GPTZero vs Originality.ai vs Copyleaks: which is right?

Three names come up in almost every conversation about AI text detection: GPTZero, Originality.ai and Copyleaks. They are usually presented as interchangeable, and they are not. One was built for classrooms, one for people who buy content by the word, and one for institutions that need the result to appear inside Canvas or Moodle without anyone copying and pasting.

Lacewing Technologies is an AI and software development company in Navi Mumbai. We build and operate our own products alongside client work, and one of those products is a detector, so we read competitor pricing pages more often than is healthy. This post is what we found on 3 November 2026, taken from each vendor's own pricing or documentation pages. Where a page would not load for us, we say so rather than fill the gap from a review site.

Who is each detector actually built for?#

GPTZero sells to education first. Its FAQ calls it "the most trusted AI content checker in education, both for teachers and students", and the home page describes itself as an official AI detector partner of the American Federation of Teachers. It also lists publishers, recruiters, copywriters and marketers as users, but the product decisions, from Writing Replay to the Canvas integration, are classroom decisions.

Originality.ai sells to people who publish. The AI checker page says it is "Built for the unique needs of enterprise, high-volume web publishers, agencies, and schools", and the home page tagline reads "AI & Plagiarism Detector for Serious Content Publishers". Credits are priced per 100 words, which is how content buyers already think.

Copyleaks sells to institutions and platforms. Its developer documentation names education, publishers and user-generated-content platforms as the three target uses. Its distinguishing feature is reach into learning management systems and a sizeable API surface, not a consumer scanner.

If you remember nothing else from this post, remember that framing. Most disappointment with detectors comes from buying one built for somebody else's job.

How do pricing and free tiers compare?#

This is where honesty gets awkward, because we could only verify two of the three pricing pages.

GPTZero. The pricing page we fetched rendered only the Professional Team Plan: "500,000 words per member, per month", minimum two seats, card payment only. The individual plan prices are drawn in the browser and did not appear in the page we could read, so we are not going to quote dollar figures for them. Third-party review sites disagree with each other on those prices by several dollars a month, which is exactly why we will not repeat them. What the vendor does state plainly: the free scanner on the home page accepts up to 10,000 characters per check, and the FAQ says a free account raises that to texts of 150,000 characters or a batch of 250 files.

Originality.ai. The pricing page lists three plans. Free: $0, 100 credits (about 10,000 words) on a one-time basis, no API, no team seats. Pro: $14.95 a month billed monthly or $12.95 a month billed yearly, 2,000 credits a month (200,000 words), with file upload, bulk scan, shareable PDF reports and 30-day history. Enterprise: $179 a month billed monthly or $136.58 a month billed yearly, 15,000 credits a month (1.5 million words), with API access and a year of scan history. One credit covers 100 words of AI checking; a combined AI and plagiarism check on 100 words costs 2 credits. Purchased top-up credits expire two years after purchase.

Copyleaks. Its pricing page and its marketing pages returned a bot-protection block to every fetch we attempted on 3 November 2026, so we have no verified prices to give you. Its developer documentation is open, and that is where the rest of this post's Copyleaks facts come from. The API endpoint has a free sandbox mode "to test your integration with the Copyleaks API for free", and the docs say you are only charged for successfully completed scans. For credit prices, open the pricing page in a browser yourself and note the date.

An honest comparison has holes in it. We would rather show you the holes than paper over them with a number copied from a review that copied it from another review.

What are the per-scan limits?#

Vendors talk about words per month. What actually bites in practice is the ceiling per scan, because a 12,000-word thesis chapter or a 400-page PDF either goes through or it does not.

GPTZero: the API reference states "On API plans, the limit is 150,000 characters", and longer text is rejected with a 400 error. The free web scanner stops at 10,000 characters without an account.

Originality.ai: the AI checker page states a minimum, not a maximum: "we have a 100-word minimum", with the note that "Shorter text may impact accuracy." We did not find a published per-scan maximum on the pages we read.

Copyleaks: the AI text detection endpoint requires between 255 and 100,000 characters per request. The general technical specifications page sets a ceiling for submitted documents of 2,000 pages, counted at up to 250 words a page, which the page summarises as 500,000 words.

