25 seats, so ten reviewers cost 200 dollars a month.

Setup difficulty: Low. Browser extension, Google Docs, and web app cover most review work without admin involvement.

Hidden costs: seat count on Team, and Developer API usage billed separately in prepaid tiers from $25 upward.

Evidence status: pricing, plan allowances, and the word floor come from Pangram’s own pricing page and its minimum-word-count explainer. No independent benchmark in the sources used here covers Pangram against the other nine tools on one corpus.

What separates Pangram from the rest of this list is not a number it publishes but a behaviour it refuses. Below 50 words it will not give you an answer at all.

That is unusual and it is the right instinct. Every other vendor here handles short text by returning a less reliable score with a caveat attached, which puts the burden of remembering the caveat on the reviewer at exactly the moment they are least likely to.

The free tier is also genuinely usable rather than a demo. At 2,000 words per day, a teacher spot-checking two or three essays never has to pay, and the paid step-up is a straightforward jump to 300,000 words a month.

Where it gets expensive is scale. Pangram is the only tool in the top four that charges per seat with no bundled team allocation, so an eight-person editorial desk pays more here than at Copyleaks, Winston, or Originality.ai.

Both columns above draw on Pangram’s official plan and documentation pages.

Verdict: the detector to put in front of a reviewer whose decision affects someone’s grade, byline, or job, provided the text clears 50 words and the seat count stays small.

2. GPTZero: Best for education teams on a low paid entry price

Best for: teachers, academic reviewers, and small departments that want a real paid allowance without a departmental budget line.

Avoid if: you need independent proof of accuracy before you can defend the tool to a committee.

Starting price: Essential at $14.99 per month billed monthly.

Practical tier: Essential at $8.33 per month billed annually, with 150,000 words per month, which is the cheapest serious allowance in this ranking.

Free plan: free document scanning up to 10,000 characters at a time.

First limit that bites: the per-scan character ceiling. Essential and Premium allow 50,000 characters per scan; only Professional raises that to 150,000.

Better than Scribbr: a paid plan with a monthly word budget instead of a cap of 1,200 words on every submission.

Worse than Pangram: its accuracy evidence is self-published, so it carries less weight in a formal appeal.

Setup difficulty: Low. Web scans need no IT involvement, and the free tier works before any purchase.

Hidden costs: the jump to Professional at $24.99 per month on annual billing if long documents keep hitting the 50,000 character scan ceiling.

Evidence status: prices and word allowances come from GPTZero’s own pricing article; the benchmark figures come from GPTZero’s own benchmarking post and stay attributed to GPTZero throughout.

GPTZero publishes more about its own testing than anyone else here, and that cuts both ways. Its published benchmark covers four writing domains, academic paper reviews, creative writing, essays, and product reviews, and names the models it tested against, including GPT-5.2, Gemini 3 Pro, Claude Sonnet 4.5, and Grok 4 Fast.

Transparency about method is worth something. It is still the vendor marking its own work, and a benchmark run by the company selling the detector cannot settle a dispute with a student who says the flag is wrong.

The pricing is the stronger argument. At $8.33 a month for Essential on annual billing, a department can put a real allowance in front of every teacher, and 150,000 words a month covers a heavy marking period.

Watch the scan ceiling rather than the monthly total. As an example, a dissertation chapter of 60,000 characters does not fit in one Essential scan, and splitting long documents is exactly the behaviour that pushes results toward the short-text unreliability every vendor here warns about.

Both columns above draw on GPTZero’s official plan and documentation pages.

Verdict: the sensible default for a school or department buying detection for many people on a small budget, as long as nobody presents its published accuracy figures as neutral evidence.

3. Originality.ai: Best for publishers and content operations

Best for: publishers, SEO agencies, and editorial teams screening a recurring volume of commissioned copy.

Avoid if: you scan in short bursts and would rather not lose an unused monthly allowance.

Starting price: Pro at $14.95 per month billed monthly.

Practical tier: Pro at $12.95 per month on annual billing with 2,000 credits, where one credit equals 100 words, which works out to roughly 200,000 words a month.

Free plan: none listed on the pricing page.

First limit that bites: credit expiry. Subscription credits carry a one-month expiry and reset each cycle, so a quiet month is money gone.

Better than QuillBot: file upload, full site scans, team management, and shareable reports sit in one workflow rather than in a writing app.

Worse than Copyleaks: API access is gated to Enterprise at $136.58 per month on annual billing, where Copyleaks exposes API and role controls through its enterprise track.

Setup difficulty: Medium. Site scans and team management need someone to own the account and the tagging convention.

Hidden costs: Enterprise is the only route to API access, at $136.58 per month on annual billing, and Pro keeps only 30 days of scan history.

