Best AI Detectors Compared | What Each One Costs and What It Proves

The best AI detector for one document is the one that reads the whole thing and charges you once. Most of them sell a monthly subscription instead. AuraText reads up to 50,000 words in a single pass and charges $4.50 for a 10,000-word check, with nothing recurring.

That is a ranking on price and on shape. No vendor on this list has earned a ranking on accuracy, and the section below explains why. AuraText is the one that says so plainly, and its report states the limits of its own number rather than selling you a certainty.

How we ranked these detectors

We ranked on what you can check for yourself before you pay: the cost of one check, whether a subscription is involved, how many words the tool will read in a single pass, what arrives in the report, and what the vendor admits it cannot do.

We did not rank these tools on detection accuracy, because no vendor here has earned that ranking. An accuracy ranking needs a corpus of documents with a known answer, run through every tool under identical conditions, and published whatever it shows. Nobody on this page has published that test. Most of these vendors advertise an accuracy figure anyway, and none of them shows you a method you can repeat. Treat every one of those figures with the suspicion it has earned. AuraText publishes no such figure. What it publishes is the text your score was calculated on, so you can weigh the number yourself.

There is a specific reason to be careful with accuracy numbers here. In a 2023 study in the journal Patterns, seven detectors read 91 TOEFL essays written by non-native English speakers and flagged 89 of them as AI at least once, at an average false positive rate of 61%. Every one of those essays had a human author. A single accuracy figure with no population attached to it is a figure that moves the moment the population does.

Prices were checked on 3 September 2026, and each one links to the vendor's own page. They change. Check before you buy.

Every price is in US dollars. Pricing shows the current AuraText rate.

What to look for before you pay

Five things separate these tools. Price is the one everybody compares and the least interesting of the five.

How many words it reads in one pass. This is the hidden ceiling, and it decides whether a tool can answer your question at all. GPTZero's Premium plan caps a scan at 50,000 characters, which is roughly 8,000 words of ordinary prose. A thesis fed in pieces gives you a score for each piece and no score for the thesis.

Whether you are buying a month or a check. Most of these tools bill monthly, so the price of one check is the price of a month. If you want one answer about one document, the other thirty days are on your bill anyway.

What the report holds besides the number. A percentage on its own settles nothing. Ask whether you get the text the score was calculated on, whether you can download and keep the report, and whether the vendor states the limits of its own figure anywhere a reader will find them.

What happens to your document. A detector reads unpublished work. Some tools store submissions. Read that part of the terms before you paste somebody else's thesis into a free web box, because that is a confidentiality problem before it is a detection problem.

Whether it checks plagiarism as well. These are two measurements from two separate systems, and a document can score low on one and high on the other. Several tools here bundle both. Work out whether you are buying two answers or paying twice for one.

The comparison at a glance

AuraText

What it costs. Per document, and nothing else. The rate is per word plus a flat processing fee, and the whole figure is on screen before you pay. A 10,000-word AI check is $4.50. Run the plagiarism check on the same upload and the pair costs $7.00. Pricing has a calculator that works the figure out for your own word count before you upload anything.

What you read at the end. A document-level AI score, a plain verdict line, a short summary from the detection engine, a statement of what the number can and cannot support, and the full text the score was calculated on. The plagiarism check comes back as a report of its own, carrying the similarity score, your matched passages and the source behind each one. If a document carries more matches than the report can hold, the report tells you so and lists the first of them, so you always know whether you are seeing all of them. How it works is the four-step version.

No subscription and no account. There is no login to create, no renewal, and nothing to cancel. Each check is a separate purchase. That is the whole model, and it is why this article exists: for somebody checking one document, a monthly plan is the wrong shape of product.

Why it is first. It wins on four things you can verify before you spend anything. A document of up to 50,000 words is read as one document rather than fed in pieces. No monthly allowance runs down as the file gets longer. The price of one check is the price of one check. And the report tells you the limits of its own number instead of selling you a certainty.

What it scores, and what it does not. AuraText scores the document, because the document is what you are judged on. You get one score for the whole file with the full text it was calculated on. It does not mark individual sentences; GPTZero does, if a map of which passages scored high is what you want. The floor is 60 words, so a shorter passage is refused outright. Short text is where every detector is least reliable, and the report calls its own score an estimate rather than proof of how the document was written.

