Best Free Plagiarism Checkers | Tested & Reviewed

To find the best free plagiarism checker, we extensively tested and reviewed all popular tools to answer questions like, “How much plagiarism can they detect?” and “Are they actually free?”

Research methodology

The plagiarism tools in this research were tested using four test documents, ranging from unedited to heavily edited.

Each test document consisted of plagiarized sections from 140 sources like Wikipedia articles, news articles, open-access journal articles, websites, theses and dissertations, and PDFs.

This setup allowed us to analyze:

• The reliability of plagiarism checker tools, even when texts are edited to varying degrees
• The depth and breadth of the tools’ content databases (whether they cover only websites or also journal articles)

Read more about the research methodology

General conclusions: Free vs. paid checkers

We found that free tools were frequently misleading in their advertising and were lacking in many ways compared to paid ones. Our research led to these conclusions:

1. Scribbr review

Pros

• Offers a limited free version
• Finds far more plagiarism than other tools
• Detects plagiarism even in edited texts
• Won’t store or sell your documents
• Money-back happiness guarantee, with live support available
• Self-Plagiarism Checker feature allows you to check for self-plagiarism

Cons

• You need to go premium to find out your precise similarity score and view the entire report

Free?

Scribbr offers a limited free version that’s perfect for checking if your paper contains potential plagiarism. To view the full report, you need to buy the premium version, which costs between $19.95 and $39.95 depending on the word count. There’s no word limit, so you can upload as big a document as you want.

Quality of matches

Scribbr’s checker, developed in partnership with Turnitin, heavily outperformed all free and paid tools in terms of the amount of plagiarism detected: 88% vs. an average of 43% across free tools.

It performed particularly well with source types relevant to students, such as journal articles and dissertations. Importantly, Scribbr was far more successful than other tools at detecting plagiarism in heavily edited texts, showing it has no trouble with paraphrasing plagiarism.

Scribbr could also consistently provide full matches instead of partial ones, matching the whole plagiarized passage to the correct source.

Usability

You see your results in a straightforward downloadable report. Different sources are highlighted in different colors, making it more readable.

The issues identified can be fixed with Scribbr’s Citation Generator, generating correctly formatted citations wherever they are needed.

In addition, Scribbr offers a Self-Plagiarism Checker. This unique tool allows users to upload their own unpublished documents in addition to the public database to detect any possible self-plagiarism.

However, you can’t edit your text directly in the tool, and it’s not possible to recheck your document for free.

Trustworthiness

Scribbr will not store, sell, or share your uploaded documents. Data is automatically deleted after 30 days, or students can opt to manually delete their document after the check.

Live customer support is offered in multiple languages to assist users. A guide and other resources explaining plagiarism issues are easily accessible.

Scribbr also has a happiness guarantee: if you’re not satisfied with the tool for any reason, you can ask for a new check or a refund.

Check out Scribbr

2. PlagAware review

Pros

• Online report is color-coded
• Detects more plagiarism than other tools (aside from Scribbr)
• Won’t store or sell your documents

Cons

• Only a one-time free trial before you must pay
• Difficult to read PDF reports
• Does not work well for scholarly sources

Free?

PlagAware offers a one-time trial of 10 credits (10 pages). To get the results of this trial, you must sign up for an account.

If you want to run additional scans, you must buy additional credits (beginning at 100 credits for $15). 

Quality of matches

PlagAware often correctly attributed plagiarized text and was able to find some full matches. It identified an average of 57% of the plagiarized material across all sources, which is the second-highest average after Scribbr (88%). 

It did not perform very well with heavily edited texts or in finding plagiarized material in scholarly sources, though. 

Usability

The website report is easy to interpret since it uses different colors for different sources and gives a similarity percentage for each plagiarized section. The tool also has a dashboard with a history of your scans, which is useful. However, the formatting of the original document is not preserved. 

The downloadable report is confusing, though, because it only uses one color for all sources.

Trustworthiness

According to PlagAware’s website, users can delete documents from their profile at any point. There is a contact form and phone number but no live online support. 

Check out PlagAware

3. Prepostseo review

Pros

• Color-coded highlighting for different types of plagiarism
• Some full matches
• Citation assistant

Cons

• Detects a low proportion of plagiarism
• Downloadable report is hard to read
• Color coding doesn’t distinguish between different sources

Free?

