Best AI detector in 2026: how 9 popular tools compare

"Which AI detector should we buy?" is a question we hear from colleges in Navi Mumbai, from content agencies in Pune and from freelance writers who have been asked to prove their own work is human. The honest answer is that it depends on what you are checking, how much of it, and what happens after a flag. This guide walks through nine widely used tools, grouped by the job they do well, with every price and limit taken from the vendor's own pages on 3 November 2026.

Lacewing Technologies is an AI and software development company in Navi Mumbai. We build client systems, and we also build and operate our own products, one of which is an AI detector. That makes us a participant in this market rather than a neutral observer, so we have put our own tool in the middle of the list, stated its limits alongside everyone else's, and kept to figures you can check yourself.

How should you choose an AI detector?#

Before the list, the criteria. Most comparison articles rank on a claimed accuracy figure. We do not, because every vendor's number comes from a test set they chose, and the differences between them are smaller than the difference a 300-word essay makes to any of them.

What actually separates the tools:

Sentence-level highlighting. A single percentage is almost useless. You need to see which passages drove the score so a human can check whether the flagged section is a quoted definition, a standard disclaimer or something worth asking about. Most paid tiers offer this; several free tiers withhold it.

False-positive handling. Does the vendor publish a false-positive rate, a minimum length, and guidance on what to do with a flag? Turnitin and GPTZero both do. Several others publish only an accuracy claim.

Document length. Detectors need a sample. Turnitin set its minimum at 300 words to keep its document-level false-positive rate under 1%. Originality.ai sets a 100-word floor. The maximum matters too: a 20,000-word thesis will not fit in a 2,000-character box.

Pricing unit. Some vendors meter words per month, some credits, some characters per scan. Work out your monthly volume in words, then convert each plan to that figure before comparing prices.

API and integrations. A content team scanning 400 articles a month needs bulk upload or an API, not a paste box.

Languages. Most detectors are trained and evaluated on English. Support for Hindi, Marathi and other Indian languages is rare, and code-switched text is weaker still.

Which tools fit which use case?#

Here is the list. The numbers are an order of discussion grouped by use case, not a verdict on quality.

1. Turnitin: education, where the institution already pays

Turnitin is the default in higher education because it sits inside the submission workflow. Its AI writing detection is, in the vendor's words, "available with Originality", its institutional integrity product. There is no public price list on the pages we could reach, and GPTZero's own comparison notes that Turnitin "does not offer individual memberships". If you are a student or an independent tutor, this one is not for sale to you.

What Turnitin publishes is unusually specific. Its Chief Product Officer wrote that the minimum length was raised "from 150 to 300 words", that "our document false positive rate is less than 1%" for documents with over 20% AI writing, and that "our sentence-level false positive rate is ~4%". Scores under 20% carry an asterisk because they are less reliable. A separate Turnitin post says the tool "does not make a determination of misconduct" and that educators "will need to apply your professional judgment". That is the right framing, and it is one worth holding every other vendor to.

2. GPTZero: education and students, with a usable free tier

GPTZero is the most common choice where Turnitin is not licensed. Its support pages state the free plan gives "10,000 words a month", "up to 10,000 characters per scan" and "up to 3 files in a batch upload", with one free Advanced Scan for sentence-level highlighting. The Essential tier allows scans "up to 50,000 characters"; Professional allows "up to 150,000 characters" and batches of 250 files.

Prices on the pricing page render dynamically, so we took them from GPTZero's own comparison article: Premium at $12.99 a month and Professional at $24.99 a month, both quoted as the monthly rate when billed annually. GPTZero lists full support for English, German, Portuguese, French and Spanish. Its FAQ is also candid: results "should not be used to punish students", and "the sentence-level classification should not be solely used to indicate that an essay contains AI".

3. Originality.ai: publishers and SEO teams

Originality.ai positions itself for "Serious Content Publishers", and its pricing follows that audience. One credit scans 100 words. The Pro plan is $14.95 a month, or $12.95 a month billed yearly, for 2,000 credits (200,000 words). Enterprise is $179 a month, or $136.58 billed yearly, for 15,000 credits and API access. New accounts get 100 free credits, roughly 10,000 words.