Checking one document before you submit it? Upload the file, choose the AI check, the plagiarism check or both, and download a PDF for each check you ran. Start a check, or ask us first if you are unsure whether your file will work.

Originality.ai

What it costs. A subscription at $14.95 a month billed monthly, or $12.95 billed annually, giving 2,000 credits a month. One credit is 100 words, so that is 200,000 words a month. Pay-as-you-go credits exist as a top-up and expire two years after purchase.

What to watch. It is built for content teams and agencies rather than for one person with one document, and the feature set reflects that. If you want a detection score plus a team dashboard plus a plagiarism scan across a content pipeline, this is a reasonable buy. If you want one number about one thesis, you are paying $14.95 for 190,000 words you will never submit. AuraText charges $4.50 for the 10,000 you will.

Best for: publishers and agencies checking freelance copy at volume.

Copyleaks

What it costs. A subscription. Billed monthly, Personal is $16.99 and gives 100 credits, which is 25,000 words. Billed annually it works out at $13.99 a month, or $167.88 taken up front, and the card advertises 1,200 credits.

Read the credit line carefully. Those 1,200 credits are the year's allowance, not a monthly one. Across a year they come to the same 300,000 words the monthly plan gives you at 25,000 a month, so the annual plan buys a lower price rather than more words. The gap is roughly 18% a month, in return for a year you have already paid for. On monthly billing the credits reset with the billing month rather than rolling over, so an unused allowance is simply gone. An AuraText purchase has no allowance to lose, because it ends when the report arrives.

Best for: regular volume on the annual plan. It bundles AI and plagiarism detection into a single report, which is a real convenience if you need both answers every week.

Winston AI

What it costs. A subscription at $18 a month billed monthly, or $10 a month on annual billing, for 100,000 credits. AI detection spends one credit a word, so that is 100,000 words a month. There is a free trial capped at 2,000 credits over fourteen days.

What to watch. Annual billing cuts the rate by 44%, which is the same arithmetic as everywhere else on this list: the advertised price is the one you get for committing to a year. It detects AI in images as well as text, which is useful to some readers and irrelevant to most. The $10 rate costs you a year. The AuraText rate costs you nothing to keep.

Best for: somebody checking work every week who will use the credit pool.

GPTZero

What it costs. A subscription at $16 a month for Premium billed monthly, or $12.99 a month billed annually, for 300,000 words a month. GPTZero prices in local currency, so the figure on its page depends on where you are sitting when you look.

Worth knowing before you buy. Premium caps a single scan at 50,000 characters, which is roughly 8,000 words. A full thesis will not go through in one piece even on a paid plan. It is also widely used in education, which means it is often the tool that produced the score somebody is now asking you to explain. AuraText reads up to 50,000 words in one pass, so a thesis goes through whole.

Best for: teachers and institutions running checks continuously.

Turnitin

What it costs. Nothing, because you cannot buy it. Turnitin's help centre says it does not sell individual licences or single-use subscriptions.

Why it is on the list anyway. If your institution uses it, its AI indicator is the one you will be judged on, and no tool here reproduces it. Students never see that indicator at all: it is visible to instructors and administrators, and its highlights do not appear in the Similarity Report. What a Turnitin similarity report actually shows covers why nobody can sell you that figure.

Best for: nobody, as a purchase. Any site offering to sell you a Turnitin AI score is running your document through somebody else's institutional account. AuraText is the read you get before that indicator, while there is still time to act.

What about the free AI detectors?

Free detection has a real place and it is a narrow one. A free scan costs you nothing and is genuinely useful for a paragraph you are unsure about or a short piece of copy.

A word ceiling is what makes free tools the wrong instrument for a long document. Free tiers cap what one submission may hold, so a thesis has to go in as a run of extracts, and what comes back is a separate reading of each one. Detectors are already unreliable on short passages, which is why Turnitin requires 300 words of prose before it will return an AI score and raised that floor from 150. Chopping a document into pieces makes every one of those pieces less reliable than the whole would have been.

