How modern plagiarism detection works
Older checkers used exact-string matching — they only flagged identical text. Modern AI-assisted checkers also detect paraphrased or restructured passages by comparing semantic embeddings.
This means swapping a few synonyms no longer hides copied content. Detection now looks at meaning, not just letters.
Step-by-step
- 1Open the Plagiarism Checker.
- 2Paste up to ~2,000 words at a time.
- 3Click Check plagiarism.
- 4Review the overall similarity score and the highlighted source matches.
- 5Cite the sources, rewrite the flagged passages, or remove them.
What counts as plagiarism
- Copying paragraphs verbatim without citation.
- Heavy paraphrasing of someone else's structure without credit.
- Self-plagiarism — re-using your own published work without disclosure.
- Stitching together multiple uncited sources into one piece ("mosaic plagiarism").
What doesn't
- Common factual statements that everyone phrases similarly.
- Properly quoted and cited material.
- Generic boilerplate like product descriptions or step-by-step UI labels.
How AI plagiarism heuristics actually work
Traditional plagiarism checkers (Turnitin, Copyscape) compare your text against an indexed database of academic papers and web pages. AI heuristic checkers take a different approach — they flag sentences that read as common phrasings: overused stock transitions, generic definitions, boilerplate intros and conclusions, and patterns that statistically appear in millions of indexed pages even without exact-match copying. The result is a per-sentence verdict, not a single percentage against a fixed corpus.
Both approaches are useful. Database lookups catch exact and near-exact reuse. Heuristic checks catch the more subtle problem of writing that's not technically copied but reads as templated or AI-generated. For a thorough check before submission, run both.
When to trust the score and when to ignore it
- Trust low originality scores: if more than 30% of your sentences flag, the text needs substantive rewriting.
- Ignore individual flags on quoted material, common idioms, and technical definitions — they will always flag and that's expected.
- Pay attention to flags on transition phrases like "in conclusion," "it is important to note that," "in today's world" — these are AI-generated tells and they hurt how readers and editors perceive the writing.
- Re-run after rewriting. A score that drops from 55 to 80 after edits is meaningful improvement.
Citing sources the right way
If your text legitimately quotes or paraphrases a source, cite it inline rather than hoping the checker forgives the overlap. Even a casual reader notices a sentence that reads like it came from elsewhere. Citing converts the issue from "is this plagiarism?" into "this writer did their homework" — exactly the inversion you want.
FAQ
- Is the Plagiarism Checker free?
- Yes — check up to 2,000 words per request, no signup.
- Does it search behind paywalls?
- It searches the open web. Paywalled academic databases require a specialised tool like Turnitin.
- Will it detect AI-generated text?
- Plagiarism and AI detection are different problems — use our AI Detector for the second one.
- Is my text stored?
- No — queries are run and discarded.
- What's an acceptable similarity score?
- For academic essays, generally under 15%. For blog posts, near 0% (excluding direct quotes).
- Can I check in other languages?
- Yes — best results in English; supported in major languages.