5 best free plagiarism detectors and the latest guide on how to use them

plagiarism detector
Plagiarism is a serious academic offence — and knowing the ins and outs of using a plagiarism detector is a great way to avoid plagiarism. Source: Brandon Bell/Getty Images North America/ Getty Images/AFP

Not every plagiarism detector online is created equal. It’s important to know each well before using one.

Trust the wrong plagiarism detector and you could find yourself facing some major consequences. 

Hong Kong Baptist University students could have their grades reduced or fail courses if they were caught taking words or ideas from other sources, including ChatGPT and other AI technologies, without proper citation.

The same applies to many universities elsewhere. Failing classes almost always leads to getting suspended or expelled from your uni — affecting your international student visa.

According to Monash University’s website, the uni reports any case of suspension and expulsion to the Department of Education, which may result in the cancellation of a study visa. 

At the University of Bath, students will be told to return to their home country if they are suspended from their studies.

Plagiarism can also leave you red in the face. One student was accused of plagiarism after giving a speech at Duke University’s commencement ceremony.

The Chronicle — Duke University’s student-run news organisation — reported that Priya Parkash’s speech was similar to student Sarah Abushaar’s 2014 Harvard University commencement speech.

The international student from Pakistan released a statement: “When I was asked to give the commencement speech, I was thrilled by such an honour and I sought advice from respected friends and family about topics I might address. I was embarrassed and confused to find out too late that some of the suggested passages were taken from a recent commencement speech at another university.”

Knowing which plagiarism detector online to use and how they work can help you avoid these situations. 

How do plagiarism detectors work?

A plagiarism detector relies on advanced database software to scan for matches between your text and existing texts. At uni, they are used to scan student assignments.

Some plagiarism detector can search through content on the web and scans your text for similarities against a database of existing content on the Internet.

Some can even identify non-exact matches (paraphrasing plagiarism).

When using these tools, you’ll usually see a plagiarism percentage and a report highlighting plagiarism (if any), and a list of your sources.

plagiarism detector

Ideas that have been rewritten or translated cannot be detected by a plagiarism detector. Source: Brandon Bell/Getty Images North America/Getty Images/AFP

Plagiarism detector: Accuracy and mistakes to avoid when using

There are a few factors that can affect the accuracy of a plagiarism detector. It involves:

  • The way a specific plagiarism detector works
  • External factors 

Database size 

Not every plagiarism detector operates with a similar database. These differences can significantly affect the results. 

Smaller databases, for example, will have large gaps in their ability to find matches, especially content that is not easily accessible online. 

Scribbr’s plagiarism detector, on the other hand, has access to Turnitin’s comprehensive database.

In addition to web sources, its database also contains scientific publications, scholarly journals, and books.

Scanning quality 

Many free plagiarism detectors only recognise exact matches. If you paraphrased too closely or forgot to add a citation, these checkers will unlikely flag it.

Premium plagiarism detectors use “fingerprinting,” a process that identifies non-exact matches among paraphrased or altered texts. The software scans sentence fragments, searching for structural similarities.

Like real fingerprints, each fragment in your text should be unique and shouldn’t match existing document fingerprints. 

plagiarism detector

Plagiarism of images cannot be detected by conventional plagiarism detectors. Source: Adrian Dennis/AFP

Ideas and non-text plagiarism 

Plagiarism detectors cannot scan for ideas that have been rewritten or translated — which also counts as plagiarism if not cited properly. They also do not detect non-text plagiarism, such as plagiarism of images. 

Text from internal databases

On top of standard plagiarism detectors, most unis have their internal database containing previous work from current and former students. 

Usually, this database isn’t shared with outside parties. Here’s where things get tricky: plagiarism from fellow students will likely only be recognised by your uni and not by a commercial plagiarism detector. 

plagiarism detector

Paraphrasing does count as plagiarism. Source: Brandon Bell/Getty Images North America/Getty Images/AFP

Does paraphrasing count as plagiarism?

Say you are summarising an article or another source. 

In that case, you should follow two rules: write the summary in your own words by paraphrasing the author’s ideas or cite the source with an in-text citation and a full reference for your readers to easily find the original text.

Mastering the common citation styles at uni will help a lot.

The two most common citation styles at university are the MLA (Modern Language Association) and APA (American Psychological Association) formats.