With the free version of Prepostseo, users can scan up to 1,000 words at a time and can perform 30 search queries per month (one search query = one sentence), according to Prepostseo’s website. During our testing, the search query limit did not seem to apply, though. 

The cheapest monthly plan ($10/month) allows up to 5,000 words per search and 5,000 search queries. 

Quality of matches

Prepostseo did find the occasional full match, but in most cases it was only able to find partial matches, like most free checkers. It generally attributed plagiarized text to the correct source and performed fairly consistently across all levels of editing. 

Usability

Different colors are used for verbatim plagiarism and paraphrasing plagiarism, but the tool’s judgment about this was often wrong. Other than that, the same color is used for different sources, which makes the report hard to read. The PDF report does not indicate which portion of text is from which source. 

The site offers tools to eliminate plagiarism, but they did not always function well. 

Trustworthiness

Prepostseo states that it does not store or sell your documents. There is a form you can use to request support but no live support option. 

Check out Prepostseo

4. Grammarly review

Pros

• Language and citation assistant available
• Does not sell or share documents with third parties

Cons

• Free report gives very minimal information
• Finds a relatively low percentage of plagiarism
• Same colors used for different sources

Free?

The plagiarism checker is not included in Grammarly’s free plan. All you can see is a screen that tells you there’s plagiarism in your text without giving you any details of where it is, how much of it there is, or what the sources are.

After this, you’re directed to subscribe to Grammarly’s premium service ($12 per month). There’s a limit of 100,000 characters (about 20,000 words) per document even after paying.

Quality of matches

Grammarly found a relatively low amount of plagiarism. It scored lower than 40%, even with unedited texts. 

When it did find plagiarism, it was often only a partial match rather than a full one.

Usability

As a premium service, Grammarly has a clearer and more visually appealing style than most free checkers. The original formatting of the document remains mostly intact, but the tool uses the same color for all sources, making the results hard to parse. Additionally, you have to divide longer texts into multiple parts in order to run the scan. 

The subscription also gets you a language and style tool and a citation assistant.

Trustworthiness

Grammarly does not store, sell, or share documents with third parties.

The site provides a support page with tips, tutorials, and FAQs, and you can submit a question via a form. Live support is not available.

Check out Grammarly

5. DupliChecker review

Pros

• Free (1,000 words per scan)
• Doesn’t save uploaded documents
• Relatively user-friendly reports

Cons

• Distracting ads for other services
• Low level of plagiarism detected
• Only able to find partial matches
• No color coding for different sources

Free?

DupliChecker’s service is free, though you can only upload 1,000 words at a time. If you go for one of their premium plans, you can go up to 25,000.

If you do want to upgrade, a large number of different premium plans are offered on the site, which can be somewhat confusing to navigate. The cheapest is $10 a month.

Quality of matches

DupliChecker was able to identify more than 40% of the plagiarized material, even for edited texts, but it was unable to find any full matches. When entire sentences were plagiarized, it often only marked part of the sentence. 

Usability

The webpage is cluttered with ads, and it is difficult to know what button to press to run the plagiarism check. In both the online and downloadable reports, all plagiarized text is highlighted in one color, and it is difficult to figure out what source each source block is matched with.

Trustworthiness

The site claims not to save uploaded documents, and it deletes content after the check is complete to avoid data leakage. No live support is available, but there is a contact form on the website.

Check out DupliChecker

6. Check-Plagiarism review

Pros

• 1,000-word upload limit
• Online report clearly matches plagiarized content with source

Cons

• Difficult to match text with sources in the downloadable report
• Different sources highlighted in the same color
• Scans sentence by sentence—rarely gets a full match
• Site has a lot of ads that interfere with usability

Free?

Check-Plagiarism is free for scans of up to 1,000 words. Their site says that guests are limited to 50 search queries/month (one sentence = one query). However, it was not clear that this limit was enforced during our testing. A weekly plan ($6.99/week) increases this limit to 10,000 words, and a monthly plan ($17/month) increases it to 35,000 words.

