Detect plagiarism and texts written by AI: 10 online tools for teachers

Last updated on 18 October 2026

Sunday night, stack of copies. In the middle of a rather laborious second dissertation, a paragraph detonates: impeccable syntax, ‘it should be stressed’, three perfectly aligned arguments. You have a doubt. Wikipedia, a fix found online, or ChatGPT? And above all, how to check quickly without spending the evening?

There are tools for this to detect plagiarism and, since 2023, for Identify texts generated by artificial intelligence. This article, published in 2021, was completely revised in October 2026: much of the original list has disappeared or no longer deserves to be recommended, and new tools have arrived. Here are the ten that remain valid for teachers, from college to university, with what they really cost and what they don’t know how to do.

Before pasting a copy into a detector: four reflexes

A few precautions first, because all these tools have their blind spots.

• A score is not proof. A percentage of similarity signals passages to look at. It does not differentiate between a copy-paste and a quote correctly in quotation marks. For AI, it’s even more fragile (I’ll go back to that below).
• Think about the data of your students. A copy contains a name, sometimes personal items. Remove at least the name before submitting a text online, and be wary of sites that do not clearly say what they do with documents.
• Look who is behind the tool. Many free detectors belong to SEO toolkits that also sell paraphrasers, humanizers that are supposed to make AI text undetectable, or even essay writers.
• Check what your establishment already offers. Many universities, and some high schools, subscribe to Compilatio or Turnitin. This is the safest solution for data.

Locating a copy and paste: plagiarism detectors online

These anti-plagiarism software compare the student’s text to what exists on the web. Redoubtable for copy and paste from Wikipedia or a patch site. Much less for skillful reformulation.

Plagiarisma: free, no account, in almost all languages

It was already in the 2021 version and has not moved on the essentials. Plagiarism accepts pasted text, a web address or a file (PDF, DOCX, ODT, EPUB and many others), without registration for standard checks. It announces more than 190 languages, making it an ally for modern language teachers. You can even choose the engine used for the comparison, Google or DuckDuckGo.

For institutional use, there is a Moodle plugin and a Google Workspace module. Small downside: the same site offers an "try writer" and access to ChatGPT. Not prohibitive, but it says something about the economic model.

Quetext: Plagiarism and AI in the same analysis

Quetext remains one of the most enjoyable places to read a result. The copied passages are highlighted, each correspondence returns to its source. The free version now makes it possible to analyse 1,000 words in plagiarism and 1,000 words in AI detection (the old version of this article was about 2,500 words, that is no longer true). You have to create an account.

Beyond that, the Essential subscription starts at $14.99 per month. And like many others, Quetext also sells an AI Humanizer. So the same editor helps you spot an AI text and make it up. The whole market is kind of like that.

Duplichecker: to troubleshoot, with a reserve

Duplichecker works without registration. You paste up to 10,000 characters or drop a .docx, .txt or .pdf file, and you get a single content percentage with the sources found. There is also a tab for AI detection. To check a suspicious paragraph, that's enough.

What I like less: the page is full of advertisements, paid offers appear with each click, and a ‘Remove plagiarism’ button offers to automatically rewrite the passages identified. He stays on the list because he is struggling. To advise him to students, on the other hand, I would pass my way.

Copyscape: know if a text is already circulating on the web

Copyscape is a veteran. His free search starts from a web address: a practical way to find out if the lectures published on the class blog have been copied elsewhere. To paste text or file a Word or PDF file, you must switch to Copyscape Premium, which is invoiced for searching: 3 cents of dollars up to 200 words, then 1 cent for every 100 words. Cheap, but account and purchase of mandatory credits.

A text written by ChatGPT? AI detectors that work in French

Here, no comparison with a text base. These tools analyze style (sentence regularity, predictable vocabulary) and estimate probability. Even the best are wrong. Scribbr, which publishes one of them, conducted its own study on texts in English: the best paid tool reached 84 % Precision, the best free 68 %. I also introduced ZeroGPT on the blog in 2023, if you are looking for a first filter more.

GPTZero: the pioneer, with a real free plan

GPTZero was launched in early 2023 by Edward Tian, then a student at Princeton. The first version of this article presented him as South African: that was wrong, I correct by the way. I had detailed it on AI Tools. Since then, GPTZero has grown a lot: sentence-by-sentence analysis, Chrome extension, plagiarism check in paid formulas.

The free plan gives the right to 10,000 words per month, enough to spend a small series of copies. French has been supported since a multilingual update, and the publisher announces less than 1 % false positives about French in his own tests. Honestly, I am not sure that French is fully covered in the free plan: some sources reserve it for paid formulas, which start at around 10 euros per month.

Pangram: the detector everyone is talking about

Pangram, it is the name that has been coming up everywhere since the summer. The startup has raised $9 million, and Substack has been using it since July 2026 to flag AI-generated content. Its site highlights evaluations by researchers from the universities of Maryland and Chicago, which rank it among the most reliable detectors. It works in 20 languages, including French, and also identifies passages simply retouched by an AI.

For testing, the free version allows up to 4 checks per day. The individual offer costs $20 per month and adds similarity detection. The scanned texts remain stored while the account is active, but you can remove them from the history, and Pangram claims not to use them to train its templates.

That said, even Pangram is wrong. American essayist Freddie deBoer saw an excerpt from one of his old notes ranked at 100 % as generated by AI. If the most reputable tool of the moment can be wrong about a seasoned author, imagine the necessary caution when it comes to copying a fourth grader.

