Verbatim and paraphrase detection
Finds copied sentences and reworded ones — the matches that simple string comparison misses.
Plagiarism checker built for research papers and theses
Upload a manuscript as PDF, DOCX or TXT and PlagLab checks it the way an editor would: verbatim overlap, paraphrased passages, AI-written sections and the integrity of your citations — against open scholarly literature including OpenAlex, arXiv, Crossref and Semantic Scholar. You get a highlighted report that shows exactly which sentences matched and where they came from.
Free account: 50 tokens every month · no card needed
What it does
Features of the Plagiarism Checker
AI-authorship signal
Flags passages that read machine-written, shown separately from similarity so the two are never confused.
Citation integrity
Checks whether matched passages are properly quoted and cited, so legitimate quotations are not counted against you.
Scholarly sources
Searches open literature live — OpenAlex, arXiv, Crossref, Semantic Scholar, Wikipedia, Project Gutenberg and the Internet Archive.
Highlighted report
A professional PDF report with similarity and AI passages highlighted in different colours, ready to share with a supervisor.
Private case history
Your reports are filed in your own account's docket, visible only to you.
How it works
From draft to result in 4 steps
- Upload the manuscriptDrop a PDF, DOCX, DOCM or TXT file — up to about 30 MB. Checking starts immediately.
- Choose the depthA standard check covers most papers; the deep and maximum sweeps read more candidate sources in full for a thesis.
- Read the evidenceEvery match links to its source with the overlapping text side by side, so you can judge it rather than trust a number.
- Fix and re-checkRevise, cite or quote the flagged passages — or use the Remediation Lab — then run the check again.
Who it's for
Built for the people who write research
PhD candidatesCheck each thesis chapter before it goes to your supervisor.
ResearchersCatch unintentional overlap before a journal's own check does.
SupervisorsReview a student draft with evidence, not just a percentage.
EditorsScreen submissions for copied and AI-generated passages.
Questions
Frequently asked questions
Is the plagiarism checker free?
Every tool opens on the free plan: a free account gets 50 tokens every month. Longer documents, downloads and some advanced modes need a paid plan — the tool tells you when you reach one.
What similarity percentage is acceptable for a research paper?
There is no universal number. Journals look at what matched: properly quoted and cited text, standard method phrasing and your own references are normal; long uncited passages are not. Read the matches, not just the total.
Does it detect paraphrasing, not just copy-paste?
Yes. PlagLab compares meaning as well as wording, so reworded passages from a source are flagged alongside verbatim copies.
Will my paper be stored?
Your report is kept in your private case history so you can reopen it. Checked manuscripts are also kept in PlagLab's private comparison vault — that is how a later copy of the same text gets caught.
Is this the same as Turnitin or iThenticate?
It is an independent checker that searches open scholarly sources. Publishers and universities may run their own licensed tools as well; checking with PlagLab first helps you fix problems before submission.
Related
Tools that pair well with it
AI Content Detector
Check whether text reads AI-written — and see why. Explainable score, per-sentence heatmap, batch files and an exportable report.
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Paraphrasing Tool
Paraphrase academic text in eleven modes and seven tones. Click any sentence for fresh rewrites, keep citations frozen and compare versions side by side.
Learn more →
Citation Generator
Turn a DOI, title, author, ORCID or topic into real, formatted citations in APA, MLA, Chicago or BibTeX — from indexed literature, with links.
Learn more →
Try the Plagiarism Checker now.
Open it in your browser — nothing to install.