Paraphrase Quality Checker
Paste the passage you are paraphrasing on the left and your version on the right, press Compare, and see how many words they share, which runs of three or more words match exactly, and a similarity score from 0 to 100%. It compares only the two texts you give it — it does not search the web or any database, and it cannot detect plagiarism. Free, no sign-up, and nothing is uploaded.
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Tips for Effective Paraphrasing
- Read and understand first — Put the original away and write from memory.
- Change sentence structure — Rearrange clauses, combine or split sentences.
- Use synonyms — Replace key words with alternatives (but keep technical terms).
- Change voice — Switch between active and passive voice.
- Always cite — Even a perfect paraphrase needs an in-text citation.
How to Use the Paraphrase Checker
- Paste both texts. The original goes in the left box and your paraphrase in the right. Each box shows its word count.
- Press Compare. Editing either box clears the result, so press the button again after each change.
- Read the three numbers. The overall similarity score, the word overlap and the number of matching phrases. Under 30% is labelled Good paraphrase, 30–50% Needs more work, and over 50% Too similar to original.
- Check the highlights. Your paraphrase is shown with every word that sits in a matching run of three or more words shaded, and the matching phrases are listed. Rework those stretches in your own wording.
How the Score Is Worked Out
Both texts are lowercased, stripped of punctuation and split into words. Then:
- Word overlap = distinct words found in both texts ÷ distinct words in either text, as a percentage. It ignores how often a word repeats and where it sits.
- Matching phrases = identical runs of 3 or more consecutive words that appear in both texts. Each run is counted once, however long it is, so one shared 5-word sequence is one phrase and so is a 12-word one. Runs that overlap in your paraphrase are merged into a single phrase.
- Phrase penalty = 10 points per matching phrase (separate shared stretch), up to 40.
- Score = 60% of the overlap + the phrase penalty, capped at 100.
The formula is a transparent heuristic, not an institutional standard. No school, publisher or style guide defines a passing percentage. Two things push honest paraphrases up: shared function words (the, of, in) raise overlap whenever the topic is the same, and technical terms cannot be swapped out, so they repeat in a phrase even in a good rewrite.
What Makes a Paraphrase
A paraphrase restates a source’s idea in your own words and your own sentence structure, and it still needs a citation. Swapping a few words for synonyms while keeping the original’s structure — sometimes called patchwriting — is not enough, and the checker will usually show it as high overlap and many matching phrases. A reliable method is to read the passage, close it, write what it means from memory, and then compare. APA 7 requires the author and year for a paraphrase and encourages a page or paragraph number; see Do You Need a Page Number When Paraphrasing?. If a short phrase is truly distinctive, quote it instead — Paraphrasing vs. Quoting: When to Use Each explains how to choose.
What It Cannot Do
- It does not check plagiarism. It never looks at the web, journals or other students’ work. A low score does not clear a text of plagiarism, and a high one does not prove it.
- It does not read meaning. A paraphrase that distorts the source can score as well as a faithful one.
- It ignores accents and non-Latin text. Characters that are not letters, digits or underscores are stripped, so café becomes caf and text in other scripts is dropped.
- It cannot tell a technical term from copying. Consolidation of declarative memory will match in a faithful rewrite.
Worked Example
The original is a 20-word sentence: Sleep deprivation impairs the consolidation of declarative memory in young adults, especially when it occurs on the night after learning. Three versions:
| Paraphrase | Overlap | Matching phrases | Score |
|---|---|---|---|
| Young adults who skip sleep after studying remember facts less well, because the brain consolidates declarative memory overnight. | 23% | 0 | 14% — Good paraphrase |
| Lack of sleep damages the consolidation of declarative memory in young adults, particularly when it happens on the night after learning. | 65% | 2 | 59% — Too similar |
| Sleep deprivation impairs the consolidation of memory in young adults, especially when it occurs after learning. | 84% | 2 | 70% — Too similar |
The second version shows the usual mistake: three words swapped, structure kept. The first restructures the sentence and changes almost every word, so nothing matches. Whether it is faithful is for you to judge, not the checker: it adds a claim about the brain consolidating memory overnight that the source sentence does not make.
Which Tool Do You Need?
| If you want to… | Use |
|---|---|
| Check how closely your paraphrase echoes its source: shared words and matching phrases | This Paraphrase Checker |
| See exactly which lines were added, removed or kept between two drafts | Text Diff Checker |
Frequently Asked Questions
- What does the paraphrase checker do?
- It compares a source passage with your paraphrase and reports the word overlap, the number of matching phrases of three or more words, and a combined similarity score. It highlights the matching words in your paraphrase.
- Is this a plagiarism checker?
- No. It compares only the two texts you paste. It does not search any database or the web, so it cannot tell you whether your work matches another source.
- What similarity score is acceptable?
- There is no official figure. This tool labels under 30% a good paraphrase, 30–50% needs more work, and over 50% too similar. Treat the labels as a guide for the amount of rewording, and judge by whether your sentence structure and wording are your own.
- How are matching phrases counted?
- Each shared stretch of three or more consecutive words counts once, however long it is, and stretches that overlap in your paraphrase are merged. A single 6-word sequence is one phrase. Look at the highlighted words in your paraphrase to see where the shared stretches are.
- Do I still need to cite a perfect paraphrase?
- Yes. A paraphrase borrows an idea, so it needs an in-text citation and a reference-list entry in your citation style however different the wording is. Build the reference with the citation generator on the home page.
- Can I check a paraphrase of text in another language?
- Not reliably. The tool removes characters outside letters, digits and underscores, so accents and non-Latin scripts are altered or dropped.
- Is my text uploaded?
- No. The comparison runs in your browser and nothing is sent to a server.