Plagiarism Detector — Heuristic Originality Check for Drafts
Heuristic plagiarism check: highlights repeated phrases, shows duplicate-content patterns. Pre-Turnitin self-check.
About Plagiarism Detector (Academic)
A plagiarism detector compares a piece of writing against a corpus of existing text and flags spans that closely resemble sources, helping students self-check originality before submitting and helping educators triage suspect work. The ZTools Plagiarism Detector is a heuristic, browser-only tool: it analyses internal duplication (repeated phrases, copy-paste patterns), surfaces common idiomatic shortcuts, and gives a structural originality score — useful as a pre-submission self-check, but not a substitute for institutional services like Turnitin or iThenticate which compare against private + published corpora a browser tool cannot access.
Use cases
- Pre-submission self-check. Before turning in an essay, run it through the detector to catch unintentional copy-paste from notes (which originally came from sources). Cleans up forgotten quotation marks and missing citations.
- Group writing review. For collaboratively-written documents, identify sections that look mass-pasted from a single team member's sources rather than synthesised, suggesting edits before submission.
- Editing for voice consistency. Flags abrupt changes in writing style or vocabulary, which often indicate either AI-pasted text or a switch in author. Helps polish a unified voice.
- Teacher triage tool. For first-pass review on a stack of essays, the detector surfaces high-internal-repetition cases worth checking more carefully with institutional tools.
How it works
- Paste the document. Text area accepts the full essay or paper. No upload, all client-side.
- Tokenise to n-grams. Splits into sliding 5-9 word phrases (n-grams), normalised (lowercase, punctuation removed).
- Compute repetition profile. Counts how often each n-gram repeats; high-frequency n-grams either repeat naturally (style) or signal copy-paste from a single source.
- Detect common phrases. Compares against a small embedded corpus of high-frequency English idioms — flags filler, not plagiarism.
- Surface structural flags. Heuristic originality score, list of suspicious spans, and recommendations: add citation, rewrite in own words, or accept (idiom).
Examples
Input: Essay with 3 spans copy-pasted from notes
Output: Detector flags 3 spans as "high internal duplication"; recommends adding citation or rewording.
Input: Original 1500-word essay
Output: Originality score 92%; minor repeats are common idioms ("on the other hand", "in conclusion") — accepted.
Input: Mostly-AI-generated draft
Output: Detector cannot directly identify AI text — but flags unusually low style variance and repetitive sentence structure as signal.
Frequently asked questions
Is this as accurate as Turnitin?
No. Turnitin compares against a private corpus of millions of student papers + published books + the web. A browser tool cannot replicate that. This is a self-check, not an audit.
Does it work for AI-generated text?
Indirectly — AI text often has uniform style and reduced vocabulary diversity. The detector surfaces structural cues but cannot confirm AI origin without specialised AI-detection models.
Will it false-positive on quotations?
Quoted material with proper quotation marks is downweighted. Unmarked quotations (forgot the quotes) get flagged — exactly the use case for self-checking.
What about paraphrasing?
Light paraphrasing (synonym swaps) often still leaves n-gram overlap; the detector flags it. Heavy paraphrasing (full rewrite of structure) typically passes.
Is my text uploaded?
No — entirely client-side. Privacy by design. The browser tab is the entire compute environment.
What is a "good" originality score?
For self-check purposes, 85%+ is usually fine; below 70% warrants careful review. Institutional thresholds vary widely by department.
Pro tips
- Use this tool first; only escalate to Turnitin or instructor review if the self-check shows real concerns.
- Always cite sources for ideas you read — not just for quoted passages. Paraphrased thought still belongs to the original author.
- When in doubt, cite. A paper with too many citations is corrected; a paper with too few risks academic-integrity action.
- Run the detector on each section independently; problems often concentrate in one paragraph copy-pasted from notes.
- For thesis-level work, submit to Turnitin via your institution before final submission — heuristic tools are not enough at that stakes level.
Reviewed by Ahsan Mahmood · Last updated 2026-05-05 · Part of ZTools.
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