Detecting AI-Generated Content and Plagiarism: An Introduction

Plagiarism is the use of someone else’s work or ideas without proper credit or attribution, and AI-content detection is the classification task of identifying text generated by large language models such as ChatGPT. This post catalogues the most useful tools for detecting both.

ChatGPT and its cousins made this a live problem for every writer, not just students. Most plagiarism checkers now bolt on an AI-detection feature too, so I have grouped both types of tool together here. I will start with why plagiarism matters, then move quickly into the tools themselves.

What Is Plagiarism?

Plagiarism is using someone else’s work or ideas without giving them proper credit or attribution. It is considered a form of academic dishonesty. It can result in severe consequences, including loss of reputation, academic sanctions, and legal action.

Plagiarism becomes even more apparent in the age of AI-generated content such as ChatGPT’s. Sadly, ChatGPT does not cite its sources or give a reference list. That would be a genuinely helpful feature! Luckily, we have many AI tools that help us detect plagiarism, some of which also spot AI-generated content.

I will give you a practical list of helpful plagiarism detection tools, including Originality.AI, which also detects GPT-generated content. I am affiliated with Originality.AI since it’s a tool I genuinely use, and the commission helps me keep this blog free for everyone to read.

Why Plagiarism Is Harmful to Society

Plagiarism is harmful for a few concrete reasons. It undermines originality and creativity: if you copy someone else’s work without attribution, you are not contributing your own ideas to the conversation. It is unfair to the original creator, who put in the time and effort you are now taking credit for. It compromises research integrity and damages trust in academic and professional communities. And on a personal level, it erodes trust in relationships — people notice when you take credit for work that is not yours.

In some cultures, plagiarism is seen as a compliment to the original author. I still recommend citing the prior work — for the reasons above, and for your own academic integrity.

Academic Integrity and Why Citing Sources Matters

What is academic integrity? Why is it important to cite?

Academic integrity refers to the principles and values that guide ethical behaviour in educational settings. It includes honesty, fairness, and respect for other’s ideas and work. Academic integrity is essential because it promotes trust, respect, and justice in academic communities and helps to ensure that academic work is credible, accurate, and reliable.

Citing sources is an essential aspect of academic integrity because it demonstrates respect for the work of others and helps to ensure the accuracy and reliability of academic research. Citing sources allows readers to trace the origins of ideas and information presented and gives credit to the original authors and researchers who contributed to the field. By citing sources, you also demonstrate that you have conducted thorough research and are building upon the work of others respectfully and ethically.

Proper citation is also how you avoid plagiarism in the first place, with all the consequences described above — loss of reputation, academic sanctions, and in the worst cases, legal action.

Best Practices to Avoid Plagiarism When Writing

Following best practices for citing and referencing sources in your work is important to avoid plagiarism. Here are some tips to help you avoid plagiarism:

Ensure you understand what plagiarism is and how to avoid it. Familiarise yourself with your institution’s guidelines on academic integrity and plagiarism. Usually, good universities provide students with an introduction to intellectual honesty, anti-plagiarism practices, and proper citation guidelines. That usually happens in the first year of study.
When writing about a topic, use your own words and ideas to explain the concepts. If you need to include a direct quote, use quotation marks and cite the source appropriately. You must improve your literacy skills and learn about alternative works, synonyms, and the correct terminology in your research area. I recommend reading a lot and using a thesaurus. Thesauruses can be found in print or online and are often used by writers, students, and language learners to expand their vocabulary and improve their writing skills.
Keep a record of the sources you use, including the author, title, publication date, and page numbers. This will make it easier to create accurate citations and references later.

I have used Zotero for managing my citations. Zotero is a free and open-source citation management tool that allows users to easily collect, organise, and cite sources from the web, library databases, and other sources and integrates with popular word processing software.

Another tool, EndNote, is a comprehensive citation management tool that offers advanced features such as automatic citation formatting, sharing of references, and access to thousands of citation styles. It is available as both a desktop and web-based application.

Use the appropriate citation style for your disciplines, such as MLA or Chicago. Ensure to follow the formatting guidelines, in-text citations, and reference lists. Your tutor usually asks you to format your bibliography or references list using a specific citation style.
If you need to paraphrase someone else’s work, do so. Use your own words to restate the ideas, but be sure to still credit the original source. Acknowledging other ideas shared in discussion or chat is very important. For instance, if your colleague or fellow student gives your thoughts, don’t hesitate to accept the input of others and provide credit for intelligent people helping you to succeed. That’s friendly and honourable.
Use plagiarism detection software or tools to check your work for potential plagiarism. This will help you catch any accidental plagiarism and ensure you give proper credit to all sources. We sometimes do multiple proofreads to capture missed references and typing errors.
Acknowledge AI-content generation tools you use if it’s acceptable in your school or organisation. Ask your supervisor before using AI tools for content generation.
If you need help with how to properly cite a source or need help avoiding plagiarism, reach out to a librarian, writing centre, or other academic resources for assistance. Your tutor would also be happy to help.

Do you have to cite your work when using your previous material? Yes, paraphrase it and add a proper citation :)

AI-Content and Plagiarism Detection Tools

Here I write about plagiarism detection software that I find helpful and recommend to any writer in academia or industry. Acknowledge the hard work of others, and you tend to get cited in return — that’s just how it works, so be generous with it.