Evidence status: plan prices, credit mechanics, and feature gating come from Originality.ai’s pricing page; the 100-word recommendation comes from its own false-positive help article.

Originality.ai is the only tool here built around the shape of a content operation rather than a document. Full site scans, tags, team management, and downloadable reports are the reason to buy it, and AI detection is one component of a verification stack that also covers plagiarism, readability, grammar, and fact checking.

The credit model rewards steady volume and punishes irregular use. Two thousand credits a month is generous for a team commissioning weekly, and worthless to an editor who checks four articles in March and forty in April, because subscription credits carry a one-month expiry.

Separately purchased credits behave differently and expire two years after purchase if unused, which is the buffer to use for uneven workloads.

The false-positive guidance is the most operationally useful thing the company publishes. It recommends scanning at least 100 words and warns that formulaic content often gets flagged as high-probability AI. It also suggests reviewing three to five works from the same author before drawing a conclusion.

That last point is a workflow instruction, not a disclaimer. A publisher screening a new freelancer should be checking a body of their work, not one submission, and a tool that says so is easier to defend than one that ships a single percentage.

Both columns above draw on Originality.ai’s official plan and documentation pages.

Verdict: the strongest fit for a team that screens content every week and wants site-level coverage, provided the monthly credit expiry matches how the work actually arrives.

4. Copyleaks: Best for multilingual and multi-seat organisations

Best for: organisations reviewing content in several languages, or any team that needs more than five people on the same detector.

Avoid if: you expect to move between plans, because unused credits do not survive the switch.

Starting price: Personal at $16.99 per month billed monthly.

Practical tier: Pro at $74.99 per month on annual billing, with 1,000 unified credits and 25 user seats.

Free plan: the pricing page lists no free tier for Copyleaks.

First limit that bites: the credit conversion. Personal’s 100 monthly credits buy roughly 25,000 words or 100 images, which a single long report can consume.

Better than Winston AI: 30-plus AI-detection languages and 100-plus plagiarism languages, against Winston’s documented weakness on translated content.

Worse than GPTZero: Personal at $13.99 against GPTZero Essential at $8.33 makes the annual entry rate about two thirds higher, and the Personal word allowance is far smaller.

Setup difficulty: Medium on Pro and High on Education or Enterprise, where role-based access and data-hosting choices need administrator time.

Hidden costs: extra credits bought outside the plan, and the credits forfeited whenever a plan changes.

Evidence status: prices, credit conversions, seat counts, language claims, and the plan-switching rule all come from the Copyleaks pricing page.

Copyleaks is the only tool in the top four where the tenth user is free. Pro includes 25 user seats inside its $74.99 annual rate, so a ten-person integrity team pays a little over a third of what the same team pays elsewhere.

The comparison is Pangram Team at $20 for each seat per month.

The credit mechanics are where buyers get caught. Personal buys 100 unified credits a month, converting to about 25,000 words or 100 images, so a single long report plus a handful of image checks makes a real dent.

The plan-switching rule deserves a calendar reminder rather than a footnote. Copyleaks states that plans do not stack and that switching overrides the current plan including any remaining credits, so an upgrade timed a week into a billing cycle throws away whatever is left.

For multilingual work, treat the language count as scope rather than as a performance guarantee, and pilot each language you actually care about against documents whose authorship you already know.

Both columns above draw on Copyleaks’s official plan and documentation pages.

Verdict: the pick when seat count or language coverage drives the decision, and the one plan here where the upgrade timing is worth planning around.

5. Scribbr AI Detector: Best free checks for students and individual writers

Best for: students and individual writers who need repeated zero-cost checks on the same document.

Avoid if: your documents run past 1,200 words, or you need an audit trail.

Starting price: free.

Practical tier: the free detector, with the premium AI Detector included free alongside a premium plagiarism check from $19.95 for a document up to 7,499 words.

Free plan: unlimited free AI checks, up to 1,200 words per submission.

First limit that bites: the submission cap of 1,200 words, which forces a dissertation chapter into several separate scans.

Better than QuillBot: no daily scan limit at all, so a student can check the same paragraph twenty times while editing.

Worse than Originality.ai: no team management, no site scanning, and no exportable record of what was checked.

Setup difficulty: Low. Open the page, paste, and scan.

Hidden costs: none on the free detector; the premium tier is priced per document rather than per month.

Evidence status: the free allowance, language list, category labels, and accuracy caveat come from the Scribbr AI detector page; the per-document pricing comes from its plagiarism-checker page.