For an Indian college checking a 60-page dissertation, those numbers matter more than the headline price. For an agency checking 800-word blog posts, none of them will ever be reached.

What does the report actually show?#

A bare percentage is the least useful thing a detector can return. Here is what each one adds.

GPTZero describes "a sentence-by-sentence classifier" that "calculates the probability that a text was created by AI". The FAQ lists confidence scores, AI vocabulary and sentence-by-sentence highlighting, and the API returns a predicted class of human, AI or mixed with class probabilities and a confidence category. The education-specific extra is Writing Replay, which the home page describes as a video of the writing process showing copy-and-paste events and typing patterns. A plagiarism checker exists but is listed as a separate premium feature, not part of the AI report.

Originality.ai highlights sentences ("See which sentences are most likely AI with highlights"), returns a split of likely AI, likely original and mixed, and can produce a shareable link or PDF. Plagiarism is bundled into the same credit system: the same scan can run both checks for 2 credits per 100 words. A Deep Scan mode promises to show "why text is likely flagged as AI and how to ethically edit it".

Copyleaks returns results per section, each with a classification and a probability, plus an overall human-versus-AI summary. The explanation layer, AI Logic, is where it differs: when enabled, the response includes a patterns object with statistics on AI-like and human-like phrasing. The vendor's July 2025 press release describes two parts, AI Phrases, which highlights language that appears more often in AI text, and AI Source Match, which checks whether a passage matches AI-generated content already published online. The docs are clear that AI Logic explanations are returned for six languages only.

Is there an API, and what languages are covered?#

A few notes on the table.

API access is the sharpest split. GPTZero and Copyleaks treat the API as a front-door product. Originality.ai reserves it for the $179-a-month Enterprise plan, so a developer who wants to automate a few hundred checks a month is pushed to one of the other two or to an alternative.

Language coverage is where Indian buyers should pay attention. Copyleaks publishes an explicit list of 30 ISO-639-1 codes for AI text detection, and Hindi (hi) and Bengali (bn) are on it. Marathi, Tamil, Telugu, Gujarati and Kannada are not. GPTZero names five languages as fully supported, all European, and routes non-English text to a multilingual model. Originality.ai says its 5.0 models identify multilingual text automatically but we found no language list on the pages we read. If your content is in an Indian language other than Hindi or Bengali, none of the three publishes a claim you can hold them to.

LMS reach favours Copyleaks by a wide margin. Its own press release names seven platforms, and its Moodle plugin on the Moodle marketplace states support for Moodle 3.5 through 5.3. GPTZero's integrations page names Canvas and Google Classroom. Originality.ai's home page mentions a Moodle plugin and Google Classroom.

What does each vendor say about accuracy and false positives?#

Every one of these figures is the vendor describing its own tests. We repeat them because you will see them in sales conversations, not because we endorse them.

GPTZero claims "99.9% accuracy" on its home page, and the technology page states "We keep GPTZero's false positive rate at no more than 1% when evaluating AI versus human text." The FAQ adds a more useful detail: when the confidence category is high, 99.1% of human articles are classified as human, and "there always exist edge cases with both instances where AI is classified as human, and human is classified as AI." The technology page also says the model "performs best of longer texts and English prose", which is the most honest sentence on any of the three sites.

Originality.ai says "Originality.ai 5.0 has 99%+ accuracy" and the same for 5.0 Max, on a page that also warns readers "Don't trust a SINGLE 'accuracy' number without additional context" and walks through confusion matrices, recall, specificity and F1. It publishes false-positive rates for its retired models (0.5% for Lite, 1.5% for Turbo, 2.4% for Multi Language 2.0) but not, on the pages we read, for 5.0. Its home page also states that "An AI score shouldn't be used alone for academic integrity discipline."

Copyleaks says on its developer product page that the detector was independently tested and "shown to have exceptional accuracy in identifying AI-generated text, with very low false positive rates", with no figure on that page and a link to a separate methodology document we could not open. Its marketing pages, which are the ones that normally carry specific percentages, were behind bot protection when we tried.

