Free Plagiarism Checker

Find out whether your text already appears on the web. Every match links to the page where it was found, and you can download a report of the results.

A plagiarism checker is a software tool that scans text content to detect duplicate or copied material from other sources. Our free online plagiarism detector uses Claude, Anthropic's AI model, to search the web for the most distinctive sentences in your text and report the pages where they already appear.

Plagiarism can have serious consequences in academic, professional, and publishing contexts.

How to Use Our Free Plagiarism Checker

  • Enter Your Text: Paste your content, upload a .txt file, or enter a URL to check
  • Click Check: Claude searches the web for your most distinctive sentences and checks every match
  • Review Results: See your originality score, highlighted matches, and potential sources
  • Download Report: Get a detailed plagiarism report for your records or submission

Why Check for Plagiarism?

  • Maintain Academic Integrity: Students and researchers must submit original work to avoid penalties
  • Protect Your Reputation: Writers and bloggers need unique content to build credibility
  • Avoid Legal Issues: Copyright infringement can lead to legal action
  • Ensure Quality: Original content demonstrates expertise and thought leadership

How Our Plagiarism Detector Works

Each check runs in these steps:

  • Web Search: Claude searches the web for your most distinctive sentences, quoting them exactly
  • Verification: SaveDelete opens each page to confirm the passage is on it; a page it can't open leaves the match unconfirmed
  • Sources: Each match links to the page where the passage was found
  • Scoring: The originality score is the share of your words outside matched passages

Tips for Avoiding Plagiarism

  • Cite Your Sources: Always give credit when using others' ideas or words
  • Paraphrase Properly: Rewrite ideas in your own words, not just synonym swaps
  • Use Quotation Marks: Direct quotes should be clearly marked and attributed
  • Keep Track of Sources: Maintain a bibliography as you research
  • Check Before Submitting: Use our plagiarism checker to verify originality

Related Free Tools

What happens when you run a check

When you press Check for Plagiarism, Claude, Anthropic's AI model, gets your whole text. Each check takes 20 to 1,500 words and up to 12,000 characters.

  1. Claude runs up to five web searches. It picks the most distinctive sentences and phrases in your text and searches for them in exact quotes.
  2. It reports a passage only when a page in those results has the same wording, or nearly the same. It is told to skip common phrases, idioms, well-known quotations and widely stated facts.
  3. SaveDelete checks each passage. It must be at least four words long, appear in your text, and name a page from the search results.
  4. SaveDelete opens each source page and splits the passage into runs of five words. If at least half of those runs are on the page, the match is confirmed. If fewer than half are there, the match is dropped.
  5. If a page can't be read, the match stays but is marked unconfirmed. Errors, PDF files and pages slower than six seconds cause this.

If none of the searches come back, you get an error message, not a score.

How your score is worked out

The score counts words. SaveDelete finds the share of your words inside matched passages, and your originality score is 100 minus that share.

Say you check 400 words and one 60-word passage matches. That is 15% matched, or 85% original.

Unconfirmed matches count too. Every word in a matched passage counts in full, whatever its similarity figure.

For a confirmed match, the similarity figure is the share of its five-word runs found on the source page. For an unconfirmed match, it is Claude's own estimate.

Behind the scenes, SaveDelete flags a text as plagiarized when more than 30% of its words are matched. On the page, that is where the score drops below 70% and turns orange.

The downloaded report lists each match with its source, similarity and link, plus your full text. It doesn't say which matches were unconfirmed, so note those before you share it.

What potential plagiarism means

Highlighted passages are marked potential plagiarism, not plagiarism. A match shows that the same words appear on another page. It doesn't show who wrote them first, or whether you gave credit.

The University of Reading's guide to similarity reports lists correctly quoted and referenced material and common phrases as normal matches.

Two cases surprise people:

  • Quotes you cited. The check doesn't look for quotation marks or references, so a correctly cited quote can still be highlighted.
  • Your own pages. The check doesn't skip any site. If your text is already online, your own page can come up as the source.