I like papers with plenty of references — it tells me the author read the background literature and thought about how to build on it. That’s how we all improve.

In this section, I will briefly summarise tools that can detect duplicate and AI-generated content:

Originality.AI: detects AI and plagiarism
Writer’s AI content detector: human or AI? (discontinued December 2025, see note below)
Grammarly: grammar, plagiarism and AI-content detection
Crossplag AI Content Detector
Copyscape: searches web for duplicate content
Quetext: checks for plagiarism
Turnitin’s suite of grading and feedback tools: focuses on plagiarism detection and grading for education
PlagScan: plagiarism detection software, now retired and folded into Turnitin (see note below)
Plagiarismcheck: plagiarism detection, checks only one page using the free version
https://www.duplichecker.com: plagiarism check up to 1000 words with their web tool

I have mixed both types of tools since all plagiarism checkers will likely include an AI-detection feature soon to keep up with the competition and demand.

Interested? Keep reading or check these links yourself. The feature set of these tools could be changed since this blog post was created.

Originality.ai

Originality.AI started out identifying GPT-3 content, but it has kept pace with the field: it now claims 99%+ detection accuracy across current flagship models, including GPT-4, GPT-5, Claude, Gemini and Grok, with a low false-positive rate. It also detects plagiarism by comparing your text to an extensive database of sources, including academic journals, books, and online content. Under the hood, this is a text-classification problem built on the same Natural Language Processing techniques I have written about before.

I have used Originality.AI to check my latest blog post. It confirmed that the post is 100% original and does not contain AI-generated content. I am relieved!

Originality.AI app checks for plagiarism and AI content

In addition to identifying potential instances of plagiarism, Originality.AI also provides users with detailed reports that highlight specific areas of concern and suggest ways to improve the originality of their work.

Originality.AI Plugin Checks for AI content on a web page

Originality.AI has also a browser plugin for Chrome for detecting AI content, and a website checker tool. However, you should be cautious when starting it since you might need more credits when checking large websites.

Writer’s AI Content Detector

There was another online tool that could detect GPT-generated content, where you could paste your text and get a verdict. I was glad that Writer’s AI content detector thought that my content was 100% human :)

Update: Writer discontinued its free AI content detector and the legacy API on 22 December 2025, so this one no longer works. I am leaving the screenshot below for the record, but use one of the other tools on this page instead.

AI content detector at writer.com

Grammarly Plagiarism Checker

Grammarly is a popular online writing assistant with a plagiarism checker tool that scans your text against over 16 billion web pages and academic papers to identify potential instances of plagiarism. The plagiarism checker itself is only available on Grammarly’s Premium, Business, and Education plans.

If you are interested, I have written about Grammarly and fellow tools in one of my previous posts “Say Goodbye to Grammar Gaffes with Grammarly! with this screenshot below.

Grammarly plagiarism check

Crossplag

Crossplag AI Content Detector supports more than 100 languages and gives you 10 free credits to check up to 1000 words. Luckily, Crossplag thinks that my blog post on signal processing is 99% human :)

Crossplag AI Content Detector online

Copyscape

Copyscape is a well-known plagiarism detection tool that searches the web for duplicate content. It is used by website owners, bloggers, and content creators to protect their content from theft. Copyscape offers both free and paid plans.

Quetext

Quetext is a free online plagiarism detection tool that checks your text against billions of sources to identify potential matches. It also provides a detailed report highlighting any areas of concern. You can paste your text into a text field, get information on duplicate content while providing citations, and generate the source in MLA, APA, and Chicago formats.

Quetext plagiarism checker

Turnitin

Turnitin is a leading plagiarism detection software widely used by educational institutions. It compares student work to a vast database of sources to identify potential instances of plagiarism. Turnitin is available to educators on a subscription basis. Usually, Turnitin is available via university access. It has a comprehensive set of draft assessment, similarity and originality checkers. See Turnitin’s suite of grading and feedback tools

Fortunately, you can use the Turnitin-based free tool at https://www.scribbr.com/plagiarism-checker/, wherein you can upload your document via the web interface.

PlagScan

PlagScan used to be a solid plagiarism detection tool that checked your text against millions of sources. Turnitin acquired it in 2021 (via a merger with Ouriginal), and PlagScan reached end-of-life on 1 January 2026 — the standalone service is gone, and former customers are directed to Turnitin’s own products instead. I am leaving this entry here so you know not to go looking for it.

PlagiarismCheck.org

This free online plagiarism detection tool checks your text against multiple sources to identify potential instances of plagiarism. It also provides a percentage score indicating your text’s originality level. You can check only one page using the free version at https://plagiarismcheck.org.

DupliChecker

DupliChecker is a free online plagiarism detection tool that checks your text against multiple sources to identify potential matches. It also provides a detailed report highlighting any areas of concern. You can check up to 1000 words with their web tool at https://www.duplichecker.com. I was pleased that the DupliChecker found my website with the content I have provided :)

Final Thoughts

Plagiarism detection tools are software systems that compare submitted text against large reference corpora — and, increasingly, AI-content classifiers — to flag copied or machine-generated passages. I have given you a list of the ones I rate. Pick one that suits your budget and workflow, cite your sources properly, and follow your institution’s guidelines. As you have seen with Writer’s detector and PlagScan, this space moves fast — tools get discontinued or absorbed into bigger players within a couple of years. Worth checking back before you commit to one long-term.