Quality of matches

Check-Plagiarism found a low percentage of plagiarism, scoring an average of 37%. It performed particularly poorly for scholarly sources and sources that had been edited.

While the tool was able to find some full matches, it mostly found partial matches.

Usability

The downloadable report provides a long list of sources that are difficult to cross-reference with the text above.

The version of the report shown on the site itself is slightly better, as a box next to the plagiarized text allows you to see the text identified as the source. The site itself is quite cluttered with ads, though. There is a “rewrite” function (which only replaces words and will not eliminate plagiarism), along with a manual citation tool.

Trustworthiness

Check-Plagiarism says that documents are not saved or shared with third parties. 

There are some FAQs listed on the site, but the answers provided are not very clear. There is a contact form but no live support.

Check out Check-Plagiarism

7. Copyleaks review 

Pros

• Formatting is preserved in the online tool
• Online report clearly matches plagiarized content with source

Cons

• Only one free trial available
• Difficult to match text with sources in the downloadable report
• Performs poorly with academic sources
• Unclear data protection policy

Free?

Copyleaks offers one trial of 2,500 words. To get the results of this trial, you must sign up for an account. 

After the trial, you must sign up for a subscription plan to run more scans. Monthly subscriptions start at $16.99/month for 100 credits (1 credit = 250 words). Annual subscriptions start at $13.99/month for 1200 credits.

Quality of matches

Copyleaks performed poorly with all source types, finding an average of only 38% of the plagiarized text. It was sometimes able to attribute an entire source block to the correct source but mainly found only partial matches.

Usability

The downloadable report lists all sources at the top, and it is impossible to cross-reference them with the text below. 

The online report is slightly easier to read. However, since it checks sentence-by-sentence, you have to click each sentence of a paragraph to see the source. The tool distinguishes between text that is “identical,” has “minor changes,” or is “paraphrased,” but its judgment is often wrong. 

Trustworthiness

Copyleaks says that they “will never steal your work.” However, users have to contact customer service to permanently remove their files. The website has a contact form and a chat option.

Check out Copyleaks

8. Small SEO Tools review

Pros

• Free (1,000 words per scan)
• Various options for document uploads
• Documents not stored in database

Cons

• Low level of plagiarism detected
• Page is slow and somewhat confusing
• Scans individual sentences rather than full texts

Free?

Small SEO Tools is free to use, although you can only check 1,000 words at a time without paying.

You can run multiple checks if you need to scan more than that, although the site requires you to complete CAPTCHAs to upload multiple documents.

Quality of matches

Small SEO Tools was unable to identify most plagiarism in our test documents, with an average of only 44%. Since it scans individual sentences separately, it was only ever able to produce partial matches.

Additionally, when a scan was run multiple times, the percentage of plagiarism changed, indicating unreliability.

Usability

While the page is cluttered with ads, the online report itself is relatively clear. The tool clearly links matched text with the source identified for it, but only one color is used to match each source. 

Small SEO Tools offers a link to an AI paraphraser with the button “Remove Plagiarism.” However, the paraphraser only changes certain words, which does not eliminate plagiarism in a document. 

The PDF report is very difficult to read because the formatting of the original document is not preserved. Additionally, there are no clear links from the text to sources.

Trustworthiness

Small SEO Tools states that user files are deleted once the scan is run. You don’t have to register to use the tool. The website has a contact form but no other form of support.

Check out Small SEO Tools

9. Plagiarism Detector review

Pros

• Free to use (1,000-word limit)
• Does not store or sell your document

Cons

• Technical issues with long documents
• Difficult to match text with sources in the report
• Different sources highlighted in the same color

Free?

Plagiarism Detector is free to use, and users do not need to register. However, there is a limit of 1,000 words per document. By paying, you can raise this limit to 25,000 words per document.

Quality of matches

Plagiarism Detector found only 35% of the total plagiarized content. It performed particularly poorly for scholarly sources and heavily edited texts. 

The tool was mostly only able to find partial matches, attributing individual sentences to one or more sources.

Usability

Plagiarism Detector’s downloadable reports are somewhat difficult to read. The same colors are used for different sources, and hovering over a plagiarized section doesn’t show you the source. Instead, you need to find it in a separate list.