Scribbr’s pricing model is the one most often misread. There is no AI-detector subscription here: the free checker is genuinely free and unlimited, and the premium detector arrives bundled with a per-document plagiarism check rather than as a recurring charge.

That suits the actual buying pattern of a student, who needs a plagiarism report twice in a degree and a quick AI check twenty times a term. Paying $19.95 for a premium plagiarism check once at submission beats a subscription that sits idle for eleven months.

The four-category output is the other reason it earns a place. Separating AI-generated, AI-refined, and human-written text matches how people actually write in 2026, and it gives a student something more useful than a single percentage to reason about.

The ceiling of 1,200 words is the trade. Longer work has to be split, and splitting pushes each chunk toward the short-text range where Scribbr’s own page says results are less reliable.

Both columns above draw on Scribbr’s official plan and documentation pages.

Verdict: the right free tool for an individual writer checking their own work, and the wrong one for anyone who needs a record of what was checked and when.

6. QuillBot AI Detector: Best free detection inside a writing suite

Best for: students, editors, and existing QuillBot users who want detection next to the paraphrasing and grammar tools they already open.

Avoid if: you need more than six checks in a day without paying.

Starting price: free.

Practical tier: Premium, which removes the detector’s word limit and daily scan cap. No dollar figure for Premium is quoted in this guide, because none was verified against a QuillBot pricing page for this edition.

Free plan: up to 1,200 words per scan and up to six scans per day.

First limit that bites: the six-scan daily cap, which a single editing session can exhaust.

Better than Sapling: 1,200 words per free scan against Sapling’s 2,000 characters, which is roughly three times the free capacity.

Worse than Scribbr: the daily scan cap, where Scribbr imposes none.

Setup difficulty: Low. Browser-based, inside a suite most target users already have.

Hidden costs: none visible on the free tier; confirm the Premium price at checkout before budgeting.

Evidence status: the 80-word minimum, scan limits, reliability guidance, and probability framing all come from the QuillBot AI detector page. The paid price is omitted because this edition carries no verified QuillBot pricing source.

QuillBot writes better guidance than most vendors sell. Its detector page states that longer texts of 300 words or more produce more reliable scores than short inputs. It adds that heavily paraphrased or lightly AI-edited content is harder for any checker to detect, and that formulaic writing such as academic definitions and legal copy can score higher than expected.

Naming legal copy and academic definitions as false-positive risks is unusually specific, and it is the sentence a compliance reviewer should read before screening contract language.

There is an obvious tension in the product itself. QuillBot sells a paraphraser and a detector in the same suite, and the detector’s own page says paraphrased content is harder to detect, which is a candid thing for a vendor to publish about its neighbours on the toolbar.

For readers who want to focus on rewriting rather than detection, our AI humanizer tools guide compares dedicated options for making AI-generated or machine-like text sound more natural.

The free ceiling is generous per scan and tight per day. Six scans covers a student revising one essay and runs out fast for an editor working through a batch.

Both columns above draw on QuillBot’s official plan and documentation pages.

Verdict: the better of the two free detectors for anyone already inside QuillBot, provided six checks a day covers the workload.

7. Winston AI: Best for shareable reports and multi-format review

Best for: publishers and review teams that need a PDF someone else can read, plus image, deepfake, and OCR checks in one place.

Avoid if: you screen source code, social posts, or translated material.

Starting price: Essential at $18 per month billed monthly.

Practical tier: Essential at $10 per month on annual billing, billed as $120 per year, with 100,000 credits a month. Elite at $26 per month on annual billing adds unlimited team members.

Free plan: 2,000 credits on a 14 day trial rather than a standing free tier.

First limit that bites: the 500-character floor, and then the five-member ceiling on Advanced if the team grows.

Better than Sapling: shareable PDF reports, OCR, plagiarism, and AI image and deepfake detection are bundled rather than sold as separate products.

Worse than Copyleaks: documented weakness on translated content, where Copyleaks builds its case on breadth of language support.

Setup difficulty: Low to Medium. Web scans and document uploads are immediate; website certification and API work need someone technical.

Hidden costs: the Advanced to Elite step if more than five people need accounts, though Elite is still only $26 per month on annual billing.

Evidence status: plan prices, credits, and team limits come from the Winston AI pricing page; the input floor and unsuitable content types come from its help-centre article on scannable content.

Winston publishes the clearest list in this category of what it cannot do well. Its help centre requires at least 500 characters, recommends 300 words or more, and marks social posts, bullet lists, translated content, heavily edited AI drafts, and source code as weak or unsuitable.

A vendor that tells you which content to keep away from its product is doing you a favour, and that list happens to describe a large share of what content teams actually publish.