If you’re unsure which to use, find out from your professor.

plagiarism detector

The best plagiarism detector can help you minimise the chances of plagiarism in your uni assignments. Source: Justin Sullivan/Getty Images North America/Getty Images/AFP

Best plagiarism detectors for university students


It is typically used to spot grammar mistakes, but did you know Grammarly also has a plagiarism detector?

Just copy a passage or upload a file to check your work against ProQuest databases and 16 billion web pages.

You will also gain useful insights into punctuation, vocabulary, and sentence structure to improve your work.


Tap into this free plagiarism detector’s DeepSearch technology for contextual analysis on any subject matter.

Quetext promises fast, accurate scanning while protecting the privacy of its users. Feedback includes colour-grading text based on the level of plagiarism and a comprehensive plagiarism score.


If you’re familiar with Turnitin, you can place your confidence in EasyBib — which claims to use similar technology.

Beyond checking for plagiarism, this software provides suggestions to improve your grammar and style.

Bonus: You may submit your paper for a 24-hour in-depth check, which involves detailed feedback from writing experts.


Unicheck compares your work against over 91 billion web sources and open-access databases, so you can be sure it catches everything.

Students will find the full-scale interactive report helpful; you can check similar sources and adjust citations and references.

With its in-depth explanations and promise of 99% uptime, it’s no wonder this software is used by students and teachers alike. Even universities use it to check assessments.


Another plagiarism checker that uses DeepSearch technology is Duplichecker, which offers a basic free version and a multifunctional pro version.

Your results will show percentages of plagiarism, unique, and related-meaning sentences.

To begin, copy texts of under 1,000 words or upload your document.


Plagium is a user-friendly tool for plagiarism detectors for detecting content in text and URLs. 

Its unique approach breaks down your text into snippets, providing cleaner and less cluttered search results compared to its counterparts. 

What’s more impressive is its ability to pinpoint the source URL of plagiarised content accurately. 

With a straightforward text box accommodating up to 1,000 characters, Plagium offers quick and deep search options. 

Plagium offers paid plans for the budget-conscious student based on the number of pages searched.

plagiarism detector

With the rise of ChatGPT, some experts predict that it will be harder to detect plagiarism because of the ability of chatbots to craft “unique and almost individualised content.” Source: Olivier Douliery/AFP

Which plagiarism detectors online can spot ChatGPT use?

ChatGPT and plagiarism — these two words are coming together more often recently.

The chatbot powered by artificial intelligence (AI) sounded alarm bells in education circles when it threatened to upend the authenticity of student essays.

While a plagiarism checker might not definitively determine whether a language model was used to generate a piece of text, it can help you identify instances of copying or paraphrasing from other sources.

At the time of writing, it can still be hard to detect plagiarism by an AI chatbot.

That’s because AI writing tools use natural language and grammar to craft “unique and almost individualised content,” even if the content is drawn from a database, according to Aaron Leong from Digital Trends.

Still, it didn’t stop Turnitin, a popular free plagiarism checker used by educators and students worldwide from releasing new features to detect the use of AI writing tools.

According to the provider, these features can be found in Turnitin Feedback Studio (TFS), TFS with Originality, Turnitin Originality, Turnitin Similarity, Simcheck, Originality Check, and Originality Check+.

Currently, the new features on this platform have reportedly been able to detect the presence of AI writing with 98% confidence and a less than one percent false-positive rate in Turnitin’s controlled lab environment.

The risk of using ChatGPT in university 

You may be penalised for plagiarism if you use AI tools like ChatGPT to write your university assignments. 

When you rely on AI to complete your assignments without proper attribution or understanding, you could get yourself in some trouble.

Many universities have strict policies against plagiarism, and using AI-generated content falls into this category. 

“ChatGPT’s unauthorised use, like that of other chatbots or artificial intelligence software, would be considered a form of cheating under our assessment regulations,” shared a spokesperson from the University of Bristol

There is no denying the allure of using AI to complete your work. It is efficient and saves you the hours needed to complete your assignment.

It’s not just failing a grade. You could risk being expelled, which could lead to you losing your student visa and jeopardising your future.

So how can you use AI tools in university without crossing any ethical lines?

Here are some tips:

  • You could use it to summarise long articles to read them easily
  • You could use it to ask for research guidance
  • It can be used to proofread your work
  • Use it as a spelling and grammar checker