It highlights "which sentences are most likely AI", sets a 100-word minimum, and its current models "automatically identify multilingual text". It also notes, to its credit, that "false positive rates can vary by AI detection model and brand". For an SEO team checking freelance submissions before publication, the credit model and team management fit well. For a teacher, the per-word metering is awkward.

4. Copyleaks: enterprise and multilingual teams

Copyleaks is the most multilingual tool here. Its API documentation lists 30 supported languages for AI text detection, with sentence-level explanations ("AI Logic") available in six of them: English, Spanish, French, Portuguese, German and Italian. Pricing is credit-based, and the API docs define the unit: "1 credit = 250 words".

We could not retrieve the public pricing page by automated fetch on our access date, and search snippets of it carried figures of uncertain age, so we quote no plan price. Treat Copyleaks as a quote-and-trial purchase and ask sales for a current rate card, particularly if you need LMS integration or API access, which the vendor routes through sales anyway.

5. TextSight: individual writers and small teams

TextSight is our own detector, so read this section as a vendor describing its product. It returns a document score with a confidence score for every sentence, colour-coded in the text, and its own FAQ tells users to "treat any score as one signal, not proof". The free tier allows 1,500 words per scan with an account (1,000 without), capped at three actions a day, and withholds sentence-level highlighting. Starter is $9.99 a month, or $7.49 billed annually, and ₹899 a month in India, for 5,000 words per scan. Pro is $19.99 a month, or $14.99 annually, ₹1,799 in India, for 7,500 words per scan plus API access at 5,000 calls a month. Business ($39.99) and Enterprise ($79.99) raise the cap to 10,000 and 15,000 words per scan.

The limits are real. The detector is English-only; the multilingual support on the site applies to the humanizer, not the detector. There is no free trial of paid tiers. And at 1,500 words, the free scan is smaller than QuillBot's by word count, though larger than Sapling's. Where it fits is a writer or a small Indian team that wants rupee billing, per-sentence detail and a tool that was designed around review rather than verdicts.

6. Winston AI: small teams that want multilingual checks

Winston AI prices in credits per month: Essential 100,000, Advanced 200,000, Elite 500,000. On our access date the pricing page showed a 50% promotion ("50% off with code WINSTON50"), with regular prices of $18, $29 and $49 a month and discounted prices of $9, $14.50 and $24.50. The free tier is 2,000 credits over a 14-day trial, so it is a trial rather than a free plan. Every plan allows up to 200,000 characters per scan, which is the largest per-scan cap in this guide, and API access is listed on all tiers.

Winston names English, Spanish, Chinese (simplified), German, Polish, Portuguese, Italian, Ukrainian and Dutch for multi-language detection. The accuracy marketing is qualitative rather than numeric, which we count as a point in its favour.

7. Sapling: developers who want an API first

Sapling's detector is the simplest to evaluate because the limits are plain. The free version checks "2,000 characters" per scan, roughly 300 to 400 words. Pro is $25 a month, or $12 a month billed annually, and allows up to 100,000 characters per check. Enterprise starts at 10 seats at $15 a seat. It offers a "Show sentence scores" view, and the API, billed separately per character with a $5 minimum, accepts up to 200,000 characters per request.

For a product team adding detection to its own workflow, Sapling's API-first model is the most direct route. For a teacher pasting essays, the 2,000-character free box will frustrate quickly.

8. QuillBot AI Detector: free checks with explanations

QuillBot's detector is free for "up to 1,200 words per scan; six free scans per day" with no sign-up. It supports six languages (English, French, Spanish, German, Dutch and Portuguese) and reports four categories: generated by AI, generated and refined by AI, written by a human and refined by AI, and written by a human. The free version shows one sentence-level explanation per scan; Premium explains every highlighted sentence and adds bulk upload. Premium is $19.95 a month, $39.95 every three months, or $99.95 a year ($8.33 a month).

