Plagiarism Checker
Two modes: compare two texts, or check a single text sentence-by-sentence
Text to check — matched sentences highlighted in yellow
Matched sentences
What is plagiarism?
Plagiarism is the act of presenting someone else's words, ideas, or work as your own without proper attribution. It can be intentional — deliberately copying text — or accidental, such as forgetting to cite a paraphrase or quote.
In academic settings, plagiarism violates integrity policies and can result in serious consequences. In professional and publishing contexts, it can constitute copyright infringement. Even self-plagiarism — reusing your own previously published work without disclosure — is considered a form of plagiarism in many fields.
Types of plagiarism
| Type | Description | Example |
|---|---|---|
| Direct / verbatim | Copying text word-for-word without quotation or attribution | Copy-pasting a paragraph from Wikipedia |
| Paraphrasing | Rewording someone else's idea without citing the source | Changing a few words but keeping the same structure and meaning |
| Mosaic / patchwork | Mixing copied phrases with original text without attribution | Weaving Wikipedia sentences into your own paragraphs |
| Accidental | Unintentional plagiarism due to poor citation habits | Forgetting to add a reference for a paraphrase |
| Self-plagiarism | Reusing your own previous work without disclosure | Submitting last year's essay for a new assignment |
| AI-generated | Submitting AI-written content as original human work | Submitting a ChatGPT essay as your own |
How our plagiarism checker works
Choose a mode
Compare two texts — paste an original and a submission side by side. The tool splits both into sentences, normalises them, and calculates how many sentences from the submission appear in the original.
Web search mode — paste a single text and get a Google search link for every sentence, so you can verify each one manually against live web results.
Sentence tokenisation
The text is split into individual sentences at full stops, exclamation marks, and question marks. Short fragments under 5 words are ignored to avoid false positives on common phrases.
Similarity scoring
In compare mode, each sentence from the checked text is compared against all sentences from the original using normalised string matching. Sentences with over 70% word overlap are flagged as matches.
Results and highlighting
Matched sentences are highlighted in yellow in the checked text. The similarity score shows what percentage of sentences were found in the original. Each match also has a Google search link for independent verification.
How to avoid plagiarism
- Always cite your sources — whether quoting directly or paraphrasing, include a proper reference (APA, MLA, Chicago, etc.).
- Use quotation marks for direct quotes — any verbatim text must be enclosed in quotes and attributed.
- Paraphrase carefully — restate ideas in your own words and sentence structure, not just substituting synonyms.
- Keep good research notes — note where every idea comes from as you research, before you write.
- Run a check before submitting — use a plagiarism checker on your own work to catch accidental overlaps.
- Understand your institution's policy — different fields and institutions have different standards for what constitutes plagiarism.
Frequently asked questions
Yes. The text comparison tool runs entirely in your browser — no API, no sign-up, no word limits. The web search mode generates Google search links that you click to verify; Google's search is free. There is no paid tier on this tool.
The compare mode is highly accurate for detecting direct copying between two texts. It matches sentences with over 70% word overlap after normalisation. It does not detect paraphrasing or synonym substitution — for that, use the web search mode and manually review the sources.
The compare mode checks against a text you provide. The web search mode generates a Google search for each sentence — Google's index covers the vast majority of the public web. True internet-wide plagiarism databases (like Turnitin) require paid subscriptions because they maintain proprietary indexed archives of academic papers.
Most universities accept up to 10–15% similarity (for properly cited quotes and references). Over 20% typically triggers a review; over 40% is usually considered plagiarism. However, policies vary significantly by institution — always check your specific guidelines. Our tool uses these thresholds as a guide for the verdict labels.
No. This tool detects text that is copied from another source — it does not determine whether text was written by an AI. AI-generated content that is unique (not copied from a specific source) would score 0% on this checker. For AI detection, dedicated tools like GPTZero are more appropriate.
No. All processing happens in your browser using JavaScript. Your text never leaves your device. ToolBase's servers never receive or store any text you enter into this tool.