Plagiarism Checker — Repetition & Text Similarity
Detect repeated phrases and duplicate sentences in your writing, or compare two documents for text similarity. All analysis runs in your browser — your text is never sent to any server.
⏱ 6 min read · Complete guide below
Enter at least 10 words to analyse.
This tool checks for repetition and similarity within the text provided. It does not search the internet or external databases.
How the Plagiarism Checker Works
- 1Choose Repetition Check (single text) or Text Similarity (two texts).
- 2Paste your text into the input area(s).
- 3The tool scans for repeated 4-word phrases and duplicate sentences and displays a repetition score.
- 4Review the flagged phrases and rewrite overused sections to improve originality.
Repetition vs. Internet Plagiarism
This tool checks your writing for internal repetition and similarity to another document you provide. It does not crawl the web. For submitting academic work, also run your paper through your institution's recommended plagiarism service (Turnitin, iThenticate, or similar) which compares against web pages, published papers, and student submission databases.
What Actually Counts as Plagiarism
Plagiarism is presenting someone else's words, ideas, or work as your own without proper credit, and it takes more forms than most people realise. The obvious form is direct copying — lifting text word for word without quotation marks or a citation. But it also includes mosaic plagiarism, where you weave copied phrases into your own sentences; inadequate paraphrasing, where you swap a few words but keep the original structure; and even self-plagiarism, reusing your own previously submitted work without permission. The common thread is attribution: the issue is not that you used a source, but that you failed to make clear it was a source. Understanding this is the first step to writing that is genuinely your own.
How to Paraphrase Properly
Good paraphrasing is not a thesaurus exercise. Simply replacing words with synonyms while keeping the original sentence structure is still plagiarism, and it is exactly the kind of surface similarity a checker catches. The reliable method is to read the source, set it aside, and then write the idea from memory in your own words and your own structure — checking afterwards that you have captured the meaning accurately. Then, crucially, cite the source anyway. Paraphrasing changes the words; it does not remove your debt to the original author's idea. Use the Text Similarity mode here to compare your paraphrase against the source: a low score means you have genuinely rewritten it, while a high score is a warning to start over.
Why Reducing Repetition Improves Your Writing
Beyond plagiarism, the repetition check is a genuine writing tool. Unintentionally reusing the same phrases makes prose feel flat and padded, and it is often a sign that a point is being restated rather than developed. When the tool flags a recurring phrase, treat it as a prompt to vary your vocabulary, tighten a redundant passage, or combine two sentences that are making the same point. Writing with a lower repetition score tends to read as more precise and more confident — a benefit that has nothing to do with academic integrity and everything to do with quality.
Tips for Original Writing
Check your own draft first
Run your draft through Repetition Check before submission. Flagged phrases are often signs of copy-paste habits, unintentional self-plagiarism, or simply weak vocabulary variety.
Compare paraphrases
Paste your paraphrase and the original source into Text Similarity mode. A similarity score under 25% suggests the paraphrase is sufficiently original. Above 50% means you should rewrite more substantially.
Paraphrase, then cite
Putting source material into your own words is not enough on its own — you must still cite the original. Plagiarism is about attribution, not just word-for-word copying.
Use synonyms strategically
If the checker flags a recurring phrase, look for a technical synonym or restructure the sentence. Variety in phrasing is also a sign of a richer vocabulary to an instructor.
Frequently Asked Questions
Does this check against the internet?
No. This tool checks for repetition within your own text and similarity between two texts you provide. It does not search the web or any external database. For full web-based plagiarism detection, use a service like Copyscape or Turnitin.
What does the Repetition Score mean?
The repetition score estimates the percentage of your text that consists of repeated 4+ word phrases. A score below 15% is normal. Above 35% suggests significant repetition that may weaken your writing or indicate over-reliance on a source.
What is the Text Similarity mode?
Text Similarity compares two texts you paste and computes a cosine similarity score based on shared 3-word phrases (trigrams). 0% means no shared phrasing; 100% means identical texts.
Is my text stored or sent to any server?
No. All analysis runs client-side in JavaScript. Your text never leaves your device. This tool is completely private.
What counts as a "duplicate sentence"?
Any sentence of 4 or more words that appears more than once in your text is flagged as a duplicate. Intentional repetition for rhetorical effect (anaphora) may be flagged — use your judgment when reviewing results.
How can I reduce my repetition score?
Identify the flagged phrases in the results panel. Replace repeated terms with synonyms, restructure sentences to use different phrasing, or remove redundant sections entirely.
Is self-plagiarism really a problem?
Yes, in academic and professional contexts it can be. Submitting the same essay for two different courses, or reusing large portions of a previous paper without disclosure, is generally treated as academic misconduct because the work is being presented as new when it is not. If you want to build on your own earlier work, the safe approach is to cite it just as you would any other source, or to check with your instructor first.
Does using an AI writing tool count as plagiarism?
It can, depending on your institution's rules. Passing off AI-generated text as your own original work is considered a form of plagiarism or academic dishonesty in many schools, and a growing number now require you to disclose or cite AI assistance. Policies vary widely, so check the specific rules for your course. Regardless of the tool used, the underlying principle is the same: represent honestly who and what produced the work.
Why is my paraphrase being flagged as similar?
A high similarity score usually means your rewrite is too close to the original — often because you kept the same sentence structure and only swapped a few words, which is called "patchwriting" and still counts as inadequate paraphrasing. Read the source, look away, and rewrite the idea from memory in your own structure, then compare again. The score should drop substantially once the phrasing is genuinely yours.
Can this tool guarantee my work will pass Turnitin?
No. This tool checks for internal repetition and similarity between texts you supply; it does not compare your writing against the web, published papers, or student databases the way institutional services like Turnitin do. It is excellent for cleaning up your own draft and verifying paraphrases before submission, but it is a complement to — not a replacement for — whatever service your school actually uses.