The pricing is the quiet advantage. Elite at $26 per month on annual billing covers unlimited team members, which makes Winston the cheapest way in this ranking to put ten or fifty people on a detector.

Where it earns its place beyond price is format coverage. OCR, image and deepfake detection, plagiarism, and exportable PDF reports mean a review team can handle a submitted screenshot, a scanned page, and a text file in one tool instead of three.

Both columns above draw on Winston AI’s official plan and documentation pages.

Verdict: the pick when a review has to produce a document someone else will read, and the one to skip if translated or list-heavy content dominates your queue.

8. Sapling AI Detector: Best for developers embedding detection

Best for: developers and operations teams putting detection inside their own product or moderation queue.

Avoid if: you want a free web tool for real documents, because 2,000 characters is roughly 400 words.

Starting price: free web detector; Pro at $25 per month billed monthly.

Practical tier: Pro at $12 per month on an annual subscription, which unlocks longer detector queries.

Enterprise tier: Enterprise starts at ten seats and $15 per seat per month.

Free plan: 2,000 characters per query on the web detector.

First limit that bites: the free 2,000-character ceiling, then the 10-seat Enterprise floor if you need admin controls.

Better than Winston AI: detection can sit inside a product rather than a dashboard.

The documented API bills usage from a $5 minimum.

Worse than Pangram: no published hard minimum, only a warning that shorter, more general, more essay-like text raises false-positive risk.

Setup difficulty: Low for the web tool, Medium to High for API integration.

Hidden costs: API usage billed separately from the subscription, and the 10-seat Enterprise minimum.

Evidence status: plan prices and seat minimums come from the Sapling pricing page; character limits, false-positive guidance, and model coverage come from its AI detector page.

Sapling is the developer option in this list, and its most useful published detail is a limitation. Its own page states that the shorter the text is, the more general it is, and the more essay-like it is, the more likely it is to result in a false positive.

Read that carefully in an academic context. A short, general, essay-like piece of writing is a description of a student essay, which is the single most common thing people push through AI detectors.

The paid ceiling is the real differentiator. Free queries truncate at 2,000 characters while paid scans accept up to 100,000, a fifty-fold jump that turns a demo into something you can run a document through.

Code is explicitly a work in progress. Sapling says it tries to avoid predictions for code blocks and that improved support for AI-generated code remains in development, which is a more honest position than a confident percentage on a pull request.

Both columns above draw on Sapling’s official plan and documentation pages.

Verdict: the one to shortlist if detection has to run inside something you are building, and the wrong choice as a free desktop checker.

9. Turnitin AI Writing Detection: Best for institutions already licensed

Best for: universities and schools already paying for Turnitin or iThenticate that want AI detection inside the workflow instructors already use.

Avoid if: you are an individual. There is no consumer route to this product.

Starting price: not published. Pricing comes from an account manager.

Practical tier: the license add-on, which an institution’s Turnitin administrator arranges with their account manager.

Free plan: none.

First limit that bites: the 300-word prose floor, followed by the three supported report languages.

Better than every self-serve tool here: it reports inside the submission workflow an institution already runs, so no separate process is needed.

Worse than Scribbr: a student cannot use it to pre-check their own work, at any price.

Setup difficulty: High, in procurement terms rather than technical ones. Turnitin states that its technical support team cannot enable the feature or modify license agreements.

Hidden costs: the whole price is a negotiation, so budget from a quote rather than from any figure published elsewhere.

Evidence status: the license mechanics come from Turnitin’s help centre; the word range, file requirements, languages, and asterisk threshold come from its AI Writing Report guide.

Turnitin belongs in this ranking because of where it sits, not because a buyer can choose it. An instructor cannot switch it on, and neither can Turnitin’s own support team; activation runs through the institution’s administrator and account manager.

That access model has a consequence students ask about constantly. There is no way to run your paper through the same detector your university uses before you submit, so any self-check is a different model producing a different number.

The report requirements are strict and worth circulating to faculty. Reports need 300 to 30,000 words of long-form prose, in a .docx, .pdf, .txt, or .rtf file under 100 MB, in English, Spanish, or Japanese.

Both columns above draw on Turnitin’s official plan and documentation pages.

Verdict: the default for an institution already inside the Turnitin ecosystem, and effectively unavailable to everyone else.

10. Grammarly AI Detector: Best detection inside an existing writing workflow

Best for: teams and schools already paying for Grammarly that want a check without adopting a second tool.

Avoid if: you want a standalone detector, or your writers use Grammarly’s rewriting agents.

Starting price: included with paid Grammarly plans; Pro is $30 billed monthly.

Practical tier: Grammarly Pro at $12 per member per month billed annually, which is also the per-seat cost for a team.