The AI-refined category is genuinely useful for understanding mixed authorship, and the free limit is the most generous word count in this list. The catch is that Premium is a writing suite, so you are paying for a paraphraser and grammar tools whether you want them or not.

9. ZeroGPT: quick anonymous checks, with marketing to discount

ZeroGPT's homepage offers a 15,000-character box and highlights "every sentence written by AI" with a gauge. The pricing page shows a free plan at "$0 forever", Personal and Business/EDU tiers with "40% off annually", an Enterprise tier and a pay-as-you-go API, but no dollar figures for the paid tiers rendered on our fetch. The homepage claims "98.4% detection accuracy" and a false-positive rate under 1%, with no methodology linked.

As a free check on a paragraph you are curious about, it does the job. As a basis for any decision about a person, the lack of published methodology and the absence of a minimum-length policy should give you pause.

Comparison table: pricing, free limits and per-scan caps#

All figures from vendor pages fetched on 3 November 2026. Prices are USD except where the vendor publishes rupees. "Not published" means the figure was not on the page we could reach, not that it does not exist.

Two things stand out. First, almost nobody publishes Indian pricing. Of the nine, only one shows rupee plans, and international card fees and GST will add to the sticker price for everyone else. Second, the pricing unit varies so much that the cheapest-looking plan is rarely the cheapest for your volume. A team scanning 60 articles of 1,500 words a month needs 90,000 words: that is 900 credits at Originality.ai, 360 credits at Copyleaks, and 18 scans at a 5,000-word cap elsewhere.

Why should no detector be the sole basis for a decision?#

Because every tool in this list measures statistical regularity, not authorship.

Language models produce smooth, predictable text. Detectors look for that smoothness. The problem is that some humans write smoothly too: students taught to a rubric, engineers writing documentation, and anyone writing carefully in a second language. In an Indian classroom, that last group is most of the room. A detector that flags careful, plain English will flag exactly the students least able to argue back.

The vendors themselves say so when you read past the landing page. Turnitin's sentence-level false-positive rate of around 4% means that in a 50-sentence essay, two highlighted sentences may be perfectly human. GPTZero says its results "should not be used to punish students" and recommends asking students "to demonstrate their understanding in a controlled environment" instead. Originality.ai notes that false-positive rates vary by model and brand.

So what should a flag trigger?

• More attention, not a penalty. Read the piece. Compare it with the author's earlier work. Ask about it.
• Process evidence. Drafts, version history in Google Docs or Word, and the author's ability to explain their choices are all more probative than a probability.
• A second signal. Run the text through a second detector. If two tools built on different training data disagree, that disagreement is information.
• Disclosure, where it is required. If an institution or client requires AI use to be declared, declare it. Rewriting for rhythm and specificity tends to lower detection scores because that is what detectors read as human, but it is not a guarantee, and it is not a substitute for the disclosure a policy demands.

A workflow where a number alone leads to a failing grade, a rejected article or a withheld payment is a workflow that will eventually be wrong about someone who cannot afford it. Design around that.

What we would tell each kind of buyer#

A college in India. If you have Turnitin, use it, follow its 300-word and 20% guidance, and train staff on the conversation that follows a flag. If you do not, GPTZero's free tier is enough for spot checks, and no tool justifies a misconduct finding on its own.

A publisher or SEO team. Originality.ai or Copyleaks if you need credits, team seats and multilingual coverage; Winston if you want the largest per-scan cap. Budget in words per month, not dollars per plan.

A freelance writer asked to prove their work. A free check on QuillBot or ZeroGPT shows what a client is likely to see. If you want per-sentence detail and rupee billing, our own tool is one of the options at around ₹899 a month. Keep your drafts: they are better evidence than any score.

A developer. Sapling for the simplest API, Winston for API on every tier, or GPTZero's separately priced API. Check per-request character limits against your longest document before you commit.

Whatever you choose, re-check the pricing page before you pay. Three of the nine pages in this guide could not be fetched by an automated request on the day we wrote it, and promotional pricing on at least one of them changes the headline figure by half.