Notice what all three have in common. The claims are about distinguishing AI from human text across a test set, usually long and usually English. None of them is a claim about mixed authorship, about a 300-word paragraph, or about an engineering student from Pune whose careful English reads as formulaic. Those are the cases that actually land on a teacher's desk.

Which should you pick, by persona?#

A teacher or college department. If your institution already runs Moodle, Canvas, Blackboard or Brightspace, Copyleaks's LMS coverage removes the copy-paste step that is where most misuse begins. If you want to see how a student wrote rather than only what they wrote, GPTZero's Writing Replay and Google Classroom integration are built for that. Either way, read the vendor's own warning: Originality.ai says a score should not be used alone for discipline, and the same applies to the other two.

An SEO agency. Originality.ai is the one priced in your unit of account. Credits per 100 words, plagiarism in the same scan, shareable PDF reports for the client, 2,000 credits a month on Pro. The API being Enterprise-only is the catch if you want to wire detection into a publishing pipeline; for that, GPTZero's or Copyleaks's API is more accessible.

A publisher. Volume and workflow decide it. A newsroom checking 50 pieces a day wants batch upload and an API, which points to GPTZero or Copyleaks. A smaller publication paying freelancers per article is well served by Originality.ai's Pro plan and its bundled plagiarism check.

A freelance writer. You mostly want to know what a client's detector will say before they run it. Originality.ai's free 100 credits and GPTZero's 10,000-character free scanner both cover a short article. Scan, read the highlighted sentences, and rewrite for rhythm and specificity where the highlighting clusters, because that is what the models read as human. That tends to lower a score; it is not a guarantee, and if a client or institution requires disclosure of AI use, disclose.

An Indian SMB. Three questions. What language is the content in? If Hindi or Bengali, Copyleaks is the only one of the three that lists it. What is your monthly volume? If it is a dozen blog posts, a $15-a-month plan is 1,250 rupees or so for something you will under-use, so look at pay-per-use or an INR-priced alternative. Do you need an API? If yes, Originality.ai's Enterprise price rules it out at SMB scale.

If none of the three fits, the market is wider than three names. Six worth a look, in no particular order of merit:

1. GPTZero, for classrooms, Writing Replay and a free scanner that handles 10,000 characters.
2. Originality.ai, for publishers and agencies who want per-100-word credits and plagiarism bundled.
3. Copyleaks, for LMS-first institutions, 30 languages and a developer API with a free sandbox.
4. Winston AI, which claims 99.87% accuracy on its home page, lists 14 languages, allows 200,000 characters per scan on every plan and offers a 14-day free trial of 2,000 credits. List prices are $18, $29 and $49 a month, with a discount code shown on the page at the time of our fetch.
5. TextSight, which we build. Free tier of 1,500 words per scan; Starter at $9.99 a month or ₹899 in India for 5,000 words per scan; Pro at $19.99 or ₹1,799 for 7,500 words per scan with API access. It returns a score plus the passages that drove it and is explicit that the output is a signal for review. No free trial, and no Indian-language detection claim either. Details at textsight.ai.
6. Sapling, whose free detector covers 2,000 characters, with a Pro plan at $25 a month or $12 a month billed yearly that raises that to 100,000 characters. Its API is usage-based with a $5 minimum. Its own page says plainly that "False positives and negatives may occur."

How should you treat the score once you have it?#

The same way in all six cases. A detector returns a probability that a passage looks like the machine text it was trained on. It does not return authorship.

Use the score to decide where to read closely, not what to conclude. Look at the highlighted sentences and ask whether they are a quoted definition, a template paragraph or a disclaimer, because those score as machine-like whoever wrote them. Pair the result with drafts and version history, which are more probative than any percentage. And if a flag would trigger an automatic penalty, whether an academic charge or a withheld payment, do not let a number carry that weight on its own.

Every vendor on this page says some version of that in its own small print. Originality.ai says the score "shouldn't be used alone". GPTZero says edge cases always exist. Sapling says false positives may occur. Believe them on that point, even when you are sceptical of the 99-point-something next to it.