Free plan: Grammarly has one, but the detector is not part of it.

First limit that bites: Grammarly’s own rewrites, which raise the AI score on text a human wrote.

Better than Sapling: it runs where writing already happens, in Google Docs and the Mac and Windows desktop clients.

Worse than Pangram: no published minimum length, only a note that shorter passages are harder to measure.

Setup difficulty: Low where Grammarly is already deployed, since the detector arrives with the existing browser extension and desktop clients.

Hidden costs: none beyond the plan, though the detector alone rarely justifies buying Grammarly.

Evidence status: Pro pricing comes from Grammarly’s Pro page; detector availability, surfaces, score meaning, and the rewrite warning come from its AI Detector user guide.

Grammarly’s detector is a feature of a writing suite rather than a product you would buy on its own. The user guide lists it across Pro, Plus, Business, and Education plans, in Google Docs and the Mac and Windows desktop clients.

The company is unusually direct about what the number means. The score represents the percentage of scanned text likely to be AI-generated, and Grammarly says its model is tuned to minimise false positives because wrongly flagging human writing is the more damaging error.

Then comes the self-inflicted problem. Grammarly warns that using its own writing agents raises the percentage score, because the rewrites come from its LLM, so a writer who accepts Grammarly’s suggestions on their own draft moves their own work up the AI scale.

Any organisation that pays for Grammarly and also polices AI use needs to reconcile those two facts in policy before an accusation lands on someone’s desk.

Both columns above draw on the Grammarly Pro plan page and the Grammarly AI Detector guide. The cross-detector comparison rests on the Turnitin AI Writing Report guide.

Verdict: worth switching on if your team already pays for Grammarly, and not a reason to start paying for it.

AI Detector Accuracy: Why One Score Is Not Proof

Every detector in this ranking outputs a percentage. Almost nothing else about those percentages is comparable.

Two detectors can disagree about the same document, and neither is broken

Different models, trained on different corpora, with different thresholds, produce different percentages for identical text. Output from a general assistant such as the one covered in the SaaS CRM Review ChatGPT review will not score the same way across two detectors.

Grammarly says so in its own help documentation, naming Turnitin, GPTZero, and Copyleaks as tools whose scores will differ from its own.

Community threads describing four detectors returning four different results for one unchanged essay are reporting expected behaviour, not a scandal. Those posts are anecdotes rather than evidence, and they are useful only for the question they raise: what do you do when the tools disagree.

The wrong answer is to average the scores. As an example, a 60 from one product and a 20 from another are not two measurements of the same quantity, so the mean of them measures nothing.

The right answer is to treat agreement as weak corroboration and disagreement as a reason to stop and look at the writing itself.

Turnitin’s asterisk is the most honest thing in the category

Turnitin prints an asterisk instead of a number for any AI score above 0% and below 20%, and states the reason: avoiding potential false positives.

That is a vendor deliberately withholding its own output where it trusts it least. It is also the single best argument against treating any low percentage from any tool as meaningful, because the only company here that publishes an uncertainty threshold put it at 20%.

Apply the principle even where the vendor does not. A score of 12%, as an example, is closer to noise than to a finding from any detector in this list.

Edited and paraphrased text is a different problem from raw AI output

A clean paste from a model and a human draft that was tidied by a model are not the same detection task, and vendor accuracy claims almost always describe the first one.

QuillBot states that heavily paraphrased or lightly AI-edited content is harder for any AI checker to detect. Winston lists heavily edited AI drafts and translated content among the material it handles poorly.

Originality.ai warns that formulaic content often gets flagged as high-probability AI regardless of who wrote it.

Put those together and a pattern appears that matters more than any accuracy percentage. Detection gets harder exactly as the human contribution increases, and false positives get more likely exactly as the writing gets more formulaic.

The people most exposed are therefore the ones writing structured, conventional prose: non-native English writers trained on formal templates, legal and compliance teams, and students taught to follow an essay scaffold.

The evidence ladder: what a score is allowed to do

A detector score is the first rung of a review, not the last. Each rung below adds something the rung beneath it cannot supply.

1. Detector output. A probability with a documented minimum length and a documented uncertainty band. It can start a review. It cannot end one.
2. Human reading. Does the writing match this author’s other work, the assignment, the brief, the subject knowledge on display?
3. Process evidence. Drafts, version history, revision timestamps, notes, source material. This is the only layer that speaks to authorship directly.
4. Conversation. Ask the author about their argument, their sources, and their choices.
5. Decision. Taken on the accumulated picture, and recorded with the reasoning.

The ladder is also a procurement argument. If your organisation cannot supply rungs two through five, buying a better detector will not fix the process, and a cheaper detector will not make it worse.

