What is the Plagiarism Checker?
This plagiarism checker does not scan the web, and it does not calculate an originality percentage — no free browser-based tool honestly can, because comparing text against the entire indexed internet requires a licensed, continuously crawled search index that costs real money to build and run. What this tool does instead, genuinely and verifiably, is two things: it finds passages repeated within your own document using n-gram shingling, and it builds exact-phrase search links for Google, Bing and DuckDuckGo from your most distinctive sentences, so you can check the wider web yourself with one click per sentence. Anything claiming to give you a free, instant "97% original" score against the whole internet is not doing what it says — this tool tells you plainly what it can and cannot do.
Why a licensed index matters: real plagiarism-detection services (the kind universities and publishers pay for) work by maintaining their own crawled copy of billions of web pages, academic papers and previously submitted student work, then comparing your text against that private database. Building and maintaining an index at that scale is a commercial undertaking, not something that runs for free in a browser tab. A tool that claims to check "the entire web" without that infrastructure is either quietly using a small, unstated subset of search results, or not actually checking anything — this tool avoids both problems by not making that claim at all.
An honest note on the data
Full-web plagiarism comparison needs a licensed search index. This tool runs local similarity checks and generates exact-phrase search queries you can verify yourself.
Why use a free plagiarism checker?
Honest about what it checks
No invented originality score, no vague "checked against billions of sources" claim. The tool tells you exactly which two checks it ran and shows you the evidence for each.
Finds real duplication within your document
Repeated 8-word-or-longer passages inside your own text — accidental duplication, recycled boilerplate, a paragraph pasted twice — are a genuine, verifiable signal this tool can compute with certainty.
One-click verification against the live web
Exact-phrase search links are generated automatically from your most distinctive sentences, so checking the actual web takes one click per link instead of manually copying and quoting each sentence yourself.
Shows the matching sentences side by side
Every internal match displays both sentences and the shared phrase, so you can judge for yourself whether it is a meaningful repetition or coincidental.
Nothing uploaded
Your document is analysed entirely in your browser. It is never sent to a server, which matters for unpublished drafts and confidential documents.
How do you use the Plagiarism Checker?
- 1
Paste your document
Works on anything from a paragraph to a full article. The check runs automatically as you type.
- 2
Review internally repeated passages
Any 8-word-or-longer phrase that appears more than once in your document is flagged, with both matching sentences shown side by side.
- 3
Open the generated search queries
Your longest, most distinctive sentences are turned into exact-phrase search links for Google, Bing and DuckDuckGo — open any of them to check that exact wording against the live web.
- 4
Judge the results yourself
A search hit does not automatically mean plagiarism — it could be a common phrase, a quotation you cited, or a source you are legitimately paraphrasing. Use the results as a starting point for judgment, not a verdict.
How accurate is it?
The internal-similarity check is exact and deterministic: the text is broken into overlapping 8-word shingles, and any shingle appearing more than once is a genuine, literal repetition inside your own document — there is no approximation in that count. The search-query builder is equally exact: it wraps your longest sentences in quotation marks to force an exact-phrase search, but the checking itself happens on the search engine's live index when you click through, not inside this tool.
- This tool has no visibility into the web, academic databases or any other document beyond the one you pasted. It cannot and does not report a percentage of your text that is "original" or "plagiarized" against outside sources — that number does not exist without a real search index behind it.
- The 8-word shingle length is a deliberate threshold: shorter shared phrases (like "in order to" or "on the other hand") are extremely common in ordinary writing and would produce false positives if flagged.
- Only 8 sentences of 8–26 words are turned into search links, chosen by length — very short or very long sentences make weaker exact-phrase search queries and are skipped.
- A phrase turning up in a Google search does not by itself prove plagiarism — check the source, the date, and whether you are the original author or the one who copied, before drawing a conclusion.
What should you know before using it?