Scribbr: the simplest for a student who wants to verify himself

The Scribbr AI detector is free of charge, with no limit on the number of analyses, and supports French, English, Spanish and German. The only constraint: 1,200 words per analysis, by pasting the text. Plagiarism is not included: Scribbr’s anti-plagiarism check is charged, starting at EUR 14.95. For a high school student who wants to check their file before returning it, it is a good front door.

Lucide.ai: a detector trained on texts in French

Lucide.ai plays the francophone card. His model is trained on hundreds of thousands of texts in French, and he works only in French. He highlights the suspicious passages page by page, and the academies of Versailles and Bordeaux are among his displayed references.

But there is no free trial, and frankly, it is a lack to get an idea. It takes 19 euros for a 30-day pass without a subscription. The Discovery formula (from EUR 10 per month) is limited to the detection of AI on 1 500 words per analysis; Plagiarism comes only with the Essential offer, at EUR 30 per month. As for the comparison displayed on his site, where Lucide gets 100 % almost everywhere, it is his own test.

Compilatio and Turnitin: first look at what your institution offers

These are the two references of the academic world. A teacher cannot subscribe to it alone, but there is a good chance that your university or institution will already be. Ask your digital referent or look in your ENT or Moodle.

Compilatio, the French solution

Born in 2005 in Haute-Savoie, at the request of teachers, Compilatio team of many French-speaking universities. Magister, the version for teachers, is negotiated at school level, on the basis of a quote. Plagiarism and AI are analysed in the same report, and the data is hosted in Europe, within the framework of the GDPR.

For students, Compilatio Studium allows you to check your own work. The account is free with a first partial analysis (the three main sources), then the credits range from 4.99 euros for 5,000 words to 34.99 euros for 100,000 words. Good point: the documents analyzed in Studium remain invisible to teachers, even those who use Magister. A student can therefore check his memory without fear of his drafts going back to the jury.

Turnitin, the world reference

Turnitin claims more than 16,000 customer establishments. Its strength: in addition to the web and publications, its comparison database contains the work of students already submitted. It is sold only to establishments, without public tariff.

The point here is that, according to its documentation, Turnitin’s AI detection works only in English, Spanish and Japanese. A copy in French will therefore only be entitled to the classic similarity ratio. The publisher itself specifies this: its AI indicator is used to open the discussion with the student, not to decide.

The tools I removed from this list (and why)

Taking the list of 2021 tool by tool, I had a bad surprise with Viper (ScanMyEssay), which I recommended. On his homepage, the editor quietly explains that he uses it to check the work of his own essay writers, with a link to a custom-made memoir service. An anti-cheating detector edited by a ready-made homework seller. The documents analysed are also kept in its database by default, and the old version even published certain tests checked free of charge on affiliated sites. He's off the list.

Other departures are less spectacular:

• PlagSpotter is mainly used to monitor the copy of a website, and its page displays an advertisement for a homework writing service;
• PlagTracker seems to be abandoned, I have not been able to verify that it is still working;
• PlagiarismChecker.co limits the free version to 800 words, blocks ad blockers and itself posts a score of 1.85 out of 5;
• Search Engine Reports and PrepostSeo are two quasi-twin SEO toolkits, limited to 1000 words and full of advertisements and rewriting tools.

What these detectors can't do

They don't see the neighbor's copy. An online detector compares the text to the web: if two students have done the same assignment, they will not know. For that, a comparator like Diffchecker does the case very well. You paste the two copies side by side and the identical passages jump to the eyes.

They do not prove anything about AI. Moreover, these errors do not fall to chance: a Stanford University study published in 2023 showed that several detectors classified as ‘written by an AI’ a majority of writings written in English by non-natives. An allophone student who writes with simple sentences and limited vocabulary is more likely to be misreported. The same is true for a dys student who rightly relies on a proofreader or reformulation tool.

Basically, the detector asks a question, it does not answer it. Asking the student to explain a passage, to show his drafts or the history of his document often raises doubts, in either direction.

Which anti-plagiarism tool to choose according to your need?

In redoing this list, what struck me the most was that the nature of the issue changed. In 2021, it was tracked and copied and pasted from Wikipedia. Today, most of the dubious texts do not exist anywhere else as they were generated for the occasion, and no detector will replace an instruction that obliges the student to show his reasoning. Keep Plagiarism under the elbow for quick checks, test Pangram or GPTZero if you are concerned about AI, and start by asking your institution what is already available.

Frequently asked questions on detecting plagiarism and AI

Is there really free anti-plagiarism software?

Yes, for spot checks. Plagiarisma and Duplichecker work without an account, Quetext offers 1,000 words with a free account. To regularly analyze long files, free versions quickly show their limits.

Can we prove that a student used ChatGPT?

No, no. An AI detector gives probability, not proof, and all produce false positives. The result may justify a discussion with the student, never a penalty on its own.

Do these detectors work in French?

Plagiarism detectors, yes, as they compare texts with each other. For AI, it varies: GPTZero, Pangram, Scribbr, Lucide.ai and Compilatio support French. Turnitin’s AI detection, no.

Can I leave copies of my students on these sites?

With caution. At least remove the name of the student, read what the service does with the documents, and choose your school’s solution where it exists: it is governed by a contract and by the GDPR.

What is the difference between a plagiarism detector and an AI detector?

The first compares the text with existing sources and shows where each copied passage comes from. The second analyses the style to estimate whether an AI has written the text, with no supporting source. The two complement each other, and several tools like Quetext, Compilatio or Pangram now combine the two.