Pricing, Limits, and Minimum Text Lengths

Three numbers decide the real cost of a detector: the published price, the number of people it has to cover, and the amount of text it will accept in one go. Vendors publish the first one prominently and the other two in help articles.

Monthly and annual prices are not close together

Source, published rates: Pangram, GPTZero, Originality.ai, Copyleaks, Winston AI, Sapling. Also Grammarly. Scribbr, QuillBot and Turnitin are excluded because they are not sold as a monthly detector subscription. GPTZero renders its plan figures in the browser, so the Essential values were read from its own published plan comparison on the same date.

GPTZero’s pricing page renders its plan figures in the browser, so the Essential values above were read from GPTZero’s own published plan comparison on the same date.

Annual billing roughly halves the price at GPTZero, Winston, Sapling, and Grammarly, and barely moves it at Originality.ai and Copyleaks.

That gap is worth a moment before committing to twelve months. A saving of roughly 44% justifies the lock-in far more than one of roughly 13% does.

What ten people actually cost

The starting price is a one-seat number, and detection is rarely a one-person job. Seat models diverge sharply once a team is involved.

Plan sources: Winston AI, Copyleaks, Grammarly, Sapling, Pangram.

Read that ordering next to the single-seat table and the reversal is complete. Winston, seventh in this ranking, is the cheapest tool here for a ten-person team, and Pangram, first in this ranking, is the most expensive.

That is not an argument for buying on price. It is an argument for pricing your actual headcount before you shortlist, because the per-seat products punish exactly the organisations most likely to need detection.

What “free” actually buys

Five detectors here offer something free, and the five allowances are measured in five different units. Converting them into one score would invent precision that does not exist, so the units stay separate.

Plan sources: Pangram, Scribbr, QuillBot, Sapling, GPTZero.

Scribbr is the only one with no daily ceiling at all, which makes it the free tool for someone editing the same document repeatedly. Pangram is the most generous per day for someone checking several different documents.

Sapling’s free tier is a demonstration rather than a working allowance. At roughly 400 words it clears the minimums but leaves no room for a real document, which tells you it is there to show the product rather than to do a job.

Minimum input: hard gates and soft warnings are different things

Some of these tools refuse to run below a threshold. Others run and quietly return something less reliable.

Confusing the two is how a reviewer ends up acting on a score the vendor never intended them to trust.

Limit sources: Pangram, GPTZero, Originality.ai, Copyleaks, Scribbr, QuillBot. Also Winston AI, Sapling, Turnitin, Grammarly.

Match that table against your own content before anything else in this guide. A team screening short product descriptions can eliminate Winston and Turnitin immediately.

A school screening essays of 1,500 words, for example, can ignore the column entirely.

Where credits expire or disappear

Two of the credit-based tools carry mechanics that cost money without appearing in any price comparison.

Originality.ai subscription credits expire after one month and reset each cycle, so an editorial team with an uneven commissioning calendar buys 2,000 credits every month and uses them in bursts.

Credits bought separately behave better and expire two years after purchase if unused, which makes them the right instrument for lumpy workloads.

Copyleaks forfeits remaining credits when a plan changes, because its plans do not stack and a switch overrides the current plan. An upgrade made mid-cycle therefore costs the unused balance on top of the new plan price.

Neither is hidden, and neither is unusual. Both are worth a note in the renewal calendar, because the fix in each case is timing rather than negotiation.

Feature Gate Comparison

Detection is bundled differently at every vendor, and the bundle is often the real purchase. Rows are products; a gate is named where a plan restricts it.

Feature sources: Pangram, GPTZero, Originality.ai, Copyleaks, Scribbr, QuillBot. Also Winston AI, Sapling, Turnitin, Grammarly.

Image and deepfake columns matter more than they used to, because the same teams screening text now receive assets from the best AI image generators.

Two things fall out of that grid. Winston is the only tool that puts plagiarism, image and deepfake detection, OCR, API, and PDF reports inside an Essential plan at $10 per month on annual billing.

Sapling is the only one that offers essentially nothing except detection and an API, which is precisely what a developer wants.

The gate to watch is API access. Originality.ai reserves it for Enterprise at $136.58 per month on annual billing.

Sapling sells API access usage-based from a $5 minimum, a difference of two orders of magnitude for teams whose only requirement is programmatic access.

Setup and Workflow Difficulty

Nothing here needs a migration project, but the effort to get a whole team using one consistently varies a lot.

Workflow sources: Pangram, GPTZero, Originality.ai, Copyleaks, Scribbr, QuillBot. Also Winston AI, Sapling, Turnitin, Grammarly. Setup ratings are an editorial assessment of those documented workflows.