What this tool checks, and what only a licensed, paid plagiarism service can actually do:
| Capability | Status here |
|---|---|
| Repeated passages within your own document | Yes — computed exactly using 8-word shingle matching. |
| Exact-phrase search links to check the live web | Yes — generated automatically, but you have to open and review each one yourself. |
| Comparison against a crawled index of the whole web | No — that requires a licensed search index this tool does not have. |
| Comparison against academic paper or student-submission databases | No — those are private, commercially licensed databases (e.g. Turnitin). |
| A single originality or plagiarism percentage | Not provided, on principle — any percentage claimed against sources this tool cannot see would be fabricated. |
Which tools relate to the plagiarism checker?
The plagiarism checker is one of 12 writing tools on this site. These are the ones most often used alongside it — either because they handle the next step in the same job, or because they answer a question this tool raises.
Online Proofreader
A clean pass for spelling, punctuation and structure before you circulate a draft — separate from, and not a substitute for, checking originality.
Text Summarizer
If you are checking a long document, use this to see which sentences carry the actual argument before manually reviewing search results for each one.
AI Content Detector
A different question entirely — this checks whether text resembles known sources, while the AI Content Detector reports statistical writing-pattern signals. Neither tool proves authorship on its own.
Paragraph Rewriter
If you find a passage you need to genuinely rewrite in your own words, this tool offers structural and word-choice suggestions — though real rewriting still requires understanding the source, not just swapping words.
When should you use a plagiarism checker?
Because the plagiarism checker runs entirely in your browser, it suits work you would not want to hand to a third-party server — client files, unpublished drafts, anything under an NDA. These are the situations people reach for it in most often.
Catching accidental self-duplication
Long documents edited across multiple sessions often end up with a paragraph pasted twice, or a boilerplate sentence repeated without the writer noticing — the internal check catches this reliably.
Verifying a specific quote or claim before publishing
Use the generated search links to check whether a striking phrase in your draft is actually a well-known quotation you should be citing, rather than original wording.
A first-pass check before a formal plagiarism service
Catch obvious internal duplication and check a handful of key sentences against the live web yourself before submitting a document to a paid, full-index service for the final check.
Checking your own content against accidental overlap
Writers reusing their own past phrasing across multiple articles can use the search-query links to see where a sentence has appeared before, including on their own previously published pages.
Frequently asked questions
Does this plagiarism checker scan the whole internet?
What percentage of my text is plagiarized?
How does the internal-repetition check work?
How do the search-query links work?
Why can't a free browser tool check the whole web for me?
If a search result matches my sentence, does that prove plagiarism?
Is my document uploaded anywhere?
Is the plagiarism checker safe to use?
This tool runs entirely inside your browser. Your text, files and settings are processed on your own device and are never uploaded to our servers — there is nothing for us to store, log or leak. You can confirm it yourself: open your browser DevTools, switch to the Network tab, and use the tool. You will not see an upload request. It also means the tool keeps working if your connection drops mid-task.
Read more about plagiarism checker
How to Rewrite Articles for Unique Content
Learn how to rewrite articles for unique content online. SEO-safe rewriting in seconds. Step-by-step guide with quality tips inside! No signup required, ever.
2 min read
How to Check Content for Plagiarism Online
Learn how to check content for plagiarism online. Scan billions of pages in seconds. Step-by-step guide with originality tips inside! No signup required, ever.
2 min read
How to Tell If Content Was Written by AI (Free 2026 Detection Guide)
Detect AI Content Fast with Trusted AI Detector Tools to Spot ChatGPT, Gemini & Claude-Written Text Accurately. Completely free, fast, and no signup required.
4 min read
More on the Smart SEO Toolz blog.
Need something this tool can’t do?
If you need a feature added, spotted something wrong, or want a custom tool or website built for your business, tell us. We read every message and we build what people actually ask for.
More tools
Tools that pair well with this one
Browse every category
- SEO Tools31
- Keyword Tools7
- Domain & IP Tools18
- Text Tools20
- Writing Tools12
- Image Tools31
- PDF Tools17
- Unit Converters14
- Calculators21
- Developer Tools13
- Generators16
- Design & CSS Tools6
- Games8
Looking for something else? See all 214 tools, browse the full site index or read the guides on our blog.