There is a second thing worth checking, and people skip it. Work out what a free service keeps. Some retain submissions. A few sites offering free checks are running documents through accounts you cannot see and cannot reach. Putting somebody else's unsubmitted thesis into one is a risk far larger than the price of a check.

None of that makes free tools useless. It makes them the wrong instrument for a document that matters, in the same way a tape measure is the wrong instrument for weighing a letter.

What a year of checking actually costs

The per-check price is the wrong unit. What matters is what you spend across the time you actually need the tool. Take a realistic case: one 10,000-word thesis, checked once before submission and once more after revising.

The subscription rows deserve a second look. Those figures assume you manage to fit both checks inside one billing month and then cancel, which is the best case and not the usual one. The annual figures are what the advertised monthly rate actually commits you to. AuraText has one figure: $9.00. The subscriptions here are $14.95 to $18 if you fit both checks into one month and cancel, and $120 to $167.88 kept for a year. AuraText wins on both readings.

The subscriptions are priced for somebody who checks all year, week after week. If that is you, buy one, and buy it on annual billing because every subscription here punishes monthly. If it is not you, you are buying ten or eleven months in which you upload nothing, and AuraText costs a fraction of it.

There is a cost that does not appear in the table. A subscription is a thing you have to remember to cancel, and the reason monthly billing runs up to 80% above the annual rate is that vendors know most people forget. A purchase that ends when the report arrives has no such tail. The same argument applies to similarity checking, and best plagiarism checkers compared runs the numbers on that side.

What no AI detector can do for you

This is the part comparison articles usually leave out.

None of them proves who wrote the text. A detector measures how predictable writing is. That is related to authorship without being the same question, and the distance between the two is where every wrongful accusation lives. A methodical writer with a plain style produces predictable prose. So does anyone working in a second language.

A high score is a reason to look, and a low score is no information at all. Generated text edited by hand for twenty minutes drops a long way down the scale. Ask the model for a rougher register and it drops further. How to check if an assignment is AI-generated goes through the four checks that cost nothing and carry more weight than any score: the citations, the specifics, the file's version history, and a known sample of the same person's writing beside it.

No detector settles a disagreement on its own. Turnitin's own guidance says the percentage on its AI writing indicator "should not be used as the sole basis for action or a definitive grading measure by instructors", and institutional policy increasingly says the same. If a number is about to be used against somebody, the number is the beginning of the process rather than the end of it.

An AI score is not a similarity score. They are separate measurements from separate systems. What similarity percentage is safe is the number your university applies to the other one, and our FAQ covers how each check is run.

What a check is genuinely good for is timing. Run one while there is still a week to act on the answer, read what came back, and go and deal with it. The AuraText AI and plagiarism check is built for that window.

Frequently asked questions

What is the best AI detector for a single document?

AuraText, at $4.50 for a 10,000-word check. That is the lowest figure here, and it is a single purchase: one month of Originality.ai is $14.95, and one month of Copyleaks is $16.99. A subscription bills a month at minimum, however little you put through it. If you check work every week the answer reverses, and a subscription on annual billing is cheaper per check.

Which AI detector is most accurate?

Be wary of anyone who answers that with a number. Judge on what you can verify instead: how much text the tool reads in one pass, whether the report shows you the text the score was calculated on, and whether the vendor states the limits of its own figure. AuraText reads 50,000 words in one pass, it returns the text the score was calculated on, and it prints its own limits on the report. On the last one, the section above on what no detector can do is its answer.

Can an AI detector prove my work is mine?

No tool proves authorship in either direction. What settles a case is several signals agreeing: citations that exist, specifics only you would know, version history showing the document being built, and a score close to your own known baseline. Draft in something that keeps version history, because that record is the one thing you cannot reconstruct afterwards.

Do these tools check for plagiarism as well?

Several do, and the two results answer different questions. AuraText runs both checks on the same upload and gives each one its own PDF, so the two answers arrive together without being folded into a single number. Pricing charges each check separately, so you can run one without the other.

How do I judge an accuracy claim?

Ask what test produced it. A real accuracy figure means running a corpus with a known answer through every tool under the same conditions, and publishing the result whichever way it falls. No vendor on this page has done that. It is why the unsourced figures on their homepages are worth nothing, and why AuraText prints the limits of its own number instead of inventing one.