The pattern is that difficulty tracks governance, not technology. The tools that are hardest to set up are the ones that give an organisation seat control, audit trails, and LMS integration, and those are exactly the features that make a detector defensible when a decision is challenged.

Which AI Detector Should You Choose?

Work through these five steps in order. Each one eliminates products, which is faster than comparing ten tools on ten dimensions.

Step one: measure your shortest routine document. Under 300 words Turnitin will not produce a report at all, and Winston falls below its own recommended length.

Under 80 words QuillBot refuses the scan, and under 50 words Pangram refuses too. Below that, the tools with no published gate will still return a score their own documentation tells you not to trust, which is not the same as an answer.

Step two: count the people who need access. One or two makes GPTZero the cheapest credible option. Five or more makes Winston AI Elite the cheapest option here whatever its rank, and past seven people Copyleaks Pro undercuts every per-seat plan too.

Step three: decide whether you are buying detection or a verification stack. If you also need plagiarism, image checks, OCR, or exportable reports, Winston, Copyleaks, and Originality.ai bundle them. Sapling and GPTZero do not, and cost less for that reason.

Step four: check the access model before the feature list. Turnitin cannot be bought individually. Grammarly’s detector only pays off if the suite is wanted anyway. Scribbr and QuillBot are free tools, not subscriptions.

Step five: write down what happens when the score is wrong. If a flag can affect a grade, a contract, or a job, put the evidence ladder from the accuracy section in place before the tool arrives. Weight false-positive handling over headline accuracy.

How each ranking reason maps to a buyer cohort

Every pick above carries one ranking reason and one cohort it serves, and the two travel together. Pangram earns its position on documented false-positive control for the risk-sensitive review cohort, Winston AI on bundled seats for the multi-person cohort, and Sapling on its documented API for the developer cohort.

The disqualifier matters as much as the ranking reason. If your shortest routine document falls under a published plan gate, that product leaves your shortlist whatever its rank. The vendor’s own official documentation says the workflow will not return a usable result at that length.

So read the ranking as a set of conditional recommendations rather than a league table. The cohort decides the pick, the plan gate decides whether the pick is even available, and the workflow decides whether anyone will keep using it after month two.

Content types where detection does not work well

Some material is a poor fit for every tool here, and the vendors say so.

Common mistakes buyers make with AI detectors

Budgeting from the starting price. The single-seat number and the ten-seat number rank the products differently, and the difference between the cheapest and dearest ten-seat plan here is 174 dollars a month.

Treating a percentage as a measurement. Detectors are classifiers with thresholds, not instruments. Averaging two vendors’ scores produces a number with no meaning.

Buying before checking the floor. A tool that will not accept your typical document is not a cheaper option, it is a non-option, and the floors are published in help articles rather than on pricing pages.

Ignoring credit expiry. A monthly allowance that resets is a use-it-or-lose-it budget, and an upgrade timed mid-cycle at Copyleaks costs the unused balance.

Assuming a language count means language performance. Thirty languages supported is a scope statement, and none of the vendors here publishes per-language accuracy evidence.

Screening your own AI-assisted writing with a tool from the same suite. Grammarly raises the score on text its own agents rewrote, which produces confusing results for teams that use both features.

Deploying the tool before the process. If nobody has decided what happens at example scores of 15%, 45%, and 90%, the detector will make that decision by default, and it is the worst-placed participant to make it.

When not to use an AI detector at all

There are cases where the right answer is to skip detection rather than to choose better.

Skip it when the content sits below every published floor, because no product in this ranking will return a prediction it stands behind. Skip it for code, tables, bullet lists, poetry, and scripts, where the documentation is explicit.

Skip it when the decision is adverse and you have no second and third rung of the evidence ladder, because a single probability is not a basis for an accusation and none of these vendors claims it is.

Skip it when the text came from a support or sales assistant your own organisation deployed, since tools drawn from the best AI chatbots are meant to write that copy.

Skip it when the underlying problem is a policy vacuum. If your organisation has not written down what AI assistance is permitted, a detector will measure something nobody has defined.

Final Verdict

There is no single winner here, because the products are not competing for the same buyer. What there is instead is a clear answer for each of the six situations that account for most of the demand.

For review work where a wrong call costs someone something, and the text runs past 50 words, the shortlist starts with Pangram. It is the only tool here that refuses to answer rather than answering badly, and that instinct is worth more than a percentage point of claimed accuracy, so budget carefully around its per-seat pricing.

For a school or department putting detection in front of many people on a small budget, GPTZero Essential at $8.33 per month on annual billing is the sensible default. The condition is that nobody presents its self-published benchmarks as neutral evidence in a dispute.