The online report is somewhat better. Even though only one color is used, you can click on a sentence to be shown the source. However, the formatting of the original document is not preserved, which makes it difficult to read. 

Trustworthiness

Plagiarism Detector states that it will not store or sell your documents. No live support is available, but there is a help request form.

Check out Plagiarism Detector

10. Quetext review

Pros

• Built-in citation assistant helps to add missing citations
• Documents not stored in database
• Support options available (but no live support)

Cons

• Finds partial matches
• Monthly subscription of at least $7.20 after free trial
• Not effective for scholarly sources

Free?

Quetext offers a free trial of 500 words, after which users must pay for a premium plan.

The paid version costs at least $7.20 per month (more expensive plans are available), which allows you to check up to 100,000 words.

Quality of matches

Quetext detected 48% of the plagiarized material, but it was unable to match each source text fully to a single source. Different sentences were attributed to different sources.

The tool also sometimes attributed plagiarized material to an incorrect source.

Usability

Both the online report and the downloadable report completely change the formatting of the text, making it difficult to read. Additionally, different sources are not highlighted in different colors. Instead, orange highlighting is used for partial matches and red for full matches, but it is difficult to tell what material comes from what source.

There’s a built-in citation assistant that can help you fix plagiarism by adding citations. Unfortunately, it’s not very robust. Citations generated this way may not be accurate, and you have to add a lot of information manually.

Trustworthiness

Quetext states that it doesn’t save your text to a database and that all text submitted remains private and encrypted.

Information about the service is available in the form of FAQs on the website, and it’s also possible to contact the company by submitting a request form.

Check out Quetext

11. Smodin review

Pros

• Site has a citation generator
• Documents not stored in database
• Support options available (but no live support)

Cons

• Can only scan 1,500 characters
• Finds very low percentage of plagiarism
• Does not find full matches
• Report is difficult to read

Free?

Smodin is free, but you can only scan 1,500 characters (not words) at a time on the free plan. The paid version costs $12/month but only allows up to 12,000 characters/scan, the lowest limit of any tool we tested.

Quality of matches

Smodin performed very poorly in all rounds of testing, finding on average only 16% of the plagiarized text. It performed particularly poorly with edited texts. It often did not find even partial matches.

Usability

The tool has a very low limit of 12,000 characters (not words) per scan, even with the paid version.

Both the online report and the downloadable report are very difficult to read. The downloadable report displays all the text that it deems plagiarized at the bottom of the page rather than highlighting it in the body of the text itself.

Trustworthiness

According to their website, Smodin does not save documents or share them with third parties. There is a help page and contact form but no live support option.

Check out Smodin

Frequently asked questions about plagiarism checkers

Can you use Turnitin for free?

Yes, Scribbr offers a limited free version of its plagiarism checker in partnership with Turnitin. It uses Turnitin’s industry-leading plagiarism detection technology and has access to most content databases.

Run a free plagiarism check

If you’re a university representative, you can contact the sales department of Turnitin.

How is plagiarism detected?

Plagiarism can be detected by your professor or readers if the tone, formatting, or style of your text is different in different parts of your paper, or if they’re familiar with the plagiarized source.

Many universities also use plagiarism detection software like Turnitin’s, which compares your text to a large database of other sources, flagging any similarities that come up.

It can be easier than you think to commit plagiarism by accident. Consider using a plagiarism checker prior to submitting your paper to ensure you haven’t missed any citations.

Are plagiarism checkers accurate?

The accuracy depends on the plagiarism checker you use. Per our in-depth research, Scribbr is the most accurate plagiarism checker. Many free plagiarism checkers fail to detect all plagiarism or falsely flag text as plagiarism.

Plagiarism checkers work by using advanced database software to scan for matches between your text and existing texts. Their accuracy is determined by two factors: the algorithm (which recognizes the plagiarism) and the size of the database (with which your document is compared).

To which databases will my document be compared?

Your document will be compared to the world’s largest and fastest-growing content database, containing over:

• 99.3 billion current and historical webpages.
• 8 million publications from more than 1,700 publishers such as Springer, IEEE, Elsevier, Wiley-Blackwell, and Taylor & Francis.

Note: Scribbr does not have access to Turnitin’s global database with student papers. Only your university can add and compare submissions to this database.