Best Plagiarism Checkers for Students and Writers

You run a plagiarism check to find out whether your essay, paper or blog post matches someone else’s work before you submit or publish it. The trouble is that the score on its own can mislead you. A clean 0% can miss a source the checker never searched, and a 20% report can be nothing more than quotations you’ve already cited properly.

So the best plagiarism checkers are the ones that search the sources your writing is likely to match and show you every matching passage next to its source. Which one fits depends on what you’re checking.

For blog posts and client articles, I’d use Copyscape Premium. It checks unpublished text against the web for 3 cents a search, with no subscription.

If you’re writing an essay, thesis or research paper, check what your college already gives you first, because Turnitin access comes through the institution. If it gives you nothing for drafts, Scribbr sells a full report per document.

Quetext is the free option for shorter text, at up to 1,000 words a check. Grammarly, Copyleaks and ProWritingAid make sense when you already pay for them or need something the first three don’t do.

Quick Comparison

Find what you’re checking in the Best For column, then jump to that tool’s entry below.

Tool	Best For	Free Option	Paid Price	Main Limit
Copyscape	Blog drafts and published pages	URL search for published pages	$0.03 per search up to 200 words, $0.01 per extra 100 words	Searches the web, not private student papers
Quetext	Short essays and articles	Up to 1,000 words per check	Plagiarism-only plan from $5.49/month billed yearly	Free checks stop at 1,000 words
Scribbr	An occasional thesis or research paper	Risk rating and top sources	$19.95 to $39.95 per document, by length	Can’t search your university’s private archive
Grammarly	Writers who already pay for Grammarly	Tells you whether matches exist	Pro at $12/month billed yearly	100,000 characters per check, no PDFs
Copyleaks	Regular checks with AI detection	A few free credits for new accounts	$13.99/month billed yearly	100 credits a month, 1 credit per 250 words
ProWritingAid	Authors who already use ProWritingAid	None	10 checks for $10	Each check covers up to 2,000 words

Best Plagiarism Checkers

I picked these 6 for what they search, what they cost and the job each one does best. They aren’t ranked by accuracy. A fair accuracy ranking needs the same test documents run through every tool with the same settings, and the benchmark charts you’ll find on vendor pages are run by the vendors themselves.

Copyscape

Copyscape is my pick for anyone who publishes on the web: bloggers, editors and agencies checking a writer’s draft before it goes live. It comes in two parts that do different jobs.

• The free search at copyscape.com takes the URL of a published page and finds other pages carrying similar text. That’s how you find out who copied your article.
• Copyscape Premium takes pasted text or an uploaded PDF or Word file, so you can check a draft before anyone else sees it.

Premium is pay per search, with no subscription:

• 3 cents for a search of up to 200 words
• 1 cent for every extra 100 words, or part of it
• 11 cents for a 1,000-word draft

Premium also lets you build a private index of your own content to check new drafts against, and Batch Search checks up to 10,000 pages in one go. Copyscape sells an AI detector as well. Its AI probability score answers a different question from the plagiarism matches, so I’d read the two separately.

The limit is what Copyscape searches. It looks at the web, so it won’t see a classmate’s paper sitting in a university’s archive, a paywalled journal or a book that isn’t online. That hardly matters for blog content, but for academic work it’s a real gap.

Quetext

Quetext is the free plagiarism checker I’d point a student or writer to for a quick first check. You paste up to 1,000 words, and the report highlights matching text and links each match to its source.

Here’s what you get:

• DeepSearch compares your text with web pages, journals and academic publications, and ColorGrade color-codes exact matches and near matches.
• The Citation Assistant builds APA, MLA and Chicago citations for the sources it finds, even on the free plan.
• Uploads take Word, PDF and plain-text files, and a PDF needs selectable text.
• The Plagiarism Checker Only plan costs $9.99 a month, or $5.49 a month billed yearly, for 50,000 words a month.
• Essential adds the AI detector and 100,000 words a month for $14.99 a month, or $8.25 a month billed yearly.

The free version is fine for a short essay or a section of a longer one. A 4,000-word paper has to go in 4 pieces, and the paid plan is the better deal once you’re checking that much every month. Like every individual checker, Quetext can’t search your university’s private archive of submitted papers, so its score won’t match the report your instructor sees.

Scribbr

Scribbr is the one I’d use for a thesis, dissertation or research paper when your university doesn’t give you a way to check drafts. It sells a full report per document and compares your paper with a database of 99.3 billion web pages and 8 million publications from more than 1,700 publishers.

Prices are per check, not a subscription:

• $19.95 for up to 7,499 words
• $29.95 for 7,500 to 49,999 words
• $39.95 for 50,000 words or more

The free version gives you a plagiarism risk rating and the top matching sources. The paid report adds the exact similarity percentage, the full source list, a side-by-side comparison with each source and an AI percentage.

Pay per document suits the student who checks one big paper a semester. If you write a lot of shorter essays, a monthly plan such as Quetext costs less per check. Scribbr also says plainly that its result can differ from your university’s, because it can’t search the private archive of papers submitted to your institution.

Grammarly

Grammarly’s plagiarism check makes sense if you already pay for Grammarly Pro for its writing feedback. The paid check compares your text with billions of web pages and ProQuest’s academic databases, flags the sentences that match and shows a source for each one. The free checker on Grammarly’s site only tells you whether duplicate content exists.

The plan details that matter for plagiarism checking:

• Pro costs $12 a month billed yearly ($144), or $30 month to month.
• In India, Grammarly sells a Plus plan instead, at ₹392 a month billed yearly or ₹1,000 month to month, and it includes the plagiarism check.
• Each check takes up to 100,000 characters. Uploads have to be Word, OpenDocument, text or RTF files of 4 MB or less, so PDFs are out.
• Every account can check up to 150,000 words or 300 documents in 30 days.

I wouldn’t buy Grammarly only for plagiarism checks. You’re paying for grammar, tone and rewriting help, and the plagiarism check comes along with it. If that’s useful to you anyway, my Grammarly review covers the rest of the plan. If it isn’t, my list of Grammarly alternatives has cheaper editors.

Copyleaks

Copyleaks is for regular checking when you also want AI detection, because one scan checks for copied text and AI-written text in the same report. Plagiarism detection covers more than 100 languages and AI detection covers 30+, which helps if you write or review content outside English.

The pricing runs on credits:

• Personal costs $16.99 a month, or $13.99 a month billed yearly ($167.88).
• The monthly plan gives you 100 credits, and 1 credit covers up to 250 words, so that’s about 25,000 words a month. Unused monthly credits don’t roll over.
• The yearly plan loads all 1,200 credits upfront, to use within 12 months.
• New accounts get a small number of free credits to try it.

Its Text Compare tool is worth knowing even if you don’t subscribe. You paste two documents and it highlights the passages they share, which helps when you suspect one specific article was copied from another and a web search doesn’t show the link.

ProWritingAid

ProWritingAid sells plagiarism checks separately from its writing plans, so you can buy a few without a subscription. They come in packs, work in a free account and never expire:

• 10 checks for $10
• 100 checks for $40
• 500 checks for $120
• 1,000 checks for $200

Where you write matters too:

• The check works in the web editor, the Word add-in for Windows and Google Docs.
• It doesn’t work in the Word add-in for Mac, Desktop Everywhere or the browser extensions.

The catch is document size. Each check covers up to 2,000 words, so an 8,000-word manuscript uses 4 checks and a short passage still uses a whole one. For an author who checks a chapter now and then, the credits are cheap. For a full book, do the math before you buy a pack. My ProWritingAid review covers the editing side.

Free Plagiarism Checkers

A free plagiarism checker is useful for a first look. Just know which kind of free you’re getting, because it usually means one of these:

• a URL search that only works for pages already published, like free Copyscape
• a capped text box, like Quetext’s 1,000 words
• a teaser that tells you matches exist and asks you to upgrade to see them

DupliChecker takes 10,000 characters per search, roughly 1,500 words, and a basic check doesn’t need an account. Paid plans start at $9.99 a month.

Plagiarism Detector checks 1,000 words at a time for free. Its Basic plan costs $9.99 a month for 36,000 words, or $53.88 a year.

QuillBot’s plagiarism checker isn’t part of its free plan. It comes with QuillBot Premium, which includes 25,000 words of plagiarism checks a month.

I’d use these for a quick screen of a blog post. For a graded paper or a client deliverable, I’d want a report from one of the tools above, because the free tiers don’t say much about which sources they search.

Plagiarism Checks for Students and Researchers

The best plagiarism checker for students is usually the one their instructor already uses, and that’s often Turnitin. Turnitin doesn’t sell accounts to individual students. You get access through your school or university, either as a draft assignment your instructor sets up before the final submission or through Turnitin Draft Coach, if your institution has switched it on.

Turnitin’s media kit lists 3 kinds of sources it compares a paper against:

• more than 91 billion web pages
• more than 1.9 billion student papers
• more than 190 million journal articles

The student papers are the part no individual checker can reach.

That archive is the reason a web checker and Turnitin can disagree. A paragraph borrowed from a senior’s old assignment won’t show up on Copyscape or Quetext, because the source was never on the open web. Turnitin’s assignment settings can store a new submission in the general Turnitin repository, in a private institutional repository or not at all, so two reports for the same paper can differ by settings alone.

Before you pay for another service, ask whether your course has a draft submission or a practice assignment. It’s free, and it’s the closest you’ll get to the report your instructor sees.

Researchers preparing a journal manuscript should follow the journal’s own process first. If you need to check a manuscript yourself, Turnitin points individuals to iThenticate, which sells single checks: $125 for 1 manuscript of up to 25,000 words, or $300 for up to 3 manuscripts. Those credits last 12 months and don’t include AI writing detection.

Unicheck, which some schools used instead of Turnitin, stopped running on January 1, 2025. Its old links now lead to Turnitin.

If you’re still writing the paper, my guide to dissertation writing covers structure and sourcing before you get to the checking stage.

How to Read a Similarity Report

A similarity report shows how much of your text matches the sources the checker searched, and links each match to its source. I want to ensure you read it properly, because the percentage at the top is the least useful part of it.

Open the matches before you trust the percentage.

Here’s the order I’d work through a report in:

1. Open the source behind each big match. Check whether it’s the original work, a quotation you used or just another copy of the same text.
2. Read the matching passage. A distinctive paragraph needs a closer look than a common phrase, a title or a line from your reference list.
3. Check the credit. Exact wording needs quotation marks and a citation, and an idea you paraphrased still needs a citation. My guide to citations covers the formats.
4. Set the quotation and bibliography exclusions to match your assignment or editorial rules. Keep the same settings when you compare two reports.
5. Fix the writing or the credit, then check the changed passage again. Swapping words to push the score down doesn’t fix a missing source.

Take two 800-word drafts as an example. One has 160 words of properly quoted and cited material, which shows as 20% similarity. The other has 32 words copied into a paragraph with no citation, which shows as 4%. The 4% draft is the one that needs fixing before it goes anywhere. The 20% draft only needs a check on how much quoting the assignment allows.

There’s no universal acceptable percentage either. Turnitin itself says there’s no single acceptable or perfect similarity score, and that a person always has to review the report. Your institution’s rules and the matches themselves decide what needs fixing.

Plagiarism Checker vs AI Detector

A plagiarism checker looks for text that matches existing sources. An AI detector estimates whether writing has patterns common in machine-generated text. Some tools, including Copyleaks and Grammarly, offer both, but the two results answer different questions.

AI-written text can still contain copied or closely paraphrased material, so it can still match a source. And neither result settles authorship on its own. Turnitin’s guidance says its AI writing score shouldn’t be the sole basis for action against a student. If you need to judge that separately, my comparison of AI content detectors covers which ones hold up and where they fail.

Duplicate Content on Your Website

If you run a website, the plagiarism question usually comes in two forms: someone copied your article, or the same text shows up on several of your own pages. These need different tools.

• For copies of your published pages on other sites, the free Copyscape URL search is the quick check. If you’d rather have it watch your pages for you, Copysentry checks up to 10 pages weekly for $4.95 a month, or daily for $19.95 a month.
• For repeated text across your own site, Copyscape’s sister tool Siteliner scans up to 250 pages for free once every 30 days. Its Premium version costs 1 cent per page scanned.

A plagiarism score doesn’t predict a ranking drop. Google’s documentation says some duplicate content on a site is normal and isn’t a violation of its spam policies. Copying other sites’ content and republishing it without adding anything is a different case, which Google’s spam policies treat as scraping. Repeated text across your own URLs usually needs a canonical tag, a redirect or a merge, and my guide on how to prevent duplicate content covers those fixes.

Document Privacy

Before you upload an unpublished thesis, client work or anything under an NDA, check what the service does with it. Three separate things matter here:

• Storage: whether the service keeps your file after the check, and for how long.
• Indexing: whether your text is added to a database that future submissions are checked against. This is what causes a self-match later.
• Training: whether your text can be used to improve the company’s products, including AI models.

Scribbr, for example, says your submissions will never be added to its content database and lets you delete your document right after the report. Its terms still allow it to keep a paid check in a private database only Scribbr can access. Both can be true at once, which is why I’d read the terms and not just the landing page. At school, your instructor’s Turnitin assignment settings decide whether your paper joins the archive.

I’d be careful with free checkers on sensitive drafts. Many of them don’t say clearly what happens to the text you paste, and a privacy policy you can’t find is an answer in itself.

FAQs on Plagiarism Checkers

Final Remarks

Before you pay for a long subscription, check one representative draft and open the sources behind its matches. A report earns its price when it helps you find a missing citation or a passage that needs rewriting. For academic work, your institution’s rules decide the final call. For a blog post, I’d fix the source use before publishing, even when the overall score looks low.

Disclaimer: This site is reader-supported. If you buy through some links, I may earn a small commission at no extra cost to you. I only recommend tools I trust and would use myself. Your support helps keep gauravtiwari.org free and focused on real-world advice. Thanks. - Gaurav Tiwari