For a publishing or content operation screening a recurring volume, Originality.ai is the fit, because site scans, tags, and team management are the actual purchase and detection is one part of it. Match the monthly credit expiry to your commissioning calendar before signing.

For any team of five or more the ranking inverts. Winston AI Elite is $26 per month on annual billing with unlimited members.

Copyleaks Pro is $74.99 per month on annual billing with 25 seats included. Winston if you need reports, OCR, and image checks; Copyleaks if language coverage and seat administration matter more.

For a developer embedding detection, Sapling is the only one here designed for that, with a usage-based API and 100,000-character paid queries.

For students, Scribbr is the free tool to use, with no account and no daily cap. And for anyone already inside Turnitin or already paying for Grammarly, the answer is to switch on what you have rather than buy something new.

The rule that applies to all ten: buy the detector that fits your text length, your headcount, and your process, then treat every number it produces as the first line of a review rather than the last word on it.

Frequently Asked Questions

Seven questions come up again and again once the shortlist is set, and each one turns on evidence no vendor makes public.

Which AI detector is the most accurate in 2026?

No source used for this guide supports a single accuracy ranking across all ten tools. Every published accuracy figure here comes from the vendor selling the product, measured on its own corpus against its own choice of models, and no independent benchmark in the evidence used covers all ten under one protocol.

Choose on input length, seat cost, access model, and false-positive handling, which are verifiable, rather than on an accuracy percentage, which is not comparable between vendors.

Which AI detector has the lowest false-positive rate?

None of these vendors publishes an independently verified false-positive rate, so the honest comparison is how each one handles the risk. Turnitin suppresses exact scores below its 20% threshold specifically to avoid them.

Grammarly states its model is tuned to minimise them, Pangram refuses to predict below 50 words, and Originality.ai publishes guidance on the content types most likely to be wrongly flagged.

Those four disclosures are the strongest available signal, and they are disclosures about design rather than measurements of outcome.

Can Turnitin detect AI writing, and can a student check their own paper with it first?

Turnitin does produce an AI Writing Report, but only for institutions that have added the license, and only for 300 to 30,000 words of long-form prose in English, Spanish, or Japanese. There is no individual purchase route, and instructors cannot enable the feature themselves, so a student cannot run their own paper through the same detector before submitting.

Any self-check uses a different model and will return a different number, which is expected rather than evidence of a problem.

What is the best free AI detector?

Scribbr for repeated checks of the same document, because it imposes no daily cap, only a 1,200-word ceiling per submission. QuillBot if you want explanations alongside the score and six scans a day is enough.

Pangram’s 2,000 words per day suits someone checking several different documents rather than one document repeatedly, and it is the most generous daily allowance among the free tiers here.

Do AI detectors still work after AI text is paraphrased or edited?

Less well, and the vendors say so rather than hiding it. QuillBot states that heavily paraphrased or lightly AI-edited content is harder for any AI checker to detect, and Winston lists heavily edited AI drafts among the material it handles poorly.

Treat a vendor’s headline accuracy claim as a statement about clean, unedited model output, because that is the condition those benchmarks describe, and expect detection confidence to fall as the human contribution rises.

Do AI detectors work in languages other than English?

Availability is broad and evidence is thin. Pangram advertises over 20 languages and Copyleaks advertises 30-plus for AI detection.

Turnitin limits its reports to English, Spanish, and Japanese.

None of the vendor pages used here publishes per-language accuracy evidence, so treat a language count as permission to try rather than as proof of performance, and pilot on documents whose authorship you already know before relying on the result.

Can a school or employer act on an AI detector score alone?

Nothing in the evidence used for this guide supports that. The vendors themselves describe their outputs as probability estimates, percentages of scanned text, or scores that differ between products, and the one company that publishes an uncertainty threshold withholds its own number below 20%.

A defensible process uses the score to open a review, then adds a human reading, drafting and version evidence, and a conversation with the author before any decision is recorded.

Choose the detector that fits your own risk tolerance and workflow, then trial or subscribe only after reviewing its input limits, access model, pricing, and false-positive caveats.

About the author

Macedona

Macedona is the founder and lead reviewer at SaaS CRM Review, where he has published 175+ in-depth reviews, pricing guides, and comparisons of CRM and SaaS tools. Each review is based on hands-on testing or verified documentation, and every article states clearly which method was used. Pricing and features are checked against official vendor sources, with the verification date noted in the article. Macedona follows a published review methodology and editorial policy. SaaS CRM Review earns affiliate commissions from some links, which never influence ratings or rankings. Read the full affiliate disclosure.

Follow the author: