The spread of text plagiarism is one of the most pressing problems of the information age. Fortunately, modern technologies make it possible to combat the appropriation of someone else's intellectual property quite successfully. The most effective tools to counter this phenomenon are plagiarism detectors. In this article, we will talk about the principle of their operation and capabilities. You will learn whether plagiarism checkers are accurate and which services will be most popular in 2024.

How Do Plagiarism Checkers Work?

Plagiarism detectors analyze the text sent to them and check it for matches with other texts from the Internet or an internal database. Based on the results of the check, they calculate the percentage of uniqueness, highlight non-unique fragments, and provide sources of plagiarism. Such services are divided into universal and developed for a specific area. Some are tailored for web content and equipped with tools for analyzing SEO parameters. Others focus on scientific articles and have access to a solid database of academic materials. The latter are especially often used in the fields of science and education.

Most plagiarism detectors check text using 4 criteria:

  • Keywords. The service monitors the presence and location of keywords in the text to find signs of plagiarism based on this parameter. If the program sees the same keywords in similar places in other texts, this indicates plagiarism.
  • Phrases. The platform operates according to the same scheme. The only difference is that it finds in the text not keywords but phrases with the same sequence of words. When a certain threshold of identical phrases is reached, the tool identifies them as plagiarism.
  • Content. The system examines the style and tone of the text, as well as sentence structure. After that, it compares it with other content according to the specified parameters and calculates the frequency of matches.
  • Fragments. The service searches for fragments in the text that are present in other texts. This method detects plagiarism even when the word order is changed or the fragment is divided into different paragraphs.

Today, many people actively use neural networks to write texts. Do plagiarism checkers detect AI? As a rule, the standard functionality of such platforms does not allow tracking content created by artificial intelligence. However, many services offer the AI detector as a separate feature or an integrated tool.


Grammarly plagiarism checker is one of the most popular services for checking the uniqueness of English-language content. In addition to detecting plagiarism, it offers a number of complementary tools. With their help, you can generate texts from scratch and improve finished materials. Its algorithms comprehensively analyze content, recognizing grammatical, spelling, stylistic, and punctuation errors.

Best Plagiarism Checkers | Grammarly

Key features:

  • The Plagiarism Detector scans over 15 billion web pages and ProQuest databases of digital versions of magazines, newspapers, scientific articles, and documents.
  • The service compares the text with materials from its database, highlights non-unique proposals, provides a list of resources that are sources of plagiarism, and evaluates overall originality in points.
  • At the same time as checking for plagiarism, Grammarly finds grammatical and stylistic errors in the text and also makes recommendations for improving its quality.
  • You can use the detector through the web interface, mobile application, or extension for Internet browsers Microsoft Edge, Google Chrome, Firefox, Safari.
  • Grammarly's uniqueness check cannot be called 100% accurate. Sometimes it mistakenly considers original content to be plagiarized. This often applies to those texts where there are too many common set expressions and phrases.

Plagiarism checker Grammarly allows you to check texts for free for errors and tone of writing. In addition, it allows you to generate texts using AI without paying, providing a limit of 100 prompts. The range of paid tariffs is represented by 3 plans:

  • Premium (with accidental plagiarism detection feature) – $12 per month.
  • Business (provides a style guide, the ability to work with brand tone and generate texts using AI, analytical functions) – $15 per month for each user.
  • Enterprise (offers a high level of confidentiality, dedicated technical support, and an unlimited number of prompts for text generation) – the cost is calculated individually and is available upon request.

The indicated prices are valid subject to payment for the year immediately. If you pay monthly, the cost will be higher.


Copyleaks is a popular plagiarism checker that also recognizes content generated by artificial intelligence. This allows it to find non-unique texts that have been paraphrased by AI to hide signs of plagiarism.

Top Plagiarism Checkers | Copyleaks

Key features:

  • The AI algorithms used by the service recognize any attempts to disguise plagiarism, including hidden and altered characters, and changes in content by neural networks.
  • Copyleaks finds the slightest evidence of generation in text, including that performed by the latest GPT-4 and Gemini language models.
  • The platform tracks various forms of text paraphrasing, detects text plagiarism scanned from images, and identifies non-unique program code.
  • Copyleaks plagiarism checker collate content against a vast database of 60 trillion sites, over 16,000 journals, over 1 million documents, and more than 20 code repositories.
  • The service finds plagiarism in texts in 100+ languages. Users can send an article in English and find matches in materials in Spanish, German, Chinese, or other languages.

The Copyleaks tariff line consists of 4 plans:

  • AI Content Detector – $7.99 per month.
  • Plagiarism Detector – $8.99 per month.
  • AI + Plagiarism Detection – $13.99 per month.
  • Enterprise and LMS – the cost is calculated individually and is available upon request.

The indicated prices are valid subject to payment for the year immediately. If you choose a monthly payment mode, they will be higher.

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Quetext is one of the popular free online plagiarism checkers. Like other platforms from our selection, it is capable of detecting not only plagiarism but also AI-generated text.

Best Plagiarism Checkers | Quetext

Key features:

  • Thanks to smart DeepSearch algorithms, the platform comprehensively evaluates the originality of content. It takes into account the placement of words, context analysis, and other factors.
  • The ColorGrade system accurately identifies any matches between the text sent to it and content from the internet and the internal database, marking obvious and possible plagiarism with different colors.
  • Users receive links to the matches found so that they can independently examine these texts for plagiarism.
  • Comprehensive scoring of texts for uniqueness and the presence of AI generation in them is provided by an impressive system database containing billions of texts and articles.
  • The service is suitable for checking content in English (6 options), French, Spanish, Italian, German, Portuguese, Polish, Dutch, and Romanian.

Quetext offers three tariff plans:

  • Free (up to 500 words per check).
  • Premium – from $8.8 per month per user.
  • Enterprise – from $8 per month per user.


Scribbr is a reliable representative of universal plagiarism checkers. The platform offers a comprehensive range of tools for enhancing the quality of academic texts. The proofreading function, citation generator, plagiarism and AI generation detectors, as well as its own knowledge base, are particularly impressive.

 Plagiarism Checkers | Scribbr

Key features:

  • The system's algorithms compare the texts sent to it with the content of the internal database. It contains 99 billion web pages and 8 million publications in 20+ languages.
  • Sources include open and restricted access journal articles, dissertations and theses, news reports, PDFs, and web content.
  • The service searches for plagiarism even among unpublished works. Users can upload any texts here and create their own database for verification.
  • Scribbr uses technology from Turnitin, a renowned provider of plagiarism detection systems. Its algorithms track non-unique texts using a number of criteria: from exact word matches to the selection of synonyms.
  • The platform guarantees the confidentiality of personal data. The developers claim that they never add user texts to their content database.

Scribbr cannot be classified as a free plagiarism checker. There is no option to use it for free. This service also does not have tariff plans in the form of a monthly or annual subscription. Payment is charged for checking each text:

  • Small document – $19.95 for checking text up to 7499 words.
  • Regular document – $29.95 for checking text from 7,500 to 49,999 words.
  • Large document – $39.95 for checking text of 50,000 words or more.


Our review ends with the Copyscape detector. Having appeared 20 years ago, it continues to be one of the best plagiarism checkers. The platform provides both free verification of text uniqueness and paid products with advanced capabilities.

Top Plagiarism Checkers | Copyscape

Key features:

  • Web content is checked through a convenient and intuitive interface. Users just need to enter the URL of any site in the window on the main page to find plagiarism of its content on other resources on the internet.
  • Based on the results of the check, the platform provides a list of web pages on which matches were found. When following links, users will see non-unique fragments highlighted in color.
  • Copyscape Premium detects plagiarism not only on web pages but also in individual text fragments and files (DOC, PDF). Purchasing a paid subscription frees users from restrictions on the number of checks.
  • Among the additional features of the Premium version, batch checking, private indexing, case tracking, integration with WordPress and API are especially attractive.
  • The built-in Siteliner tool tracks duplicate text within a single site of up to 25,000 pages.
  • The Copysentry solution protects websites from content theft by regularly monitoring the internet for plagiarism. When copied materials are detected on other sites, the user receives an email notification.

The cost of a paid Copyscape Premium review is $0.03 for the first 200 words and $0.01 for every 100 words over this limit.


We hope our article helped you find the answer to the question "What are the best free plagiarism checkers?" The services discussed in it are quite accurate and provide useful additional tools (for example, recognition of AI-generated texts). Almost all plagiarism detectors offer a free plan, which is convenient for those who only use them occasionally. Paid plans for the systems in our selection have a wide price range: from $0.01 per 100 words (Copyscape) and $8 per month per user (Copyleaks, Quetext) to $39.95 for checking one text (Scribbr).


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