What this checker can't see

The check only sees the public web, through at most five searches. That leaves gaps:

  • Long texts. A long text gets the same five searches as a short one. For a closer look, check one section at a time, within the limit of five checks an hour.
  • Anything behind a login. SaveDelete opens pages without signing in, so private documents, subscription journals and course pages are out of reach.
  • Student paper databases. Turnitin's standard paper repository, for example, checks papers against other institutions' student submissions. This tool has no such database.
  • Reworded text. The check looks for the same or nearly the same wording, so a thorough paraphrase will usually pass.
  • Files and images. Upload reads plain .txt files only, so paste text from a PDF or Word file. To trace where a picture appears online, use reverse image search.

It doesn't detect AI-generated content

This plagiarism checker has no AI detector. It reports only wording it finds on web pages. If an AI tool writes new wording that isn't on any page, the text can score 100% original.

Plagiarism and AI writing are different problems. Purdue OWL describes plagiarism as presenting another person's words or ideas without credit. Rules on AI use can be separate. The University of Glasgow's rules, for example, bar AI-produced content in students' work unless it is acknowledged. Check your school's or publisher's rules on AI use.

Common types of plagiarism

University writing guides describe several types of plagiarism. This tool catches some better than others.

  • Direct plagiarism: copying a section word for word, with no quotation marks and no credit. The checker is built to find this, if the source is public.
  • Mosaic plagiarism, or patchwriting: borrowing phrases without quotation marks, or swapping in synonyms while keeping the source's structure. Bowdoin College counts it as dishonest even with a footnote. The checker catches it only where enough five-word runs survive.
  • Paraphrase without credit: restating someone's idea in new words without citing it. Purdue OWL counts ideas, not just words. The checker usually misses this.
  • Self-plagiarism: reusing your own earlier work without permission, such as one paper for two classes. The checker finds it only if the earlier version is public.
  • Accidental plagiarism: forgetting a citation, misquoting a source or paraphrasing too closely. Bowdoin says it carries the same range of consequences as other plagiarism.

How to fix a flagged passage

  1. Open the source link beside the match and read the passage there.
  2. If you need the exact words, put them in quotation marks and cite the source.
  3. If you don't, rewrite the idea in your own words and structure. Purdue OWL suggests writing from memory, without looking at the original. Then cite the source anyway, because the idea came from it.
  4. Check the revised passage again, then run it through our grammar checker to catch slips.

Citation basics

Purdue OWL describes three parts to a citation. A signal phrase such as "According to Smith" introduces the source. An in-text citation closes the borrowed material. A full entry in your reference list tells readers where to find it.

Common knowledge doesn't need a citation. Purdue OWL's rule of thumb is that common knowledge appears in at least five credible sources. If you aren't sure, cite it.

Frequently asked questions

Is this plagiarism checker really free?

Yes. The plagiarism checker is free and needs no registration. Each check covers 20 to 1,500 words (up to 12,000 characters), and each visitor can run up to 5 checks an hour and 15 a day, because every check runs real web searches.

How accurate is the plagiarism detection?

Claude, Anthropic's AI model, runs up to five web searches for the most distinctive sentences in your text. SaveDelete opens each page it names to confirm the passage is there. A match on a page it can't open is kept, marked unconfirmed, and still counts. Paraphrases and unindexed pages can be missed, so use it as one tool in your verification process.

Can I check academic papers and essays?

Yes, for essays, assignments and articles of up to 1,500 words per check. Split longer work into sections. The check searches the public web only, so it can't see subscription journals or databases of student papers.

What file formats are supported?

Paste your text, upload a plain .txt file (up to 5MB), or enter a webpage URL to check that page's text. PDF and Word files can't be uploaded, so copy their text and paste it in.

Is my content saved or stored?

SaveDelete doesn't store your text. To check it, the text is sent to Anthropic's Claude API, which searches the web for its most distinctive sentences. Your check history stays in your own browser, and you can clear it at any time.

What does the originality score mean?

The originality score (0-100%) is the share of your words outside matched passages. 90% or more shows green, 70-89% yellow, 50-69% orange and below 50% red. A match can still be a correctly cited quote, so read each one before you decide.

Can I download a plagiarism report?

Yes. After each check you can download a plain-text report. It lists your score and word count, each matched passage with its source, similarity and link, and your full text.

How is this different from Turnitin?

This checker is free with no sign-up, and it searches the public web for your text. Tools that schools use, such as Turnitin, also compare work with stored student papers, which this checker can't see. We don't add your text to any database.